Tag Archives: Beach of the Month

Glacial Outwash Plain Shoreline, South-Central Iceland; By Albert C. Hine, Jon C. Boothroyd & Dag Nummedal

bom-584-07-2013

By Albert C. Hine, College of Marine Science – University of South Florida; Jon C. Boothroyd, Department of Geology – University of Rhode Island; and Dag Nummedal, Director – Colorado Energy Research Institute

Iceland is an island hot-spot built up by abnormally high volcanic activity on the North Atlantic mid-ocean ridge probably resulting from a mantle plume that detached from the Earth’s outer core/mantle boundary millions of years ago. Two mid-Cenozoic basaltic volcanic zones (upper ocean crust) are separated by a neo-volcanic spreading center offset by a transform fault system. This neo-volcanic zone (subaerial portion of the mid-ocean ride) supports frequently occurring volcanic eruptions.

During the Pleistocene glacial events, most of Iceland was covered with a single, large ice sheet. During the modern interglacial period, bedrock is mostly exposed except for a number of small ice sheets, and the 150 km wide Vatnajokull ice sheet (“jokull” is Icelandic for glacier), which covers the active spreading center and the Grimsvotn Volcano as well as other volcanoes and hot springs. The Vatnajokull is one the Earth’s remaining ice sheets left over from the Last Glacial Maximum coming in a distant third in size as compared to Antarctic (1st) and Greenland (2nd). Iceland has experienced isostatic uplift as a result of late Pleistocene ice sheet loss.

The 75 km long south-central coast of Iceland (Figs. 1, 2; See photo gallery above), anchored to the east by a basaltic rock headland (Ingolshofdi) and a point arbitrarily chosen to the west marked by the Skaftaros Lighthouse fronts a broad glacial, alluvial outwash plain, called a “sandur” (Icelandic for glacial outwash plain). This is a fan delta dominated by braided streams emanating from a large 25 km wide piedmont glacier—the Skeidararjokull.

Glacial Bursts or Jokulhaups

The 75 km wide and 100 m thick Seidararsandur formed from meltwater from the Skeidararjokull over the past 11 ky. The meltwater has been derived from three sources (1) normal summer runoff, (2) glaciogenic “jokulhaups” (Icelandic for glacial bursts—short term, but very large water discharge floods) from rapidly discharging ice-margin glacial lakes, and (3) volcanogenic jokulhaups from sub-ice volcanic activity beneath the Vatnajokull.

“… sediment input is catastrophic allowing the coastline to prograde as much as 4 km in a matter of weeks when these events occur. ”
— Hine, Boothroyd and Nummedal

The largest jokulhaups cause glacial streams having water discharges of ~400 m3/sec to increase to ~100,000 m3/sec, but lasting only for a few days or weeks. For a comparison the average discharge of the Amazon River is 170,000 m3/sec. The jokulhaups associated with the Skeidararjokull are normally in the 40,000-50,000 m3/sec. The jokulhaups (probable the glaciogeneic type) are becoming more frequent as the Skeidararjokull ice margin retreats (~20 m/yr) due to global warming (Fig. 3).

The sediments produced and released are mostly black obsidian and basaltic gravel and sand-sized fragments. The upper fan is dominated by gravel and the lower fan and coastal system consists of medium sand with median grain sizes ranging from 0.4 to 1.0 mm. The sediment discharge to the coast by each glacial burst (31 glacial bursts from the year 1389 to 1971) equals the sediment discharge 70-80 years of one year’s normal summer meltwater. So, sediment input is catastrophic allowing the coastline to prograde as much as 4 km in a matter of weeks when these events occur.

Wave and Tidal Energy Environment

Iceland is located between the Arctic and Polar Fronts which generate huge and powerful winter extratropical cyclones —the waves from which particularly impact the south facing coastline. Dominant wave power (13.75 x 1010 ergs /m/s) for December 1972 (December most extratropical cyclones/yr) was from the SE thus setting up a westerly longshore transport along the Skeidararsandur coastline. For the time frame Nov-Feb 1972, there were 62 storms having wind strength >Beaufort scale 10 (55-63 mph or 24.5-28.4 m/s). The wave power from the SW is an order of magnitude smaller. Wave hindcasting techniques have calculated significant wave heights of 14 m. Nearby wave gauges have measured wave height of 11 meters during these extratropical events. The spring tidal range is 2 m thus making this coastline to be classified as mesotidal even though it lacks many of the classic mesotidal geomorphic features found on sedimentary coastlines—the wave power and sediment input from the glaciers overwhelm the tidal range influence. The 4 km rapid coastal progradation mentioned above due to large jokulhaups erodes back quickly by this large wave energy flux to create a more stable coastline examined over longer time scales.

Coastal Morphology

This highly dynamical coastal system involving very high sediment input during the summer and particularly the frequent jokulhaup events and the enormous high wave energy events in the winter have maintained a relatively stable shoreline that has prograded only 1.1 km during the past 300 years. At the eastern basaltic bedrock anchor Ingolfshofdi, the shore has been mostly invariant (Fig. 4). Down towards the Skaftaros Lighthouse 75 km to the west, the coastline has prograded 3 km in 300 years due to the net westerly longshore transport. The high wave energy has created an extremely deep and steep shoreface that extends to 75 m deep closure depth ~4 km offshore having a gradient of 1:38. This shoreface supports a series of inshore bars having 5 m relief and crest in 7 m water depth. Beyond the shoreface, the inner shelf gradient decreases to about 1:170. In comparison, typical shorefaces off the eastern US have slopes of 1:200 decreasing to inner shelf gradients of ~1:2000.

Coastal Depositional Models

This 75 km coastline presents two different depositional models: (1) barrier spits backed by active braided streams, and (2) barrier spits backed by wind-tidal flats (Figs 5, 6). Barrier spits are elevated berms capped by eolian dunes. The eolian facies is dominated by unvegetated, transverse wind driven bedforms (transverse dunes). These wind-blown bedforms features active slipfaces when winds blow >20 kts persistently from generally east in summer for several days (Fig. 7). The bedform spacings range from 10-80m and height ranges from 0.1 to 2 m. These bedforms, built on top of the storm berm lack plants due to constant wind transport and the severe storm urge overwash—particularly in the winter. These eolian bedforms merge into fluvial bedforms along the backside of the barrier spit.

“This highly dynamical coastal system involving very high sediment input during the summer and particularly the frequent jokulhaup events and the enormous high wave energy events in the winter have maintained a relatively stable shoreline… ”
— Hine, Boothroyd and Nummedal

The barrier spits are backed by (1) elevated braided streams or (2) wind-tidal flats preventing the back barrier spits from being flooded by seawater—there are no marine lagoons along the Skeidararsandur barrier spit coastline. Glacial meltwater from the braided streams reach the elevated barrier spits, flow laterally along their backside until a river distributary (Fig. 8), is cut through the barrier spit. The lack of accommodation space for tidal lagoons was due to braided stream and wind-tidal flat aggradation and perhaps due to isostatic rebound as noted earlier. At the river distributaries, the meltwater is confined in narrow channels and flows directly to the North Atlantic Ocean. Regardless of tidal stage, flow seaward is not reversed but the seaward-directed flow velocity is reduced during high tides (~250 cm/sec at low tide reduced to ~60 cm/sec at high tide). Sediment discharge through the river distributaries under normal summer meltwater conditions also changes tidally—3.7 g/l at low tide—high seaward flow to 1.1 g/l at high tide–lower seaward flow. Occasionally, the entering, heavily sediment laden, glacial meltwater is hyperpycnal, particularly during the jokulhaups, such that that density underflows on the inner shelf are developed. The length of the barrier spits is defined by the presence of these river distributaries. Extensive fragmentation of the barrier spits occurs during glacial burst events (Fig. 3).

Barrier spits backed by braided streams (Fig.9A )

1. Located along the eastern part of the 75 km long Skeidararsandur barrier spit coastline (Fig. 1).
2. Underlain by fluvial facies formed by lateral migration of more common river distributary channels. River distributaries form 1-2 m high scarps as distributary migrates laterally (Fig. 10). Braided stream activity more common along the eastern Skeidararsandur than western portion in 1972 when the study was conducted.
3. Berm top and beach face stratification overlies fluvial facies due to frequent overwash during storms and during spring high tides (Fig. 11A, B). Intertidal swash bars and berm ridges common forming landward dipping cross-stratification.
4. Eolian bedforms (unvegetated transverse dunes) cap berm top overwash-generated plane laminations.
5. The fluvial, berm, and eolian succession forms to elevated topography that defines the barrier spit. Behind the spit braided streams commonly flow laterally until the breach or distributary in barrier spit is located. Eolian transverse dunes merge laterally landward into braided stream bedforms and linguoid bars.

Barrier spits backed by wind-tidal flats (Fig. 9B)

1. Located along the western portion of the Skeidararsandur barrier spit coastline.
2. Wider and higher due to absence of migrating river distributaries and lower frequency of jokulhaups.
3. Underlain by fluvial facies.
4. Also well-developed berm capped by eolian transverse dunes.
5. Back portion of spits grade into broad wind tidal flats, not braided streams, which become flooded during elevated wind events.

Differences between Icelandic barrier spits and barrier islands

1. Icelandic spits are underlain by fluvial not overwash, migrating tidal inlet, back barrier or lagoonal facies as are barrier islands.
2. Icelandic spits have no well-vegetated foredune ridge, maritime forest, or back barrier marsh.
3. Icelandic spits if not destroyed would be buried by jokulhaup flood deposits from behind.
4. Mulitple berm growth (aggradational and progradational ) seems much more prevalent along Icelandic spits than many barrier islands.


References

Hine, A.C., and Boothroyd, J.C., 1978, Morphology, processes, and recent sedimentary history of a glacial-outwash plain shoreline, southern Iceland: Journal of Sedimentary Petrology, v. 48, no. 3. P. 901-920.

Nummedal, D., Hine, A.C., Ward, L.G., Hayes, M.O., Boothroyd, J.C., Stephen, M. F., and Hubbard, D.K., 1974, Recent migrations of the Skeidararsandur shoreline, southeast Iceland:Final Report for Contract No. N60921-73-C-0258; Naval Ordnance Laboratory, Panama City, FL.

Nummedal, D., Hine, A.C., and Boothroyd, J.C., 1987, Holocene evolution of the south-central coast of Iceland, in, Fitzgerald, D.M., and Rosen, P.R., (eds.), Glaciated Coasts: New York, Academic Press, p. 115-150.

An Ancient Beach With Modern Subway Cars- 16 Fathoms Down To Take This Train; By Art Trembanis, Nicole Raineault & Carter DuVal

By Art Trembanis, Nicole Raineault, and Carter DuVal

It used to require a ticket to ride the Redbird line of subway cars but now you’ll need a set of SCUBA gear to ride these trains. Over 900 New York City subway cars sit on the seafloor, just 16.5 nautical miles (19 mi) from the Delaware shore (Figure 1 – map; See Gallery Above).

These subway cars are part of an artificial reef, known as the Redbird reef (after the line of subway car) that have been placed on the seafloor since 2001 (Figure 2). The Redbird artificial reef was established in 1996 when the State of Delaware started putting military track vehicles, ballasted tire units, and retired vessels including tugboats and trawlers in a 1.3 nautical mile area (1100 acres) on Delaware’s continental shelf. The reef, located at 28 m (92 ft) water depth, attracts fish, recreational fishers, and sport divers. The reef objects become completely encrusted in organisms and resembles the vibrantly colored reefs found in tropical climates (Figure 3).

This beach of the month is not a beach at all, at least it hasn’t been the beach for several thousand years. Geologists are interested in this artificial reef because of the story it tells about the shifting sand in the area.

This area is known as the Cape May retreat massif with a series of ridges and swales that mark the location of former offshore features (Figure 1) and was at a time of lower sea level perhaps as recently as 6-7 thousand years ago the location of ancestral Cape May.

In fact, sediment samples that we have recovered from the seabed on the top of the ridge exhibit the texture (size) and color of present day beach sands including the tell tale iron oxide staining (rust color) typical of subaerial exposed beach sands (Figure 3 upper left).

“Geologists are interested in this artificial reef because of the story it tells about the shifting sand in the area.”
—Art Trembanis, Nicole Raineault, and Carter DuVal

Meanwhile a sample taken at the base of the swale shows a much different picture and exhibits traits of having come from a less oxygenated environment with darker and coarser sediments consistent with the location of a former tributary of the Delaware River (Figure 3 upper right).

Using autonomous underwater robots to take images of the seafloor (Figure 4), scientists can tell that periodic nor’easters that affect the coast from November through March. The storm waves form a coarse gravel, cobble, and pebble moat around subway cars by removing the fine sand and mud near the reef objects. The moat can be several meters (10’s of feet) wide around object, but a shallower comet-shaped halo of gravel and coarse sand can extend ten’s of meters (nearly 100 feet). Not only is sediment moving, but the subway cars are settling deeper into the sea floor over time (Figures 5 and 6). Over 6-7 years cars sunk over 1 m (3 feet). More detailed examination of the reef conditions through time can be found in a recent article by Raineault et al., 2013.

The organisms that live on the pebbly and cobbly sea floor in the scour moat are different from the organisms living on the fine sand and mud. We found more sea stars, hermit crab, and clams near the reef objects. The subway cars were entirely encrusted in cold-water coral, anemone, sea stars, and bryozoans. Diver photographs show some large fish swimming through the windows and doors of the subway cars (Figure 3).

The ongoing research at the Redbird reef site can help inform decisions about infrastructure construction, including the wind towers currently planned for an area just north of this artificial reef. We are now using recently developed computer algorithms (Skarke and Trembanis, 2011) designed to study fingerprints similar to what the FBI uses but instead we are using them to study sand ripples on the seabed. Using the data we collect planners can minimize changes to the sea floor by accounting for the local geology and wave and current conditions when designing wind tower sites. Evidence from the mapping surveys conducted immediately before and after hurricane Sandy indicate significant scour of the seabed in the vicinity of the subway cars and several cars show clear signs of having been moved slightly or destroyed by the storm conditions (Figures 5 and 6).


Acknowledgements.
Funding of this project was made possible by a grant from the Office of Naval Research (Award Number: N000014121030). Thanks go to Dr. Larry Mayer (Co-PI), Dr. Jonathan Beaudoin (Co-PI), Dr. Doug Miller, Dr. Nicole Raineault, Dr. Adam Skarke, Val Schmidt, Justin Walker, Trevor Metz, and the captain and crew of the R/V Hugh R. Sharp


References:

NJScuba: Scuba Diving – New Jersey & Long Island New York
Raineault, N.A., A.C. Trembanis, and D. Miller. 2012. Mapping benthic habitats in Delaware Bay and the coastal Atlantic: acoustic techniques provide greater coverage and high resolution in complex shallow water environments. Estuaries and Coast,. 35: 682-699. DOI 10.1007/s12237-011-9457-8.

Raineault, N.A., A.C. Trembanis, D.C. Miller, and V. Capone, 2013. Interannual changes in seafloor surficial geology at an artificial reef site on the inner continental shelf, Continental Shelf Research, 58:67-78. DOI: 10.1016/j.csr.2013.03.008.

Skarke, A., and A.C. Trembanis, 2011. Parameterization of bedform morphology and defect density with fingerprint analysis techniques. Continental Shelf Research, 31: 1688-1700.

Gloucester Point Beach, Virginia; By Carl Hobbs

By Carl Hobbs, Virginia Institute of Marine Science, College of William & Mary

Gloucester Point Beach, Virginia, is a small, community beach on the north shore of the York River estuary a few kilometers upstream from Chesapeake Bay. The beach is on the downstream (east) side of Gloucester Point where, along with an adjacent public boat ramp and parking, it is otherwise surrounded by the campus of the Virginia Institute of Marine Science. The beach extends almost 250 m (800 ft) between a stone revetment that with a series of small breakwaters protect the VIMS campus and the groin-like short wall associated with the a boat ramp at the very tip Gloucester Point. It is exposed to wind and waves from the east and southeast with a fetch to the southeast of about 5 km (3 mi) and to the east of tens of km. Mean tidal range is about 0.75 m (2.4 ft).

Gloucester Point Beach is managed as a public park by Gloucester County (pop. about 37,000). In addition to the beach there is a 95 m (310 ft) long fishing pier with a 97 m (320 ft) “T” on the end, a small, seasonal concession stand, restrooms, an outside, freshwater shower, an open-sided shelter, numerous picnic tables, and a few pieces of play-ground equipment. There are no lifeguards. As the only public beach in the county, the park experiences extensive daily use through the summer months and on sunny weekends in the spring and fall while the water temperature is comfortable. The pier is used throughout the year.

Immediately southward of the southeast (boat ramp) end of the beach, the submerged river bank slopes very steeply to a depth of about 12 m (40 ft) within a few meters to depths in excess of 18 m (60 ft) fairly close to shore. The beach angles away from the channel so that at the fishing pier, about half-way along the public beach the ~-2m (-6 ft) contour is approximately 90 m (300 ft) offshore. The constriction of the York River between Gloucester Point and Yorktown contributes to the beach’s other potential hazard: an average ebb current of 1.6 knots (0.8 m/s). With a strong northwest wind, the ebb current can be substantially stronger. Fortunately, most of the visitors to the beach prefer the portions of the park farther away from the point itself.

Gloucester Point is the down-drift end of a coastal cell. The rigid side of the boat-ramp near the tip of the Point serves as a groin keeping the sand from flowing into the York River’s deep channel. The small breakwaters and the revetment immediately up-drift of the park’s beach were constructed a few years ago. As yet, they have no apparent negative consequences on the public beach. As the beach is situated between artificial headlands and there is no regular swell, storm waves are the major, perhaps only substantial, agents of change. The park is inundated about once a year by high water resulting from a tropical storm or nor’easter.

Though not exceptional in either a geological or esthetic sense, Gloucester Point Beach is an excellent example of a well-used community beach. It is a major recreational asset to the locality. As is the case in many areas, public access to the shore is severely limited so a community beach, such as the one at Gloucester Point, serves an important function.

Rømø Island, Denmark; By Andrew Cooper

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

Rømø Island is the southernmost of the Danish North Sea barrier islands. It forms part of the Frisian island chain that stretches from the Netherlands to Dennmark and which encloses the Wadden Sea, a vast area of shallow lagon and tidal flats. Rømø is linked to the mainland by a 9 km-long concrete causeway.

Rømø is separated from the German island of Sylt by a tidal inlet but the two are intimately linked and form part of a barrier island chain. Since beach nourishment started on Sylt, additional sand has been carried northward by longshore drift where it ‘leaks’ across the border (the tidal inlet) and adds to the sand volume on Rømø. Despite this addition of sand, the beaches of Sylt and Rømø are quite different.

The beach at Rømø is 10 kilometres long and up to 2km wide. In fact its narrowest point is still almost 700m wide. The beach is composed of hard, well compacted fine sand and much of it is still above the high tide mark. This makes it ideal for vehicle access and thousands of cars, motorhomes and other vehicles regularly drive onto the beach. Although parts of it then resemble a car park, there is such a vast expanse that much of the beach is still empty. Despite the large numbers of cars the beach has a Blue Flag award.

A particularly impressive feature of the beach is the annual Kite Festival (Dragefestival) on the first weekend of September. During the festival hundreds of brightly coloured kites of all shapes and sizes are flown on the beach, taking advantage of the persistent westerly winds. Visitors also exploit the winds for kite boarding, kite buggying, windsurfing.

The winds also produce large dunes behind the beach and indeed, most of the island is covered in undeveloped sand dunes.

The photographs above, show the beach and dunes during the 2012 Kite festival.

Cape Espenberg, Alaska; By Owen K. Mason

By Owen K. Mason, Research Affiliate, INSTAAR, University of Colorado

Cape Espenberg lies on the Arctic Circle at the terminus of a 30 km long mainland attached beach ridge plain at the northern limit of Seward Peninsula, in western Alaska. At the entry of the shallow Kotzebue Sound embayment, Cape Espenberg faces a potential open water fetch of 1000 km across the Chukchi Sea, an impact that is restricted by a perennial ice cover decreasing in duration the last 10 years.

Cape Espenberg, located 40 km east of a pronounced easterly deflection in the coast, is the depositional sink of a 200 km long littoral transport system fostered by a dominant west to northwest wind regime. Due to an abundant offshore source, sandy barrier islands front most of the northwest facing Seward Peninsula from Bering Strait into Kotzebue Sound, enclosing several extensive lagoons. The Chukchi Sea is microtidal < 50 cm, and the prevailing westerly currents maintain a series of widely spaced offshore bars that typically damp onshore wave energy. Storm surges occur with some regularity in the fall, with the extreme events, attaining a maximum elevation of 3 to 4 meter. The beach is extremely planar and composed of comparatively well-sorted fine and medium sand, with a few stray cobbles of uncertain but probable ice-rafted origin. Dunes occur in the back beach, stabilized by grass, attaining a height of ca. 4 m. The sand is considered by geologists to reflect multiple sources. Its most common constituent, a fine quartose sand is most dense on the shallow shelf north of Bering Strait and reflects a complex history. A significant amount of Yukon River sand entered the southern Chukchi Sea during the Holocene transgression, hypothetically forming and reworking a series of early Holocene barriers into a retreat massif similar to that of the mid-Atlantic. A secondary source of sand may be as a fluvial addition from south-trending paleo-Noatak and Kobuk rivers cross the exposed subcontinent of Beringia, and reworked into Pleistocene dunes during lower sea levels. The dark medium sand reflects updrift bluff erosion of a tephraeous maar eruption about 17,000 years ago. Sand supply is maintained by onshore transport during a five month open water period from June to November. Although in the long-term, as established by geological 14C ages, over the last 4000 years, sand transport is onshore and progradational, in the short term, storms and transient current reversals lead to offshore transport and erosion of Espenberg beaches. Locally, beaches have witnessed significant width and depth reductions in the last five years; current reversals are also possibly more common. A variety of clastic additions are common on the beach; these include the bones of Pleistocene megafauna (mostly horse, bison or mammoth), modern and ancient shell valves. Drift wood is concentrated in the storm beach and within the mouths of surge channels that cross cut the beach ridges. The wood, mostly spruce (Picea spp. ) is transported from the forested Yukon River drainage; cottonwood and birch are rare. Current reversals, resulting from easterly winds, lead to beach erosion, and are often coupled with the deposition of starfish and of eel grass from the enclosed lagoon. Lying wholly within tundra, dune formation is furthered along the Espenberg beach by the winter drying of beach sand, onshore winds in late spring, and the dominance of sand-burial tolerant beach grass (Elymus spp.). High dunes correlate with heightened storm events during the Little Ice Age and contain evidence of shell beds emplaced during storm surges. Intense storms produced erosional truncations across the spit between 1000 BC and AD 200 and during the Little Ice Age. The beach featured lies about 1 km Northwest from the navigational light at the Cape and can be considered unaffected by human processes, since the National Park Service restricts the use of motor vehicles and the region is nearly uninhabited. The closest settlement is ca. 10 km away and consists only of several cabins used seasonally by Inupiat hunters and fishers.

Caladesi Island, Florida; By Tonya D. Clayton

By Tonya D. Clayton, PhD

Caladesi Island is a small, sandy island (half-island, actually) perched just off Florida’s sunny west coast. As one of the area’s few undeveloped barrier islands, Caladesi sports a beautiful beach and a rare virgin stand of South Florida slash pine. Sand dunes, a maritime oak forest, and tangled mangrove swamps round out the scenery.

The landscape wasn’t always like this on Caladesi, though, nor will it stay this way. That’s the nature of the coast.

Caladesi belongs to a string of barrier islands said to be one of the world’s most diverse in terms of its collection of island shapes. Some members of the group are high and wide, with shady oaks dripping Spanish moss. Others are low and skinny, with bare sands washed by every storm.

Even Caladesi’s own shape is ever changing, century to century, year to year. A brief tour of Caladesi’s life history, as pieced together by University of South Florida geologists, illustrates how seemingly small changes in island influences can produce dramatic and sometimes surprising island transformations.

Geologic History
About 7000 years ago, sea level was rising and Caladesi Island did not yet exist. Visitors would have seen a quiet, shallow sea with grassy marshes, perhaps like today’s Big Bend area to the north.

About 5000 years ago, sea level stabilized, making conditions friendlier for island formation. An underwater sand bar grew into a long, linear ribbon of island sand. The south end grew high and wide. The remnants of an ancestral gap (inlet) in the ancestral ribbon can be seen where the marina is today.

About 4000 years ago, sea level began to rise rapidly again. Encroaching waters submerged much of the young island.

About 3000 years ago, sea level again stabilized and the island enjoyed another growth spurt. More high sandy ridges accumulated, providing hospitable ground for today’s distinctive oak forest. Watery mangrove swamps on the island’s sound side thrived and spread. You can visit these features today via foot trail and kayak trail.

Recent History
In 1921, a ferocious hurricane blasted open a new inlet, snipping the long, sandy island into two pieces. The southern piece is what we know today as Caladesi Island. With currents now flowing through the new inlet (Hurricane Pass), Dunedin Pass, at the island’s south end, was deprived of some of its sweeping tidal flow. The older pass began to fill with sand and shrink.

Over the next several decades, we humans built causeways to neighboring islands and filled in portions of the surrounding shallow waters. Tidal flows again adjusted. Dunedin Pass continued to shrink.

In 1985, Hurricane Elena passed by offshore. Storm waves further rearranged local sands, setting the stage for the death of Dunedin Pass and the birth of a new, short-lived pass (Willy’s Cut) to the north.

In the years since, Caladesi Island has continued its shape-shifting ways. Dunedin Pass has completely closed, joining Caladesi and Clearwater Beach Islands. A once-tidal waterway is now a landlocked pond. Ephemeral inlets come and go.

In summer 2012, Tropical Storm Debby sauntered by. Sustained high winds and roiling seas shifted truckloads of sand from south to north and from beach/dune to offshore bar. A grassy front dune line disappeared, along with sea-turtle and shorebird nests. Trees toppled. Once-buried peat and mud emerged, dark and sticky, from the thinned sands.

In Debby’s wake, the dance of the sands has continued, though at a less dramatic pace. Rain and gravity have softened once-sharp dune scarps. The muddy outcrop has disappeared. New dunes are taking root in half-buried piles of post-Debby wrack. Island life goes on.

Today
Caladesi Island is now part of the much-loved Caladesi Island State Park. The Florida Master Naturalist Program and the Great Florida Birding and Wildlife Trail highlight this unique barrier as a great place to experience natural coastal features and see not only shorebirds but also migrant songbirds.

Hundreds of thousands of people visit each year, arriving by boat and on foot. Many more know the place through the vivid recollections of Myrtle Scharrer Betz. She wrote Yesteryear I Lived in Paradise, an award-winning account of pioneer life with her father on Caladesi.

Modern management challenges are varied, ranging from seagrass-plowing jet skis to aggressive plant invaders. A new concern is the growing popularity of kiteboarding: large, fast-moving shadows can startle and scatter birds into flight. Even passersby quietly strolling the beach may disturb shoreside animals in need of food and rest.

Sea level is on the rise again, at a rate of about 15 centimeters (6 inches) per century according to regional tide gauges.

Out on the beach, you’ll find that no two Caladesi visits are the same. In one stretch, hungry waves upend chunky palm trees. In another, winds and sea oats work together to build new dunes. Some days the wrack is good, and shorebirds vigorously work the drift line. Other days the rains are good. Multinational feathered flocks will gather later at short-lived beach ponds.

The unmistakable signs of beach change and island evolution are ever present at Caladesi “Island.”

Tonya D. Clayton, PhD, author of How to Read a Florida Gulf Coast Beach.

Ancient La Caleta Beach and Cove; By Cecelia Dailey

By Cecelia Dailey,

From the south, the route to the ancient city of Cadiz moves through rolling hills lined with windmills, then miles of estuary and flooded fields along the Andalusian coast of Spain. Abandoned and living mouths of alluvial rivers deposit sediment to the ocean and along the shore here. In the Gulf of Cadiz, rich marshlands flourish. But the city of Cadiz is different—it is built on what was once a rocky archipelago, now a half-mile wide peninsula. Sand, silt, and other sediment deposited over the last 6500 years have filled the space between the islands, allowing successive cultures room to expand. [1] A narrow strip of land only wide enough for a road and beach connects the peninsula of Cadiz to the south. At the peninsula’s northern end is the unique fan-shaped city of Cadiz. [2] Though it faces the waves of the open ocean, Cadiz has persisted through storms over the centuries and is one of Europe’s oldest cities. Changing geography has shaped the seafaring cultures that made their home here, and in turn, its people have shaped Cadiz into a fortress of a city that is inflexible to the dynamic coast.

Beloved by locals and tourists alike, La Caleta is the only open beach in the walled city of Cadiz. A boardwalk forms the border between the beach and city; an adjacent cafe is good vantage point for watching people play and pick up stones on the shore. Central to the 360-meter long beach is a white pavilion raised above the sand on pilings. On each side of the beach, two ancient reef structures extend into the Atlantic, calming the waters of La Caleta’s harbor. Acting like two straight jetties, the fossil-filled reefs form a channel into the swooping C-shaped beach and shallow bay. Two castles sit atop the rocky outcroppings that border the beach. Connected to the shore, Santa Catalina castle is the beach’s northernmost point. In the distance, San Sebastian castle and its long promenade form the southernmost border of the beach and bay.

Changing geography has shaped the seafaring cultures that made their home here…
—Cecelia

Both of La Caleta’s castles were completed during Spain’s wealthiest age, lasting over 300 years, when trade with the Americas necessitated protection of the city. [3] Though the port is located on the opposite side of the peninsula, the castles served as a strategic point of defense on the Atlantic. Designed as fortification, Santa Catalina was built as a direct response to an English sack that devastated the city in 1596, and by the mid-sixteenth century Cadiz was fortified with essential defensive features such as gates, towers and walls along its perimeter. [4] At that time, Cadiz’s hard-edged outline had taken form, looking much like it does today.

When visiting this past winter, historic photographs, artifacts and maps cataloging early settlements of Cadiz were on display at Santa Catalina castle—today used as an exhibition and event space. Charts and drawings shown are from a 1982 archaeology study by J.R. Ramirez, who now heads the city’s history museum. [5] According to the exhibition text, there was no such beach at La Caleta in the past, but between the reefs of La Caleta was the Canal Bahia-Caleta, or Bay-Cove Canal. If it existed today, the canal would cut through the modern-day city and connect to the port-side of Cadiz.

In the model displayed, the land is divided into three major islands by the canal, with many small islands along its rocky outcroppings. Part of the Bahia-Caleta was detected in 1926 by a mining engineer named Juan Gavala y Laborde who suggested it was an ancient river mouth. [8] The canal was renamed the Canal de Ponce for the author of the 1976 study that confirmed its existence below the city. [1]

A windy outcropping jutting into the Atlantic, where San Sebastian castle sits today, is depicted in a colored etching at the exhibition (Braun & Hogenberg, c. 1598). It shows fishermen out on rocks, a wall along the shore, and quarrying in the harbor at La Caleta adjacent to a chapel. The medieval chapel was dedicated to Sebastian, the saint said to protect from plague—in the image, a white-robed Catholic clergyman (holding a rosary) faces a man in black, presumably death. There is evidence of an earlier Punic-era shrine at San Sebestian’s location too. [5, 6]

From the beach, the 1706 fortification is visible in the distance, connected by a 19th century boardwalk. Possibly the location of an ancient shrine to Kronos, interpreted by the Romans as the god of time, this location has been revered for its poetic and spiritual qualities and provided refuge from the foreboding sea. A feeling about this place persists—to be in Cadiz is to be on the edge of the world.

On display at Santa Catalina was a collection of Roman amphorae, ceramic cargo containers, evidence of Cadiz’s history as a hub for commercial fishing and trade. Some amphorae date from the Punic times, when Phoenicians, Cadiz’s earliest known inhabitants (c. 7th or 8th century BC) used La Caleta as inlet to an interior port at a time when the area was divided into islands [9]. Evidence of a port in the canal has been shown by Oswaldo Arteaga, J. R. Ramirez and others. [1,5] Sometime during antiquity, the port was most likely moved to the gulf-side (west coast) of Cadiz because the Bahia-Caleta was filling with sand making navigation difficult. Today, small wooden boats float in the bay at La Caleta beach, and at low tide, the boats sit out on rock flats. Although no longer booming, port commerce and fishing industries are still significant to Cadiz’s economy.

Arteaga explains the physical and cultural chronology of this area in his 2008 article included in a volume exploring the geologic history and archaeology of Cadiz. Around 6500 BP (before present), there were many small islands, the Bahia-Caleta canal was open, and there are none or very few marshlands. By 3000 BP (around the time of the Phoenicians), an isthmus formed, bridging the Bahia-Caleta canal and connecting the major islands; the Isla de Cadiz is united with San Fernando (an island to the south), forming a larger landform; the wetlands grew with sediment deposited from rivers. Around 1000 BP, when much of Spain was under Islamic rule, the shape of Cadiz’s old city is recognizable and the channel is filled in. La Caleta beach is the historic site of the canal’s mouth to the west; the port is to the east. [11]

Walking along the beach, weathered rock, rounded stones, and pieces of ancient coral are washed up on the sands of La Caleta and collected along castle walls. Some light umber-colored rough rocks give an idea of what Cadiz is seated on—porous rock, composed of sedimentary sandstone and conglomerates. The castles are made from a brown stone embedded with fossilized shells, and strolling the narrow winding streets of the medieval city, there are many intricately carved facades of the same material. Possibly quarried from La Caleta beach or another site nearby, this is what the locals call “oyster rock” or “piedra ostionera”–a cemented conglomerate rich in shells from the Tertiary age. [12]

For at least the last century, La Caleta beach and the coastline of the Cadiz province have been in recession and many beaches have been artificially restored in order to stabilize them.
—Cecelia

Seated along faults, a series of tectonic events gave Cadiz its peculiar morphology, producing a depression that filled to become the gulf. [13] There are also deposits in the gulf that indicate tsunami activity. [14]

The beaches of Cadiz, said to be among the most beautiful in Spain, have nearby high-rise buildings and structures. Most of the old town, however, lacks such urban density and has open plazas and gardens with tiled walkways and fountains. Cadiz underwent a period of dramatic growth beginning in the 1940s until the mid-70s, focused on building the city as a tourist destination, and included high-rise projects, mostly to the south of the old walled city. [15] On a narrow peninsula like Cadiz, coastal forces are never absent and high-rise buildings are always close the sea.

For at least the last century, La Caleta beach and the coastline of the Cadiz province have been in recession and many beaches have been artificially restored in order to stabilize them. A 1998 Coastal Engineering article reports that: “During the last decade, more than [12 million cubic meters] of sand have been nourished in 38 restoration operations carried out on 28 beaches” in the Cadiz region. La Caleta, about 50 meters wide, is one of the smallest of the Cadiz beaches. 41,440 cubic meters of sand (mixed with silt and shells) was added as beach nourishment material to La Caleta at a total cost of US$81,032 in 1991. Sand used for La Caleta’s nourishment project was sourced offshore from Cadiz’s Cortadura beach, located to the south of La Caleta. Other dredge sites for this region are located in Cadiz’s harbor, facilitating its port and shipping channel.

In the Cadiz province, beaches were nourished between one and three times in the 1990s. [16] Beach nourishment projects around Cadiz have been generally well-accepted by the public and said to have “relatively good performance after more than 13 years” of study. [17] However, when a beach is in recession, nourishment must be repeated to achieve the status quo. Dumping sand on the beach destroys beach life, sand washes away, and dredging rips into seafloor, potentially impacting sea life as well as covered artifacts and shipwrecks. Nourishment gives the illusion that the beach is a static feature—however, erosion is constant, and in a balancing act with forces of sediment deposition, coastal environments are always changing.

Erosion in the Gulf of Cadiz is directly related to dams that prevent sediment from flowing to the sea, according to the 2002 University of Cadiz study. Spanish hydraulic policy in the 1960s through the 90s spurred the construction of dams at many points along the rivers that drain the Andalusian Plain, including the Guadalaquivir, Guadiana, and Gaudalete rivers. Consequently, coastline retreat, low in the 70s, progressively accelerated through the 80s, leading to widespread shoreline erosion. Hardened shoreline structures also contribute to beach loss and shoreline erosion in Cadiz. [18] Rates of erosion on La Caleta, or any ocean-facing beach, vary with the intensity of storms from year to year.

Located at the mouth of the shallow Guadalete River, Cadiz is about 30 miles south of the mouth of the Guadalquivir River, the only large navigable river in Spain. Romans sailed from the Atlantic inland to Cordoba by way of this broad, gentle river, but today, the mouth of the Guadalquivir River is choked by sandbar formation. [19] During the 18th century, these sandbars caused, in part, the Spanish government to shift their trading post from upriver Seville to Cadiz, a testament to the dynamic character of rivers in this region. [3] This area is now the Doñana National Park, established in 1963 to protect the marshy river delta. [20] The nearby Natural Park of Cadiz, a region of wetlands, was established in 1989. [21] Protection of these areas as parks allows their dynamic character not to be impeded upon and complex ecology to flourish along the coast.

No expansion of Cadiz’s border is happening here today, prohibited by Spain’s law governing coastal development. The “Ley de Costas” or “Coastal Law” creates a zone of public domain along the beach, surf zone, areas of historic storm infiltration, and areas reclaimed by the sea. Restricted zones 100 meters inland from the beach allow private ownership only of structures built prior to 1988. [22] The 1978 Spanish constitution considers the beaches to be publicly owned (Article 132). [23] How the law will be implemented in Cadiz in unclear, as much of the city seems to fall under the public zone, and if it faces damage from a storm, rebuilding might not be permitted.

Spain’s law aims to protect and preserve their coast in the most natural state as is possible. Tourism is an essential part of Spain’s economy, especially today, and their coastal laws are an effort to ensure that coastal landscapes are not degraded due to competing interests. Coastal law in Spain has been controversial, and even more controversial has been the enforcement of the law through demolition of illegal construction. [24] With advancing sea level rise, Spain’s plan for its cities to recede from the beach is wise. With much of Cadiz sitting on land protected by hard structures and seawalls, might Cadiz persist another century as a living city or will it become a relic, like the deteriorating artifacts that surround it on the seafloor? As a tourist sitting on La Caleta beach, the scene is peaceful and gentle waves lap the shore.


Google earth map of cadiz with locations of important features marked: Google earth map

For further study of Cadiz’s geography and cultures, one of the best resources is: the No. 10, 2008 issue of RAMPAS (Atlantic-Mediterranean Journal of Social Archaeology and Prehistory) containing 16 articles published in Spanish.


FOOTNOTES:
[1] Oswaldo Arteaga Matute, Geoarqueología y Proceso Histórico en la Bahía de Cádiz. Revista Atlántica-Mediterránea de Prehistoria y Arqueología Social 10.Cádiz: Universidad de Cádiz, 2008.

[2] Google earth map of cadiz with locations of important features labeled: Google earth map

[3] Parry, J. H., The Spanish Seaborne Empire, from The History of Human Societies series.

[4] Port Cities of Atlantic Iberia, C. 1500-1900, Patrick O’Flanagan, 2008.

[5]Ramirez’s 1982 study of its earliest dwellers. JR Ramirez

[6] Sobre la topografía de Cádiz en la Edad Media, Museo de Cadiz.

[7] Puerto Chico Cadizipedia.

[8] The Phoenicians in Spain: An Archaeological Review of the Eighth-Sixth Centuries B.C.E., edited by Marilyn R. Bierling, Seymour Gitin.

[9] “Fish-Salting Plants and Amphorae Production in the Bay of Cadiz (Baetica, Hispania). Patterns of Settlement from the Punic Era to Late Antiquity”, Bernal, D., & Sáez Romero, A. M., 2008.

[11] PROBLEMÁTICA Y SITUACIÓN ACTUAL DE LA ARQUEO- LOGÍA SUBACUÁTICA EN LA BAHÍA DE CÁDIZ, 1998. Read More

[12] ©© Tashland Schmidt, Macau, Figueras, Benjumea, and Goula, 2009.

[13] “Geology in the vicinity of the city of Cadiz”, Salvador Dominguez-BELLA, 2008, RAMPAS No. 10.

[14] The Tsunami Threat

[15] European Architecture Students Assembly (EASA), Cadiz case study.

[16] Cost of beach maintenance in the Gulf of Cadiz (SW Spain), Coastal Engineering, 2000.

[17] A Critical Reivew of Urban Beach Nourishment Projects in Cadiz City after Twelve Years” 2004

[17]“The quantification of coastal erosion processes in the South Atlantic Spanish coast: Methodology and preliminary results” University of Cadiz, 2002.

[18] “The Punta Umbria (Huelva) Spit”, Coastal Engineering, 1992.

[19] Doñana National Park, UNESCO World Heritage Center.

[20] Andalusia.com, Natural Parks—Cadiz Province.

[21] Ley de Costas—Coastal Law.

[22] 1978 Spanish constitution.

[23] “Spain bulldozes its concrete costas” December 6, 2007.

Faroe Islands; By Adam Griffith

By Adam Griffith

The Faroe Islands are a group of small volcanic islands that lie between Iceland and Norway in the northern Atlantic (Figure 1). These islands are relatively young, 55 million years old, and consist of alternating layers of basalt and tuff.

The young age of the islands and the high energy waters of the North Atlantic combined with the steep slopes of the Faroe’s rocky coastline make the accumulation of sand rare. However, tucked away in the sheltered coves of many of the islands are small (< 300 m long), sandy, pocket beaches like Sandager (Figure 2). Located just south of the islands’ largest city, Torshavn, Sandagar is an east-facing beach sheltered from the waves of the Atlantic by the island of Nolsoy (Figure 3). The deposition of river sediment and the lack of high energy wave action along this section of coast allows the sand to accumulate at the mouth of the Sanda River. The source of sand for Sandagar beach is material eroded from the mountainous terrain of the islands themselves carried to the ocean by the river. As the river nears the coast, the waters slow and sand (Figures 4 and 5) falls out of suspension and is deposited at the beach. Most of the streams and rivers of the Faroe Islands plummet over sea cliffs into deep waters making beautiful cascades (Figure 6), but rarely forming beaches as a result. Unlike much of the inhabited world, the Faroe Islands do not have a long history of human influence; they were discovered by Irish priests around 750 AD sailing the open ocean in small boats called coracles. The Faroe Islands provide a rugged habitat for life and therefore were not permanently inhabited for several hundred years after their discovery. No mammals are native to the islands and the only trees there have been brought from Europe. Despite its location at 7 degrees north latitude, winter temperatures are mild ~ 3-4 0 C and summers are also cool ~ 10 0 C. Still unknown to many people, the Faroe Islands have become more familiar to some recently due to a variety of media mentions. They were written about in Jared Diamond’s 2005 book Collapse. In 2007, the islands were chosen by National Geographic Traveler magazine as the top island destination in the world. Lastly, the 2009 movie The Cove brought into the mainstream the complex and controversial issue of traditional whale and dolphin hunting practiced in Japan and The Faroe Islands.

Quendale Beach, Shetland Islands, UK; By Joe Kelley

By Dr. Joe Kelley, Department of Earth Sciences, University of Maine

Quendale Beach is on the southern side Mainland, the largest of island in the Shetlands. The Shetland Islands, of course, are a part of Scotland, though they are usually shown on an inset map of the UK because they are farther north than parts of Norway. This is a treeless landscape with strong winds and large waves during storms. Swimming is possible, but the water is cold and a wetsuit is advised even in the summer.

The Quendale Beach is a beautiful and tranquil, however, with visitors who prefer solitude to glitz (Figure 1). It is a clean sand beach about a kilometer (little over a half mile) long. There are rocky headlands at either end, with scattered farms and archeological sites, and no commercial development near the beach. It is easily reached by a dirt road through gated sheep farms, but the sheep and farmers are friendly and welcoming.

… Possibly owing to frequent large storms during the climatic event known as The Little Ice Age, or overgrazing by introduced sheep and rabbits, the sand dunes broke down and wind-blown sand swept across the area. The nearby community was overwhelmed by sand, described by a visitor as another “Arabia”…..
—Dr. Joe Kelley

Sand dunes up to 15 m (50 feet) high back the landward margin of the beach (Figure 2), but a path through them was cut to permit easy access. The dunes appear to be eroding today, but enough sand remains in most places to insure a long and stable future. One exception is a dreadful area where sand mining occurred in the back dunes in the 1970’s. Half a million to a million cubic yards of sand were unwisely extracted, reducing the back dune elevation to the water table for more than a hundred meters (Figure 3). Generally this area is used for parking and informal camping (typically by touring bicyclists) today.

Though it is bucolic today, two historic events marred the tranquility of the region. In 1969, the oil tanker MS Braer crashed against the rocks nearby, releasing 85,000 tons of crude oil. This was an extraordinary disaster, but an ambitious clean up, big storms and time have completely healed the beach. Today, no oil whatsoever can be seen, and shorebirds like gannets, razorbills and puffins abound on the cliffs.

The other act of violence against the calm of the area occurred in the late 17th Century. At that time, the valley behind the Quendale Beach was among the most valuable and productive farmland on the island. Possibly owing to frequent large storms during the climatic event known as the Little Ice Age, or overgrazing by introduced sheep and rabbits, the sand dunes broke down and wind-blown sand swept across the area. The nearby community was overwhelmed by sand, described by a visitor as another “Arabia”.

Houses and eventually the entire settlement was abandoned as migrating sand and dunes eventually buried everything. The community was literally removed from the map by the disaster. Today, archaeologists are digging through the sands to glimpse remains of life from that period (Figure 4).