Tag Archives: Beach of the Month

A Tale of Two Beaches: Tompire Bay, NE Trinidad; By John Weber, William Neal & Jeanette Arkle

Fig.-9-scarped-upper-beach-and-sargassum

By John C. Weber and William J. Neal, Department of Geology, Grand Valley State University, Allendale, MI, and Jeanette C. Arkle, Department of Geology, University of Cincinnati, Cincinnati, OH;

Trinidad, West Indies, has many beautiful beaches (IMA, 2013), and among the most interesting are those of the Northern Trinidad coast. Along the coast an east-west range of mountains, the Northern Range, emerges from the sea to peaks over 900 m in elevation (Fig. 1).

The shoreline of sea cliffs and rocky headlands is punctuated by both pocket beaches and short linear beaches associated with small river mouths. Tompire Beach, a particularly spectacular linear beach, is located along the northeast coast, near the village of Redhead (Cumana), off of Toco Main Road (Fig. 1, inset).

Tompire Beach, and the uniqueness of the geology of the Northern Range, have drawn the senior author to this location several times over the last 25 years. Here, an ancient beach has been uplifted out of the sea and is now perched ~20 m above the modern sands of Tompire Beach(Fig. 2).The preservation of this feature presents a unique opportunity to compare factors that shape the beach and, in turn, how an ancient beach can serve as direct markers for dynamic change.

“The “two beaches” provide an opportunity to compare the modern and ancient deposits.”
— J.Weber, W.Neal & J.Arkle

Two Beaches: Modern & Ancient

The present beach is a gentle arcuate strip extending north from Pt. Playa to another rock headland, a little over 0.8 km in length with the mouth of the Tompire River located about midway along the beach. At the mouth of the Tompire River the beach forms a spit-like emergent sand bar across the river mouth (Fig. 3).

The river mouth is sometimes closed in the dry season, but then breaks through to form its ocean outlet in the wet season. During storms the barrier bar is overwashed by waves and beach sand is transported across the bar into the lagoon.

The rugged shoreline has evolved under the influence of several factors. The spectacular rock structures exposed in the sea cliffs attest to ancient mountain building, and uplift in more recent time. The latter resulted in the raised marine terrace, capped by the fossil beach. This wave-cut platform stands about 20 m (>65 ft) above the present beach and modern-day sea level (Figs. 2 and 4), and has been cultivated for copra (dried coconut) production. The “two beaches” provide an opportunity to compare the modern and ancient deposits. For example, the internal structures (e.g., laminae and bedding) are similar (Figs. 5 and 6).

Modern Tompire Beach is a pebbly to coarse sandy beach, with abundant metamorphic rock fragments. Generally, the pebbles with abundant quartz veins are the ones that survive the vigorous attack by the strong Atlantic waves. The ancient beach is of similar composition, differing mainly in the sediments’ brown color due to staining by groundwater (Figs. 2 and 6). This ancient beach deposit has been recently dated at about 30,000 years old, using OSL (optically stimulated luminescence) (Arkle et al., 2015).

Modern Beach Sculptors

On a regional scale, imagine the island of Trinidad rolling on a north-south axis with the western side sinking and the eastern side rising. In a broad sense, western Trinidad is submergent, while the eastern side is emergent. The western coast of Trinidad is heavily embayed, characterized, in part, by extensive shorelines of mangrove swamps, and fewer beaches. The climate is dryer, less windy, and faces the Caribbean Sea and Gulf of Paria; areas of lower wave energy. The submergent pattern is also apparent along the north coast where pocket beaches become more pronounced and abundant to the west where tectonic sinking is greater (Fig. 1). Technically, this relative sinking versus rising is related to Plate Tectonics, driven by right-lateral transform tectonics at a pull-apart step-over, and/or over a deep lithospheric tear that is propagating eastward (Weber et al. 2010).

A second factor in the shaping of the emergent northeastern shore is that the eastern end of the Northern Range faces head-on into the strong easterly trade winds which generate an almost constant swell which, together with storms, generates a high-energy wave regime from the western Atlantic Ocean. Although the tidal range is not great, many of the narrow beaches are submerged at high tide, and waves are a dominant erosional force. This setting also results in a different climate than that of the western parts of the island. The annual rain fall (~5 m/yr) is much higher, and the land is covered in dense and lush tropical vegetation. The higher runoff is reflected in small rivers and streams coming down to the shore, and usually marked by somewhat more robust beach development. Local geology also is a factor in that the folded rocks of varied composition erode at different rates, producing an irregular shoreline of varied elevation. Tompire Bay’s beach is an example of the latter (Fig. 7).

Leatherback Sea Turtles & Sargassum Wrack

The northeast coast of Trinidad, including Tompire Bay, is a nesting ground for endangered leatherback sea turtles (Dermochelys coriacea). Programs instituted some years ago appear to be working as there has been a resurgence in the number of nesting turtles in the last few years. During nesting season Tompire Beach is patrolled at night for nest protection.

In 2011, unusual, thick accumulations of Sargassum seaweed on the beaches in the Eastern Caribbean were noted, and again in 2014. (See “Why is so much brown seaweed washing ashore?” Guardian and “A different look at Sargassum seaweed;” The Trinidad Express).

“The width of the continuous Sargassum wrack line, and its thickness (up to 2 m+) interfered with the turtles’ access to the beach.”
— J.Weber, W.Neal & J.Arkle

These massive amounts of seaweed are thought to be occurring because the range of areas in which the plant grows has increased, and is now growing where it can be picked up by currents in the western Atlantic and eastern Caribbean and carried to these islands. There is a preliminary suggestion that the change may be due to global warming which is a strong possibility as Sargassum needs nutrients and high water temperatures. Perhaps warming of the tropical ocean is changing habitats.

During the summer of 2015, large amounts of the seaweed were accumulating on Tompire Beach as massive wrack lines (Figs. 8, 9, and 10). Wrack lines are common on this beach, and the accumulations of drift wood at the back of the beach attest to the highest levels reached by storm waves (Fig. 8), however, the massive amounts of seaweed is a new phenomenon. The width of the continuous Sargassum wrack line, and its thickness (up to 2 m+) interfered with the turtles’ access to the beach. (Figs. 9 and 10) The sea turtles were forced to travel and nest up river on its sandy banks and on the back side of the barrier bar (Fig. 11).

Ancient Processes & Archives: Emergence of a Mountain Range

The back-beach sea cliff has some of the best rock exposures in the region, kept bare by wave action and mass wasting (Figs. 7 and 12). The spectacular folds (anticlines and synclines) are obvious even to the non-geologist. Three generations of folds and faults have been documented and studied in detail by Weber and Ferrill (2002). The dominant rock types are meta-sedimentary slates and meta-sandstones. These rocks have Mesozoic depositional ages and Cenozoic metamorphic ages (Weber et al. 2001). The composition of the present quarzites and slates, cut by veins of quartz, reflect the original sedimentary rocks that were shales and quartz sandstones. These rocks are the immediate sources for the beach sediment (Figs. 5 and 12), as well as material flushed down the Tompire River.

Lessons from the Two Beaches

The unique juxtaposition of a modern beach and the preservation of it’s older counterpart perched above, not only make for a beautiful remote setting, but retains an archive of the dynamic environment that shaped them both. Change is the rule, yet the physical conditions that shaped the two beaches are similar. The mountains evolved, the beaches have evolved. Natural change is the rule. But like the turtles, we must cope with such change without altering the natural habitat.


References

  • Arkle, J.C., Owen, L.A., Weber, J., Moonan, M., and Enkelmann, E., 2015, Late Neogene-Recent Evolution of the Northern Range, Trinidad, presented at 2015 Meeting, Caribbean Geological Conference, Port of Spain, Trinidad, 17-21 May.
  • Institute of Marine Affairs, 2013, A Guide to the Beaches and Bays of Trinidad and Tobago: Institute of Marine Affairs, Chaguaramus, Trinidad, West Indies, 113p.
  • Weber, J., Saleh, J., Balkaransingh, S., Dixon, T., Ambeh, W., Leong, T., Rodriguez, A., and Miller, K., 2011, Triangulation-to-GPS and GPS-to-GPS geodesy in Trinidad, West Indies: Neotectonics, seismic risk, and geologic implications, Journal Petroleum and Marine Geology, v.28, p.200-211, doi:10.1016/j.marpetgeo.2009.07.010.
  • Weber, J.C. and Ferrill, D., 2002, Structural geology of the Tompire Bay outcrops, eastern Northern Range, Trinidad, in, Jackson, T. A. (Ed.), Caribbean Geology Into the Third Millennium, 87-95, UWI Press.
  • Weber, J.C., Dixon, T.H., DeMets, C., Ambeh, W. B., Jansma, P., Mattioli, G., Saleh, J., Sella, G., Bilham, R., and Perez, O., 2010, GPS Estimate of relative motion between the Caribbean and South American plates, and geologic implications for Trinidad and Venezuela, Geology, 29, 75-78.
  • Weber, J.C., Ferrill, D., and Roden-Tice, M., 2001, Calcite and quartz microstructural geothermometry of low-grade metasedimentary rocks, Northern Range, Trinidad, Journal of Structural Geology, 23, 93-112.

Asilah, Morocco: A Coastal Town Seeking Modernity; By Celie Dailey

saf-2

By Celie Dailey;

Asilah (also Assilah or Arzila) is a beautifully revived town on the Atlantic coast of Morocco whose medina is white washed every year in preparation for its annual arts festival. (1) Within the oldest part of the town, its medina, walls get adorned with murals along the pedestrian-only streets. The Moussem International Cultural Festival facilitates the city’s improvement budget for the year and many residents depend on the income for their livelihood too. “…Asilah has become, over the past thirty years, a city of art and culture par excellence, thanks to its cultural Moussem,” (translated from French) the newspaper Aujourd’hui reported. (2) The festival occurs each summer with a variety of activities including concerts, film screenings, and poetry readings.

Mohammed Benaissa, returning to his hometown in 1968, with friend Mohammed Melei, a painter and the president of the Moroccan Painters Association, spearheaded improvement of Asilah with diligent community members. Rehabilitation of the city began with a trash collecting program, simply organizing a pick-up schedule at first, then expanded into other vital infrastructure projects and renovations of homes, mosques and other historic buildings. (3, 4)

“Outside the medina walls lapped by ocean tides, there is a craggy shore with bright green algae growing on its eroded rocks. To the north, there are wide, flat sandy beaches but to the south, cliffs and caves are found on shoreline.”
— Celie Dailey

In 1978 with the guidance of the Aga Khan Development Network, water, sewage and electricity improvements were implemented. The roads of the medina are patterned with curved pavers which Melei suggested to add visual interest, his reasoning that “the children of the town should have something beautiful to walk on.” (4) Jetties and a harbor were constructed, as well as a public beach as part of the restoration and rehabilitation process. Projects continue to bring vibrancy and a sustained tourist economy to Asilah.

Municipal plans are made through a town council, local craftsmen and construction workers are hired for projects, and financial aid is given to the poor to restore their homes.(4) Benaissa was insistent on improvements made with the input of the people. To first color the white walls of the medina, eleven artists were invited to paint murals in 1978, along with children and older people, involving the whole town in the project. This began the tradition of decorating the walls.

Walking on the beach north of the medina, a harbor where a few boats sit is protected by jetties, made from rocks and dolosee, cement poured into complex geometric forms which interlock. Along the main avenue near the shore are piles of building rubble and debris, a sign that Asilah is still undergoing change. On an early walk along the main route toward the port and medina, only a few souls were out when I photographed.

Inside the medina, its shops had lovely handcrafted goods, new and old, from around the country including jewelry, genuine antiques, and fine shoes and clothing. Blue and teal frequently accent doors and architectural ornaments in the White City.

The surrounding urban area of Asilah has restored neighborhoods, at times the architecture feeling very clean and modern. A commercial district has a variety of restaurants, cafes, bakeries, outdoor food vendors, stores selling factory-made clothing catering to locals, and thrift shops selling old electronics and household items. A visit to a bath house in the winter was absent of any other travelers.

Outside the medina walls lapped by ocean tides, there is a craggy shore with bright green algae growing on its eroded rocks where men fish in the distance. To the north, there are wide, flat sandy beaches but to the south, cliffs and caves are found on shoreline.

Beaches and dunes near Asilah and elsewhere have been a source of sand mining for construction in Morocco. In a 2007 paper co-written by Orrin H. Pilkey, Robert S. Young, Joseph Kelley, and Adam D. Griffith, they report that “Once beautiful coastal dunes have been entirely removed along long reaches of shoreline. This is a potential economic disaster for coastal tourism in Morocco.” (5)

” Once beautiful coastal dunes have been entirely removed along long reaches of shoreline. This is a potential economic disaster for coastal tourism in Morocco ”
— Pilkey, Young, Kelley, & Griffith

Tourism has become a vital part of Asilah’s ecomony like many cities in Morocco. The city underwent a 3-fold population increase in the decade following restoration. (3) Today, Mohammed Benaissa is the chairman of the council that approves municipal development. In a January meeting this year, a new 3-story modern marketplace and several projects including a crafts complex and bus station were approved. (6) Benaissa has been instrumental in preserving the integrity of their culture, keeping foreign interests out of the picture, and integrating locals throughout the process of rehabilitation. For example, there are no large scale hotels in Asilah. Aga Khan Development Network, in their 1989 report, warned that Asilah could be destroyed by tourism and building speculation if it is allowed to happen too rapidly. (3)

A “program to strengthen the drinking water supply in the cities of Tangier and Asilah as well as in towns and neighboring douars” was recently announced by L’Economiste, described as a “mega-project” and presented by “the Sovereign of the construction works for the dam Kharroub.” (7, 8) Clean potable water is not adequate throughout Morocco. This project will also increase water availability for industry, fueling development for this region. There is potential here, as with all rapid development, for negative consequences if not carefully regulated and controlled.

Over last year’s Easter holiday, a 5-day tourism conference was held in Asilah. organized by the Regional Tourism Council Tangier-Tetouan. The council states that “Asilah suffers from a lack of tourism infrastructure” and “the absence of a tourism promotion policy” (translated from French). In particular, they want an information kiosk and advertising budget. They emphasized establishing tours that capitalize on natural sites and historical and archaeological relics in areas outside of urban districts. (9)

The Jewish cemetery is a popular site of historic interest. Without guidance, I missed the landmark, which is deteriorating, located adjacent to the ocean, south of the city. (10) Conquered by the Portuguese in the 1471 (11) and fortified with a wall, the invasion of Asilah was captured in a tapestry that reveals the invasion and looting of the city. (12) Asilah became a refuge to Jews when they were expelled from Spain in 1492, then Portugal, along with the Moors, by royal decree in 1497. (13) The Jews were later aided by the Portuguese in their conflicts with the existing population. (14)

The Jewish cemetery reveals a time when many coastal cities became enclaves of immigration for Jews in the age of exploration, but perhaps is even older. Asilah was a Phoenician colony in the 16th century BC and “…Jews have lived in Morocco since the days of Nebuchadnezzar, when they escaped Babylonian captivity on Phoenician merchant ships” (15) This example shows the cultural mélange of Morocco, and how a site such as the Jewish cemetery can work to paint a picture of historical events that contribute to Asilah’s identity.

” I got a sense in Morocco often of the two-headed beast that is tourism..”
— Celie Dailey

To the traveler looking for an authentic experience, Asilah was a welcome change from the bombardment from vendors, for example, in the city of Marrakesh. The slower pace of life in Asilah I hope will remain as they bolster their economy.

Cultural identity is so easily mutated when it becomes a source of income. I got a sense in Morocco often of the two-headed beast that is tourism. As a visitor, the authentic experience is a mirage, because I’m looking for a Morocco void of the influence of me, the tourist. Funds brought by holidays abroad are substantial income which alter an economy greatly. Culture is not a thing of the past, but exists here and now, in a complex relationship among international constituents.

This is the Morocco I found, in a state of flux, seeking modernity. Asilah is an example of the kind of balance that can be achieved while accommodating tourism, preserving traditions, and welcoming contemporary art and culture.


BIBLIOGRAPHY

What the Sands Tell Us: a Look Back at Southeastern US Beaches; By Orrin H. Pilkey & William J. Neal

Figure-8

By Orrin H. Pilkey, Nicholas School of the Environment, Duke University, Durham, North Carolina, and William J. Neal, Department of Geology, Grand Valley State University, Allendale, Michigan;

In the 1960s, we were both working independently on sand studies: Pilkey with Bob Giles, his master’s student, and Neal, a master’s student with Dr. John Hubert. Giles and Pilkey carried out a regional study of the minerals in beach, dune and river sands of the Southeastern United States (1965) in a follow-up study to Pilkey’s work on the continental shelf and slope (1963).
In Neal’s study of Atlantic deep-sea sands, he summarized published data on heavy minerals for Atlantic Coast beach/dune and shelf sands (Hubert and Neal, 1967). Pilkey and Giles collected sand-sample sets at 53 beach/dune locations along the 400-mile stretch of shorelines between Cape Hatteras, NC and Miami Beach, FL, as well as 40 sand samples from the rivers flowing to these shores. The purpose of the study was to characterize, compare and contrast the sands of these environments regionally as well as locally, and to evaluate sources of these coastal sands. The relative contribution of specific minerals to the beaches is in part a function of where the source-rivers originate, either in the Piedmont or the Coastal Plain (Fig. 1).

” Typically, four common types of sand grains are recognized on beaches: light minerals, heavy minerals, carbonate sand derived mainly from shell fragments, and volcanic sands.”
— O.Pilkey & W.Neal

All beaches contain a variety of minerals, unique “suites”, which are like fingerprints in the sand—fingerprints that are clues as to where the sand came from (e.g., inland parent rock types, marine shells, offshore reefs), how far it was transported before it got to the beach, and by what means the sand was transported (e.g., rivers, wind, waves and longshore currents). The sand-sized mineral grains can also give us information on the processes that may alter the grains once they reach a beach.

Typically, four common types of sand grains are recognized on beaches: light minerals, heavy minerals, carbonate sand derived mainly from shell fragments, and volcanic sands (e.g., olivine, glass, sand-sized rock fragments). For our purposes along the beaches of the Southeastern U. S., only the first three of these major types of sand grains are important in dunes and beaches (i.e., volcanic sands are found in association with volcanic coasts like the Hawaiian Islands and are not important in the SE U. S.). Light and heavy minerals are defined by their specific gravity. Water has a specific gravity of 1.0. The light mineral quartz has a specific gravity of 2.7 (feldspars are in the same range), while heavy minerals are defined by specific gravities higher than 2.9. On most beaches, light minerals make up the bulk of the sand volume and, compositionally, quartz and feldspar grains are the most common type of light minerals.The latter reflects the fact that feldspars are the most common rock-forming minerals in the Earth’s crust, and quartz is a common mineral in continental granites and gneisses. Feldspars are less resistant to chemical weathering and mechanical abrasion than quartz, so with time and wear and tear, feldspar is lost from the sand fraction while resistant quartz persists. So quartz sand dominates many beaches in terms of their bulk mineral composition (Fig. 2).

The heavy-mineral fraction of sand in southeastern U.S. beaches is usually less than 5% of the total mineral composition, but the ‘heavies’ are often the most interesting as they are the ‘fingerprint minerals’. Because the heavy mineral fraction is often made up of dozens of different minerals, investigators find them most useful for answering many beach questions. The most common heavy minerals in beach sands, which give the black color to the heavy-mineral fraction, are the opaque minerals, commonly magnetite (iron oxide) and ilmenite (iron titanium oxide). Both have specific gravities above 5 (Fig. 3). Gold has a specific gravity of 19! The opaque minerals are responsible for the patches of black sand on beaches (sometimes mistaken for oil pollution)—concentrations of heavy minerals that are examples of natural placer deposits (Fig. 4). The heavy minerals are dispersed through the entire beach, but under the right conditions, placer deposits form. For example, when a wave washes up on the beach, all of the sand is carried forward, but the back wash has much less energy. So the heavy mineral grains are more likely to be left behind because of their higher specific gravity (especially those with the very high specific gravity), while the lighter quartz, feldspar, mica and shelly sands are carried back seaward. Commonly these placers are found on upper beaches, especially after storms. Various combinations of wind and water separate the heavy minerals from the light minerals or other heavy minerals and concentrate them in patches of colored sand, dependent on the dominant mineral (e.g., pink or purple garnets, green epidote) (Fig. 4) (see also Griggs, 2015). Such concentrates are sometimes seen in the wind-generated ripple marks on the back of the beach (Fig. 5), or where backwash creates crescent patterns around obstacles on the beach. Alternating layers or laminae of light-mineral sands and heavy-mineral sands also enhance the appearance of secondary structures in beaches such as ring structures (Fig. 6), and laminations as seen in cross section (Fig. 4).

The third sand type typical of these beaches is carbonate sand, derived from the abrasion and breakdown of marine shells and skeletal material. Coarser shell lags common to these beaches (Fig. 7) are indicative that a variety of clams, snails, and other carbonate skeletal fragments are constantly being broken and abraded into sand-sized particles.

Southeastern U. S. Beaches

Giles and Pilkey found that the most common light mineral in beach sands of the study area was quartz (90%), followed by feldspars and chert. Sand-sized shell material ranged in percentage from zero to 50%. But it was the heavy mineral fractions that yielded the most answers as to where the land-derived sands came from, and their alteration due to weathering and transport.

For the heavy minerals, only the fine sand fraction was examined, so as to avoid mineralogic differences due to grain size. The minerals examined in the study (separated from the light minerals by a heavy liquid) were the translucent rather than the opaque. Common translucent minerals in the study area included amphiboles (hornblende), sillimanite, zircon, rutile, staurolite, garnet, kyanite, epidote, tourmaline and others. The alert reader will recognize that most of these minerals would be valuable gemstones if only they were a bit larger than sand grains. (Fig. 8)

” Generally, today’s rivers are not contributing sand directly to East Coast beaches.”
— O.Pilkey & W.Neal

Although heavy minerals at the source of the river sands, far inland, are often more common than quartz, the relative abundance of the two changes as the grains are transported down rivers to the sea. Heavy minerals tend to break up during transport and are also susceptible to destructive chemical weathering. Different minerals break up and react chemically at different rates, which provide a basis to determine relative age differences of sands. Hornblende, actinolite, epidote, and garnet are relatively unstable minerals. Zircon, tourmaline, sillimanite and staurolite are relatively stable.

Conclusions from the Heavy Minerals:

  • The rivers that begin in the Piedmont Province carry a diverse mineral suite, but one dominated by relatively unstable minerals, while the shorter, smaller coastal plain rivers have higher percentages of stable minerals.
    In other words, Piedmont rivers usually have a greater abundance of amphiboles (mainly hornblende) and epidote, while Coastal Plain rivers show increases in zircon, sillimanite and staurolite. Other studies have noted similar trends (Windom et al., 1973). Piedmont rivers extend into the igneous and metamorphic rocks and thus start out with abundant heavy minerals, both stable and unstable. The sediment load of coastal plain rivers comes from previously deposited sediments. These grains may have resided in the coastal plain for thousands of years, during which time many of the unstable minerals were removed. In addition, it probably takes longer for sand in the smaller Coastal Plain rivers with gentle gradients to get to the beach, and thus there is more time for physical and chemical changes to alter the grains. Piedmont rivers, with much larger flow volumes, transport grains more efficiently, especially in major floods.
  • The heavy minerals of most beach sands (except for Florida) indicated Piedmont river sources for the sand, whereas the Coastal Plain rivers provide a relatively small proportion of beach sand, even though the Coastal Plain is immediately adjacent to the ocean shoreline.
  • Generally, today’s rivers are not contributing sand directly to beaches. Instead, the sand load of each river is deposited in the upper reaches of the estuaries, tens of miles inland. There is heavy mineral evidence that supports this conclusion. Mapping of the heavy mineral distribution of the continental shelf (Pilkey, 1963) indicated that the offshore mineralogy does not match the mineralogy of the river sand from adjacent rivers. If today’s rivers aren’t building up East Coast beaches, where did the sand on the beaches come from? We believe that today’s beaches were supplied with sand when the sea level was lower and the heads of estuaries were in the vicinity of the present day shoreline. On the steeper North American Pacific shoreline, rivers empty their loads directly into the sea at river mouths. One ramification of all this is that dams on Southeastern U. S. rivers will not likely impact the sand supply to beaches, but in California the damming of rivers traps sand and causes serious beach erosion due to the cut off of sand supply.
  • The southernmost source of Piedmont river sands along the Southeast U.S. shoreline is the Altamaha River in Georgia. As a result, the heavy minerals in Florida beach sands become progressively more stable (as unstable minerals are removed) going to the south along Florida’s east coast. For example, the average unstable garnet content of North Carolina beaches is more than 10%, while the average in Florida is 3%. And stable sillimanite in Florida beach sand averages a little over 20%, while in North Carolina the average is 12%. The shell content of Florida sand is much higher than that of the three states to the north. On average, the Florida beaches contain 23% shell fragments whereas North Carolina beaches contain 4%. Perhaps because of dilution by shell fragments, heavy minerals are much less common in Florida than in beaches to the north. Black sand patches on beaches are much less common in Florida.

” We now live in a time that some like to call the Anthropocene—a time when human activities are altering the Earth’s ecosystems to the point that the alterations are recognizable in the geologic record..”
— O.Pilkey & W.Neal

A 50-Year Perspective: Some Studies Can’t Be Duplicated

Since this discussion is based on papers from the 1960s one might think that it is outdated, but such is not the case. Prior to 1965, very few Southern U.S. beaches had been replenished, so the beach sands collected for these studies were largely natural and uncontaminated (no artificially added sand). At that time, instead of putting fresh sand on the beach, a more common way to respond to shoreline retreat was to build seawalls. Replenishment came to the fore when shorelines began threatening more and more houses and when it was discovered that seawalls destroy beaches. Today many beaches have been replenished multiple times using sands from several sources that may or may not be related to natural processes that bring sand to the beach.

For example, for years Virginia Beach, VA, trucked sand from miles inland to their beaches. The sand source was a 120,000-year-old shoreline deposit, from a time of higher sea level—sand which was weathered for all that time and had changes in its mineralogy, as discussed above. Myrtle Beach, SC, is not on a barrier island and as the shoreline erodes, it is contributing sand to the beach from the same previously deposited 120,000-year-old shoreline mined by Virginia Beach. Edisto Beach, SC, was replenished using very muddy and shelly sand obtained mainly from salt marshes behind the island. And replenishment projects for parts of the North Carolina shore have come from offshore ancient sand deposits which again have a different mineralogy than the original historic beaches.

We now live in a time that some like to call the Anthropocene—a time when human activities are altering the Earth’s ecosystems to the point that the alterations are recognizable in the geologic record. The fact that we can no longer do a beach/dune sediment study of the original natural conditions in many parts of the world because of the alteration of these environments is a reflection of this time. And if such studies have not been done in the past, then it is difficult to establish base lines against which to measure our impact on ecosystems.


References

Giles, R. T., and Pilkey, O. H., 1965, Atlantic Beach and Dune Sediments of the Southern United States: Journal of Sedimentary Petrology, v. 35, p. 900-910.

Griggs, G., 2015, The Colors of Beach Sands: Coastal Care Beach-of-the-Month, Feb. 2015:

Hubert, J. F., and Neal, W. J., 1967, Mineral Composition and Dispersal Patterns of Deep-Sea Sands in the Western North Atlantic Petrologic Province: Geological Society of America Bulletin, v. 78, p. 749-772.

Pilkey, O. H., 1963, Heavy Minerals of the U. S. South Atlantic Continental Shelf and Slope: Geological Society of America Bulletin, v. 74, p. 641 -648.

Windom, H. L., Neal, W. J., and Beck, K. C., 1971, Mineralogy of Sediments in Three Georgia Estuaries: Journal of Sedimentary Petrology, v. 41, no. 2, p. 497-504.

Balneário Dunas Altas, Southern Brazil; By Andrew Cooper

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By Pr. Andrew Cooper, School of Environmental Sciences, University of Ulster

A small beach community on the coast of Rio Grande do Sul province in Brazil, Dunas Altas comprises a set of holiday homes, occupied only in the summer. Nestled among the dunes, the remote town is deserted in the bleak and cold winter months, but in summer it is bustling with visitors.

The South Atlantic waters are brown here as a result of sediment discharge from the Rio de la Plata and the Lagoa dos Patos. Dunas Altas is near the northern end of a beach that runs unbroken for 300 km from Rio Grande to Tramandai.

The wide sandy beach is compact and hard – the strong winds blow any dry sand into the dunes – and consequently it is often used as a road by normal cars and motorcycles.

” It is common to find a few dead penguins washed up on the beach. Their corpses can form the nucleus of new dunes.”
— Andrew Cooper

A hazard to traffic, however, is posed by the numerous small channels that discharge across the beach. These are known locally as ‘sangradouros’ or washouts. They occur when rainfall elevates the water table and the excess water flows seawards across the beach in shallow channels. The margins of the channels are often zones of quicksand where even a footstep causes the sand to liquefy. These ephemeral channels, however, play an important ecological role for juvenile fish and organisms that live in the beach.

The waves on this part of the South Atlantic coast are large and energetic. A series of nearshore bars breaks their energy and creates an impressive wide surf zone. Dunas Altas takes its name from the dunes that are present all along the beach. Contrary to their name, they are not particularly high (most are less than 10 m high).

The dunes are migrating inland over the wet coastal plain and they are fed by sand blowing inland from the beach.

An unexpected sight here on the south Brazilian coast is to see penguins swimming in the surf. Carried on the north-flowing Falklands current they often find themselves out of their normal comfort zone and it is common to find a few dead penguins washed up on the beach. Their corpses act like any other detritus on the beach and they can form the nucleus of new dunes.

St. Ninian’s Tombolo, Shetland, Scotland; By Norma Longo

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By Norma Longo, Nicholas School of the Environment, Duke University, Durham, North Carolina

A headline from The Scotsman in August 2013 proclaimed “Shetland beach among best places in world to swim” and the news article following said “Despite its icy temperatures, a Shetland beach has been named among the best places in the world to swim, alongside those in the Caribbean, Australia and the Mediterranean.” This beach is St. Ninian’s Tombolo, a coastal feature that connects the southwest Shetland Mainland with St. Ninian’s Isle. The Isle’s name is a dedication to Shetland’s [unofficial] patron saint, Saint Ninian of Galloway, and the tombolo is known locally as an ayre, from the Old Norse Eyrr for ‘gravel bank.’ The village of Bigton on the Mainland is adjacent and offers good views of the tombolo.

Lying off the southwestern coast of the Shetland Mainland, the 500-meter-long tombolo is the largest geomorphologically active sand tombolo in Britain. The ayre most likely formed during a period of rising relative sea level, during the Holocene epoch (Hansom, 2003). Flinn (1997) noted that for 300 years, the shape and position of the tombolo had not changed much, despite the mining of large amounts of sand for local industry, or from being submerged by waves during storms. Hansom wrote that the active body of sand migrated to the north about 30 to 40 meters in the early 20th century and then migrated slowly back to the south. Currently, it shows seasonal changes, with loss of sand from the center and gain at the ends in winter, and with sand returning to the center in the summer.

The Atlantic Ocean location features plunging cliffs on both the Mainland and the Isle, with no adjacent beaches to supply sand to the tombolo, as is normally the case with tombolo formation. The beaches of the tombolo face to the north and to the south and are flanked by dunes and blown sand on either end. The dunes and sand deposits form the sink for most of the nearshore sediment circulation system here. The blown sand volume at the eastern [Mainland] end is normally larger than that on the western end, which was the area used in the 1970s as a site for commercial sand extraction. The mining pit has since been filled in by blown sand, and low dune mounds are present. Some erosion is present both to the east and the west. (Hansom, 2003)

” Lying off the southwestern coast of the Shetland Mainland, the 500-meter-long tombolo is the largest geomorphologically active sand tombolo in Britain.”
— Norma Longo

The Blue Flag beach, a natural sand causeway between the two land masses, is made up of medium-grained sand with about 50% carbonate content over a base of shingle or rock at two meters depth. It consists of two concave arcs due to being subjected to waves from two opposing directions: arcuate waves approach from St. Ninian’s Bay to the south and from Bigton Wick on the north side. The fetch is limited to no more than two kilometers, which restricts some wave activity. The curve of the approaching wave crests exactly matches the arc of the beaches on either side of the ayre (Hall & Fraser, 2004). Ocean swell approaches St. Ninian’s Isle from the west-southwest, and the waves are diffracted and refracted around the Isle to meet and break on the tombolo, bringing sand from the sea floor via the wave action (Flinn, 1997).

The beach height fluctuates, and at times, during spring high tides or storm events, the middle of the tombolo, which is typically about 20 – 30 meters wide at high tide, is completely submerged. In addition, storms occasionally breach the ayre and the water typically flows through the resulting channel from north to south. Hansom points out that in the 1993 Braer storm, the center of the tombolo was underwater for several days. The storm was named for the oil tanker by that name that ran aground on the 5th of January 1993 on the west side of Garth’s Ness, to the south of St. Ninian’s Isle. The Braer was carrying nearly 85,000 tons of light crude oil and about 1,600 tons of fuel oil, all of which leaked out as the ship broke up and sank over a period of 12 days. This was more than twice the amount of oil that the Exxon Valdez spilled in Alaska and is noted to be the 14th largest oil spill in the world (ITOPF, 2013; Harris, 1995). It caused the largest ever pollution incident in Scotland. Oiled debris and seaweed were washed ashore and had to be removed. Of the 39 beaches considered at risk, 20 were oiled, and cleanup operations, incorporating both mechanical and manual methods, were required at 9 sites. Surface oil pollution reached northward beyond St. Ninian’s tombolo, which was one of the polluted sites cleaned manually afterward. None of the oil from the wreck was salvaged, but due to the heavy storms and the lightness of the type of oil, the spill was dispersed rapidly. Even so, land contamination and air pollution affected public health, agriculture, seabirds and animals, fisheries, and fish farming industries. The long-term effects were not as severe as they were initially feared to be, although some fishing had to be abandoned for several years because of the traces of oil found in the fish and shellfish. Millions of farmed salmon had to be destroyed because of contamination, as the fish could not escape from their cages to go to clean water. (Harris, 1995; M/V Braer oil spill links)

Animals on St. Ninian’s Isle itself may not have been affected. A local farmer uses the grassy island for grazing his sheep that cross the tombolo for access to the Isle. An interpretive sign at the eastern end of the tombolo notes that St. Ninian’s Isle was inhabited until 1775, and since then it has been used as a sheep farm. The high cliffs and sand areas of the Isle provide homes for rabbits as well as a variety of birds. The Isle (and most probably, the tombolo) also has a long history of human activity. In this historically important area, the remains of a 12th century chapel were found on the eastern side of the island. An archeological dig at that site uncovered a treasure of 8th century silver items hidden beneath the chapel floor. Archeological digs have also found remains of a pre-Norse chapel which overlay an Iron Age site. Burial grounds were found at each level.

The tombolo and Isle comprise a Site of Special Scientific Interest (SSSI), designating a protected area in the U.K. The Scottish Natural Heritage (SNH) booklet (2011) provides this information: “SSSIs represent the best of Scotland’s natural heritage. They are ‘special’ for their plants, animals or habitats, their rocks or landforms, or a combination of these.” Further, “if you act without consent or intentionally or recklessly damage an SSSI’s natural feature(s), you may be committing a criminal offence, and if found guilty, fined. If you are convicted of damaging the natural feature(s) of an SSSI, by carrying out an activity without consent, a court may also make you repair the damage at your own expense.”

The tombolo beach was the winner in 2010 of the Keep Scotland Beautiful Seaside Award (STV, 2010), but in 2011 and 2012, a controversy developed when quad-bikes roaring up and down the beach and dunes created unwanted noise and caused disturbances to visitors and the ecosystem itself (Meyer, 2011). Some discussion was found in The Shetland Times. The tombolo was noted to have “large numbers of people on quad machines charging up and down the beautiful beach without a care for other visitors. . . leaving the acrid smell of distasteful burnt fuel that lodges in the throat. . . ” (Merrifield, 2011). Another writer said the machines sounded like giant mosquitoes and the noise went on all afternoon (Lawrence, 2011).

” St. Ninian’s Tombolo is a spectacular example of an active tombolo and is a beautiful beach for strolling, viewing wonderful scenery, and even swimming.”
— Norma Longo

The gist of the debate was that concerned people wanted the annoying and damaging machines banned from the beach. Opposing that view, one writer wrote: “What “fragility” exists at the site in question? The beach has been there for centuries without any protection from the very worst of anything and everything the Shetland climate and the western ocean could throw at it, anything that had any inherent “fragility” is already a very long time gone. I fail to imagine what a few motorbikes on an occasional weekend can possibly do to “destroy” something that has withstood lashing wind and rain, and driving sea for so long” (Garriock, 2011). The writer also mentioned that the bikers had been using the beach for decades. The controversy may not have been settled at the time of writing. The noise from the vehicles will likely continue to disrupt the typical quiet of the Shetland coast.The farmer drives his tractor across the tombolo to tend to his sheep on the Isle, but that wouldn’t create noisy disturbances equal to those from the quad bikes.

Meyer wrote [regarding SSSIs] in The Shetland Times that “Access rights conferred by the Land Reform (Scotland) Act 2003 do not extend to the use of motorised vehicles for recreational use – unless the landowner has granted strict individual permission.” The following statement from the SNH website (2011) seems to deem the loud activity acceptable: “[The tombolo] attracts recreational vehicles, especially scrambling bikes and quads. This does not damage the tombolo where the tracking is restricted to soft sand below the high water mark, as wind and tides soon restore the natural shape. Use of vehicles within the dunes however leads to erosion and is damaging to the structure of the site.” Studies have shown that driving on beaches does damage the ecosystem and change the shape of the beach and dunes. Animals, including the microscopic fauna that live in the sand, and plants are detrimentally affected (Cooper & McKenna, 2009; Schlacher & Thompson, 2007).

St. Ninian’s Tombolo is a spectacular example of an active tombolo and is a beautiful beach for strolling, viewing wonderful scenery, and even swimming. Dogs and children enjoy the area and can play safely (on days the quad bikers are not present). Sea level rise and land subsidence doubtless will play roles in the future of the ayre.


References Cited:

  • Cooper, J.A.G. and J. McKenna, 2009. Managing cars on beaches: A case study from Ireland. In: Williams, A. & A. Micallef, Beach Management. Principles and Practice. London: Earthscan Publishers.
  • Flinn, D., 1997. The Role of Wave Diffraction in the Formation of St. Ninian’s Ayre (Tombolo) in Shetland, Scotland. Journal of Coastal Research, Vol. 13, No. 1, pp. 202-208.
  • Garriock, M., 18 June 2011. Comment to Travesty at St. Ninian’s (Paul Meyer), The Shetland Times, Lerwick.
  • Hall, Adrian and Allen Fraser, August 2004, updated 2013. Shetland Landscapes [Edinburgh, Scotland].
  • Hansom, J.D., 2003. St. Ninian’s Tombolo (Coastal Geomorphology of Scotland). In May, V.J. and J.D. Hansom, Coastal Geomorphology of Great Britain, Geological Conservation Review, volume 28, chapter 8: Sand Spits and Tombolos. Joint Nature Conservation Committee, Peterborough, UK.
  • Harris, Chris, 1995. The Braer Incident: Shetland Islands, January 1993. In: Section VI, The Braer Incident, International Oil Spill Conference Proceedings,I Volume 1995, No. 1: pp. 813-819.
  • ITOPF: The International Tanker Owners Pollution Federation Limited, 2013. ITOPF Oil Tanker Spill Statistics 2013, and View
  • Lawrence, M., 7 June 2011. Spoiling the Attraction: Letter to the Editor, The Shetland Times, Lerwick.
  • Merrifield, J., 7 June 2011. Letter to the Editor, The Shetland Times,
  • Meyer, Paul, 13 June 2011 and 21 June 2011. Travesty at St. Ninian’s, Letter to the Editor (and comments), The Shetland Times,The Shetland Times, Lerwick.
  • MV Braer oil spill, retrieved 2/27/14 at View and, View
    and, View, and View
  • Pilkey, O.H., T.M. Rice, W.M Neal, 2004. How to Read a North Carolina Beach: Bubble Holes, Barking Sands, and Rippled Runnels. University of North Carolina Press, 162 pp.
  • Schlacher, T.A. and L.M.C. Thompson, 2007. Exposure of fauna to off-road vehicle (ORC) traffic on sandy beaches. Coastal Management 35: 567-583.
  • Scottish Natural Heritage, 2011. Sites of Special Scientific Interest. Battleby, Redgorton, Perth, 36 pp. (What owners and occupiers must do, p. 23) and View, and View
  • STV, 15 Sept. 2010. Shetland beach rates best in Scotland. Glasgow: Scottish Television.

Additional Reading:

  • Registers of Scotland, SSSI Register, 2007. St. Ninian’s Tombolo.
  • Ritchie, W., M. O’Sullivan, Ecological Steering Group on the Oil Spill in Shetland, 1994. The Environmental Impact of the Wreck of the Braer. Edinburgh: Scottish Office Environment Department, 207 p.
  • Smith, J., 1993. The Houb, Dales Voe: Coastal Processes. In Shetland Isles (J. Birnie, J. Gordon, K. Bennett and A. Hall, eds.), Quaternary Research Association Field Guide, Quaternary Research Association, p. 60.
  • Wells, P.G., J.N. Butler, J.S. Hughes, 1995. Exxon Valdez Oil Spill: Fate and Effects in Alaskan Waters. Philadelphia: ASTM, 955 p.

The Colors Of Beach Sand; By Gary Griggs

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By Gary Griggs, Distinguished Professor of Earth and Planetary Sciences, Director Institute of Marine Sciences, University of California, Santa Cruz, California

The words beach sand or beach probably conjures up a slightly different image for each of us. It might be the place where you spent summer vacations, the beach where you grew up, the beach on that travel poster of Tahiti that’s on your bucket list, or any of a number of other memorable experiences. And while many of our images of beach sand might be similar, beach sand can vary widely in size, shape and color.

The beach sand on the shoreline of the 30-mile long, crescent-shaped, Monterey Bay, California, where I’ve lived and studied beaches for 46 years, is downright plain throughout most of the year. The tan or buff color comes from a mixture of quartz and feldspar, durable minerals that have eroded from the sandstones and granite in the surrounding watersheds, carried to the shoreline by the rivers and creeks, and then worn, sorted, and rounded by wave action. It’s pretty typical looking stuff.

In the winter months, however, you can find black sand along some of Monterey Bay’s beaches. Because these dark minerals are heavier than the clear or lighter colored quartz and feldspar that make up the great bulk of most of the bay’s beach sands, the more energetic winter waves will wash the lighter minerals offshore and often concentrate these darker minerals into black sand beaches. The black or dark minerals, such as magnetite, ilmenite, and chromite, can be separated from the lighter colored sand by a hand magnet, like you used to do in the sand box as a child- well some of us who played in sand boxes did. These dark minerals contain heavy elements such as iron, magnesium, titanium, and chromium, and these denser grains are left behind by the large winter waves as they remove the less dense quartz and feldspar. The black sand will often be concentrated in small rills, channels, or in the troughs of the ripples on the beach surface.

The processes that concentrate these heavier minerals on beaches are similar to those that left gold behind in the streams of the Sierra foothills. Currents, whether in rivers or driven by waves or tidal fluctuations along the shoreline, will tend to sort out or separate the lighter from the heavier minerals. These concentrations of minerals are known as placer deposits and led to California’s Gold Rush. The beaches and shallow offshore waters of Australia are the source for about 95% of the world’s rutile, an important titanium mineral, as well as gold, zirconium, tin and chromium bearing minerals. Much of the world’s tin comes from similar sand deposits along the coasts of Malaysia, Indonesia and Thailand.

Twenty-five miles south of Monterey Bay at the mouth of the Big Sur River, a picturesque walk from Highway 1 through Andrew Molera State Park, you can find purple beach sand. The purple is from a very hard mineral, garnet, which weathers out of metamorphic rocks high in the adjacent Santa Lucia Range. Much of the sand paper you use is coated with garnet because it is a hard and abrasive mineral. Wind and waves have concentrated this purple mineral in interesting patterns along the beach for a considerable distance south of the river mouth.

“The color of any beach reflects the mineral composition of the sand grains.”
— Gary Griggs

Two hundred miles north of Monterey Bay, on the Mendocino Coast, lies the old lumber town of Fort Bragg. For decades the local residents used a beach at the north end of town as their city dump. In the days before recycling, anything that couldn’t be burned or fed to the chickens or pigs was dumped at some out of sight and convenient location. This was common in rural communities everywhere. Over the years the metal rusted away, but the glass was broken up and smoothed by the waves, leaving behind Glass Beach, which has become a popular tourist destination. Visitors spend hours on their hands and knees looking for their own treasures derived from Grandpa’s old beer bottles and Grandma’s old broken cups and saucers.

While an Oceanography graduate student at Oregon State University, I had the opportunity to spend a summer studying the coral reefs of Bermuda, about 600 miles off the Atlantic coast. Bermuda advertises its “pink coral sands” as an attraction to draw tourists. And they are pink, but it’s not coral that gives them this color. It’s actually a less familiar organism, a single cell animal known as a foraminifera, which makes a small pinkish shell. Although not particularly abundant, the small amount of pink in the otherwise white sand gives a distinct color to the beaches of Bermuda.

Three thousand miles west in the Hawaiian Islands, there are really only two things to make beach sand out of, either volcanic rock or coral and the shells of other tropical organisms. As a result, you either see gleaming white beaches or black sand beaches, often with concentrations of a green mineral, olivine, common in the basaltic lava that makes up Hawaii. At Hana, on the east coast of Maui, there are coarse-grained volcanic sand beaches, that contain both black grains of basalt, and also more weathered volcanic grains that are a rusty brown color.

The color of any beach reflects the mineral composition of the sand grains. Whether derived from the local bluffs or cliffs, the rivers and creeks that drain to the coast, or the organisms that may populate the near shore area, coral or coralline algae, mollusks, foraminifera or any of a number of other invertebrates that make hard skeletons or shells, it is these locally derived materials that make each beach a little different and somewhat unique.

My attraction to beach sand started when I began traveling to different coasts and noticed how many different colors of beach sand there were. So I started collecting small samples in 35mm film containers, which no longer are as common as they used to be. I then put these in glass vials and started putting them on bookshelves and windowsills. Over the past 50 years I have collected several hundred of these from all over the world. Nearly all of these bring back memories and, even while sitting in my office, they give me a sense of being back on the beach somewhere. Over the years, friends began sending me samples they had collected to add to my collection, from places I hadn’t been, Antarctica (which has beaches), Easter Island, Argentina, and Bora Bora, to name a few.

Not long ago I discovered that I wasn’t the only one who collected beach sand and that there was a name given to these collectors, arenophiles! The prefix “arena” such as is used to describe sandstones (“arenites”), actually came from the Romans who used to scatter sand around the arena to soak up the blood shed after their coliseum battles.

There is actually The International Sand Collectors Society with a newsletter called the Sand Paper. One of the most interesting beach sand collection sites is The World Atlas of Sands, which contains photographs of thousands of different beach sands that have been displayed in countless different sorts of glass containers by arenophiles worldwide. This site gives a whole new perspective to beach sand.

Dauphin Island, AL; By George Crozier and John Dindo

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By George Crozier and John Dindo

Dauphin Island is a “drumstick” shaped barrier island (16miles/26 km) on the western side of the main pass at Mobile Bay about 48 km (30 miles) south of Mobile, Alabama. The island is bounded to the northeast by Mobile Bay, to the north by Mississippi Sound and the Gulf of Mexico to the south. The eastern end is about 6.4 km (4 miles) long by 2.4 km (1.5 miles) wide sheltered by one of the largest ebb tidal deltas in the world. This remnant of the Pleistocene era rises from 1.5 – 3 meters (5-10 ft) to historic dune heights of what had been nearly 14 m (45 ft) above mean sea level.

“The relationship between the east end of the island and the ebb tidal delta, referred to as the “Sand Island/Pelican Island” complex, is extraordinarily dynamic and complex.”
— George Crozier & John Dindo

The Alabama National Guard routinely spent part of the summer pushing these massive dunes off of the three-room elementary school on the island. These massive dunes have gradually winnowed away so that there is only a remnant overlooking Pelican Bay.

The relationship between the east end of the island and the ebb tidal delta, referred to as the “Sand Island/Pelican Island” complex, is extraordinarily dynamic and complex. The ebb tidal delta may exist as one or two islands with the eastern-most referred to as Sand island and the western-most as Pelican Island – and at times there may be several ephemeral islands making up this unusual offshore barrier.

The 18 km (11 mile) Holocene barrier spit to the west has an elevation of no more than 2 m (6-7 feet) and is only 200 m – 350m wide throughout much of its length. This is the area routinely impacted by storm surge and the criticisms by various media rarely recognize the drastically different ends. The opposite ends of the island are indeed very different because the east end is of substantially higher elevation and heavily wooded maritime forest backed by coastal salt marsh. The problems that are attributed to Dauphin Island are most evident on the heavily developed “the west end” of the island – a strip only about 3-4 miles long where most of the insured loss and infrastructure destruction occurs.

The relative security of the east end of the island made it an attractive place for development in the early years of the last century. There wa s even a proposed “world port and coaling station” described for the northeast side of the island in 1920. It was further noted in this chamber of commerce flyer that the island had never been damaged by storm even though Mobile was hit by two major hurricanes in 1916.

The first bridge was built in 1955 and with vehicular access provided, development was inevitable. The ownership of the island was vested in a Property Owners Association (POA) and the island was subdivided in a typical mid-20th century grid providing about 3,000 individual lots. The POA developed covenants that essentially zoned the island and it kept the beach of the “west end” as a common holding of the association.

The normal pattern of storm impact has been the predictable overtopping of the low barrier with formation of dramatic overwash fans into Mississippi Sound. This event is promptly followed by appeals from the Town of Dauphin Island for relief from county, State and federal authorities. This usually involves a variety of processes moving sand from the overwash fans and returning it to the property owned by the POA or individual owners or as protective piles of sand. Fig. 3 by USGS demonstrates erosion by red and green is accretion. The red dots are (or were) houses.

Simultaneously the private owners filed for coverage under the National Flood Insurance Program (NFIP). The waterfront properties, some on Mississippi Sound to the north and most on the Gulf of Mexico to the south constitute less than 0.02% of Alabama’s land area but it has received 20% of the National Flood Insurance Program funding provided to the State over the years.

“Hurricane Katrina cut an inlet in the historically common location just west of the developed portion of the west end and effectively cut the island in half.”
— George Crozier & John Dindo

These protective barriers have never survived subsequent high energy exposure, leading to the ridiculous image below of “a day at the beach”.

The town’s budget depends to a large extent on the lodging revenues derived from the overwhelming number of west end properties. The request for aid in rebuilding these largely absentee landlord properties is understandable but there is very little public access provided so the result appears to be a massive subsidizing of private property within an essentially gated community.

Hurricane Katrina cut an inlet in the historically common location just west of the developed portion of the west end and effectively cut the island in half. No State or federal aid was available for restoring this area but a new “benefactor” emerged in the form of BP in the wake of the disastrous oil spill. Island interests argued that an “island made whole” was necessary for protecting the mainland communities and a rock wall was constructed under a one-year construction permit from the Corps of Engineers The oil spill impacts had virtually disappeared before the wall was completed. The project has been viewed locally as both maintenance of the storm barrier function as well as necessary for keeping appropriate salinities over oyster reefs in Mississippi Sound.

The town seized on the opportunity to acquire the ¾ of a mile west of the houses and began developing a beach that addressed the lack of public access AND generated some revenue by charging for parking and access to the new “public” beach.

Downdrift erosion of this area has been documented over and over again. In fact the most waterfront private lot immediately adjacent to the park is in fact now a “water -under” lot. Meanwhile the existing waterfront owners have recognized the erosional rate and have constructed seawalls which have been euphemistically recognized by the State as “sand retention systems”. Seawalls on the Gulf beaches are prohibited by regulations under the State’s Coastal Area Plan – apparently sand retention systems are not! Fig. 8-11.These pictures were taken late spring and the summer of 2013 by John Dindo.

The town and state authorities are so intimidated by the threat of a “takings” ruling that they have allowed this pattern of development to seriously jeopardize the $3 million investment in the public beach. Having opened the “floodgates”, other property owners have installed sand retention systems to protect their property also, Figures 10-11. Figure 10 also shows the current sand pile designed to protect the town’s infrastructure, the most recent FEMA –paid construction. This is supposed to protect the roads,water and sewer, as well as the power poles.

“Seawalls on the Gulf beaches are prohibited by regulations under the State’s Coastal Area Plan – apparently sand retention systems are not!”
— George Crozier & John Dindo

The town of Dauphin Island and the Property Owners Association are trying to obtain $30-70 million from the State’s portion of the RESTORE Act (BP oil spill settlement) arguing that the island provides significant protection to the mainland and preserves appropriate salinities for the fisheries using Mississippi Sound. It is argued that New Jersey received $1Billion from Hurricane Sandy but according to Wikipedia “Over two million households in the state lost power in the storm, 346,000 homes were damaged or destroyed,[2] and 37 people were killed. Storm surge and flooding affected a large swath of the state” – not a good comparison!

There are ongoing negotiations with the Corps of Engineers to construct and maintain some kind of sand bypass system at the mouth of Mobile Bay which would nourish the entire island from east to west but other than that there are no commitments for any more relief when that sand disappears. Oh well, there will probably be another hurricane with all its subsequent relief!

Beaches of Sleeping Bear Dunes National Lakeshore, Michigan; By William J. Neal & Gregory C. Wilson

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By William J. Neal & Gregory C. Wilson, Department of Geology, Grand Valley State University

Long featured in travel magazine articles, Sleeping Bear National Lakeshore has come to the forefront since being named ABC Television’s Good Morning America’s “Most Beautiful Place in America” in 2011, and listed as #1 among Dr. Beach’s “Best Great Lakes Beaches” the same year. In 2012 National Geographic included Sleeping Bear on its “10 Best Summer Trips” list. Sleeping Bear’s recognition as one of Nature’s masterpieces of the work of glaciers, lakes, wind and water, led to its 71,000 acres being given National Lakeshore status in the National Park System in 1970 (refs. 1, 2).

“Sleeping Bear’s recognition as one of Nature’s masterpieces of the work of glaciers, lakes, wind and water, led to its 71,000 acres being given National Lakeshore status .”
— William J. Neal & Gregory C. Wilson

Just as significant was the designation of over 32,000 acres of that area as ‘Wilderness’ in the National Wilderness Preservation System in 2014. The region’s topography is the product of more recent geologic history, particularly from the Pleistocene or great ice age to the last melting of North America’s continental glaciers, and the post-glacial history of the ancestral Great Lakes (refs. 3, 4). That complex history of events resulted in today’s fantastic scenery and the four seasons’ attractions of the region. While the inland area is of great interest, the focus here is on the beaches and associated modern dunes.

Sleeping Bear National Lakeshore has a 35-mile mainland shoreline, plus approximately 30 more miles of coast on North and South Manitou Islands. Artifacts tell us that the area has been an attraction to humans since the stabilization of lake levels around 3000 years ago. Europeans first visited these shores in the 17th century when French traders plied the lakes, followed by the English in early 1800s. One of the earliest recorded dune climbs was by the fur trader Gurdon Hubbard who climbed Sleeping Bear with a companion and then hop-skipped-jumped back down the slope (mimicked today at the Park’s dune climb by the thousands). But the area attracted only light settlement.

In 1884 G. K. Gilbert, a pioneer geologist, authored “The Topographic Features of Lakeshores”(p. 69 -123 in the Annual Report of the Director, U. S. Geological Survey) based mainly on his studies of shorelines in the Great Lakes and the Great Salt Lake. His Plate XIV (Figure 1) reproduced a map showing much of what is now the SBNL area, although not all of the shoreline. Note that only one village, Glen Arbor, was shown in the area. The shoreline topography consisted then, as today, of high-dune headlands, separated by lower topographic areas characterized by embayments. The embayment shores are consistently where the best beach/dune systems formed.

From south to north these four beach areas are:

  • 1. Platte Bay Beach extends from Platte River Point at the south end of the bay to the Empire Bluffs. This beach is one of the two larger beaches in the Park, running the length of the Platte Bay shore. An active dune field has grown at the mouth of the Platte River to form Platte River Point, and the beach is a sandy gravel becoming increasingly sandy to the north (Figure 2). The beach in the mid-bay area is wide, with a grassy dune field extending back to the forest (Figure 3). During the summer months, small nearshore sandbars migrate onshore and weld onto the beach, causing it to widen. The same sand will be carried offshore again in Fall storms. The beach face is constantly being sculpted by waves and breaking-wave swash which forms a variety of patterns, and often concentrates thin layers of heavy minerals (Figure 4). Bring a magnet to the beach and you will be able to separate magnetite from the other high-density minerals.
    Otter Creek is popular spot on Platte Bay Beach, particularly with bathers when the lake water is considerably colder than the sun-warmed shallows of the creek (Figure 5). This locale is a good observation point to see the interplay between the beach, creek mouth, and waves. The floor of the creek is covered with various patterns of current ripple marks, in contrast to the wave ripple marks on the sandy bottom of the lake. Platte Bay Beach narrows to the north as it approaches Empire Bluffs.
  • 2.The Empire Bluffs form a headland boundary between Platte Bay Beach and the more northerly Empire Beach which extends along a lowland until it again narrows as it approaches Sleeping Bear Dune (Figure 6). Although now not a pronounced bay, at one time Lake Michigan extended farther inland, but was cut off by a spit or emergent sand bar that eventually extended across the bay and cut off the body of water to form South and North Bar Lakes. Plate VIII of Gilbert’s 1884 study illustrates the bar/spit that formed off the headland to the north and cut off South Bar Lake from Lake Michigan (Figure 7). Part of the town of Empire is now located on that forested sand ridge, and a younger beach/dune has accreted lake-ward. The beach is widest at the village of Empire (Figure 8), in front of South Bar Lake, and continues to the North Bar Lake area before narrowing in front of the massive Sleeping Bear Dunes (Figure 6). These high dunes are ancient in the sense that they formed thousands of years ago, although they are still evolving. Part of their spectacular elevation is due to their “perched” origin (Figure 9). These dunes are sitting atop older glacial, lacustrine, and fluvial deposits. The northern end of this ancient perched-dune field forms Sleeping Bear Point, and there is a narrow beach fronting the steep dune face.
  • 3.Sleeping Bear Bay is another pronounced embayment, yoked by the westerly Sleeping Bear Point and Pyramid Point, another headland of eroding sands to the east/northeast (Figure 1). The beach here is best developed from the old Coast Guard Station (Figure 10) and Glen Haven Historic Village to the area north of Glen Arbor and the mouth of the Crystal River. Active dunes line the back-beach area.
  • 4.Good Harbor Bay Beach rivals Platte Bay Beach by its size and beauty. The beach/dune system extends eastward from the Point Pyramid headland to Carp River Point, just south of Leland. The beach is widest in the inner-most part of the bay, like the Platte Bay Beach, beginning at about the mouth of Shalda Creek on the west end and narrowing where the shore trends back to the north. The beach shows a variety of interesting beach features including bar attachment similar to the other bay beaches (Figure 11). At times, higher energy waves generate placers of fine heavy-mineral rich, dark sands.
  • “These beaches and dunes are dynamic landforms, characterized by natural processes that are hazardous from the human point-of-view.”
    — William J. Neal & Gregory C. Wilson

    Good Harbor Bay is clearly the remnant of a once greater embayment that extended south into the area that is now Little Traverse and Lime Lakes. With time and as lake levels fell, a series of spits and beach/dune ridges formed, separating these lakes and forming a distinct topography of low ridges and swales, although difficult to recognize under the forest cover. The present shoreline provides a good view of modern dune evolution, and an example of how the earlier ridges formed (Figure 12). The sands making up today’s dunes and beaches have been recycled many times – perhaps having come from Canada as glacial sediment, carried by melt waters from those glaciers, and those deposits eroded by ancestral lakes, carried by waters and wind in bars, beaches, and dunes, over and over. Like most Lake Michigan beaches and associated dunes, the sands of these two features at Good Harbor Bay Beach are the same composition, and differ only slightly in grain size (Figure 13).

    These beaches and dunes are dynamic landforms, characterized by natural processes that are hazardous from the human point-of-view. These shorelines have been and continue to be eroded. Calm sunny days of summer have led many to settle on the shores of the Great Lakes without knowledge of the terrible storms that lash the coast, or that fluctuating lake levels are like the tidal range of oceans, extending the zone of hazardous conditions landward. Landslides, slumps and creep create hazards even from gravity. And dunes migrate, burying forest and threatening property. Sleeping Bear is no exception. The first safety precaution at the shore is to heed the rip-current warning signs. In addition, steep slopes have an attraction, but losing your footing can have serious consequences. And yes, landslides do occur in the dunes. In 1995 a large landslide occurred at Sleeping Bear Point, depositing approximately 1 million cubic meters of sediment on the adjacent lake floor, extending more than 2 miles offshore! Similar slides occurred in the same area in 1914 and 1971 (refs. 5, 6). Even in undeveloped park and wilderness lands, shoreline change must be accounted for in planning, and the USGS has assessed all of the Great Lakes National Lakeshores for coastal change potential (ref. 7).


    References

  • 1. The Official Website Of Sleeping Bear Dunes:Provides general visitor information on Sleeping Bear Dunes and the area including maps, events, and activities.
  • 2.The Park Service’s official web site for Sleeping Bear Dunes: provides background information on the park and visitor information for planning a visit to the area.
  • 3.National Park Service, Explore Nature : “geology fieldnotes: Sleeping Bear Dunes National Lakeshore Michigan” 14p. This on-line reference provides a good discussion of the glacial/post-glacial history of the region, the origins of the array of land forms in the Park, and an extensive list of references for those interested in the geology of the region.
  • 4.Geological Society of America Centennial Field Guide— North-Central Section, 1987: Milstein, R. L., 1987, Sleeping Bear Dunes National Lakeshore, Michigan: Geol. Soc. America Centennial Field Guide – North-Central Section, 3p. Nice brief summary of the region’s geologic history.
  • 5. Barnhardt, W.A., Jaffe, B.E., Kayen, R.E., and Cochrane, G.R., 2004, Influence of near-surface stratigraphy on coastal landslides at Sleeping Bear Dunes National Lakeshore, Lake Michighan. Journal of Coastal Research, v. 20, p. 510-512.
  • 6.USGS Fact Sheet 020-98 Online Version 1.0.Jaffe, B., Kayen, R., Gibbons, H., Hendley II, J.W., and Stauffer, P.H., 1998, Popular Beach Disappears Underwater in Huge Coastal Landslide – Sleeping Bear Dunes, Michigan.
  • 7. Pendleton, E.A., Thieler, E.R., and Williams, S. J., 2005, Coastal Change-Potential Assessment of Sleeping Bear Dunes, Indiana Dunes, and Apostle Islands National Lakeshores to Lake-Level Changes: U. S. Geological Survey 2005-1249, 48p.