So Much to Learn About the Oceans From Sand
Photo Source: National Geographic
By Cornelia Dean, The New York Times
As a young geophysicist in the 1980s, Rob Holman attended a conference in San Francisco that included a field trip to a beach. Dr. Holman, who grew up inland, in Ottawa, stared at the ocean, assessing the strengths and vectors of the waves and currents. But when he looked around, everyone else was studying the sand.
He realized, he recalled, that “sand is not the same everywhere.” So he started collecting it. “I collected a few samples and put them in jars,” he said. “Then I had so many I built a rack. Then I built three more racks. Then I built four more.”
Today Dr. Holman is best known as a coastal oceanographer at Oregon State University whose computerized photography system, called Argus, has given researchers new ways to observe and measure beaches. But he still collects sand, which he displays on shelves in the corridor outside his office. By now he has almost a thousand samples. They come from his travels and from geologists and amateurs all over the world (including this reporter) who send him grainy shipments in envelopes, plastic bags, paper towels and other wrappings. Each offering is dried and transferred to glass laboratory jars a few inches high, which Dr. Holman labels by latitude and longitude of their site, as best he can determine them from the sometimes sketchy information his contributors provide.
The collection includes sand from all continents, including Antarctica. “Dutch colleagues are particularly good” at mailing in sand, Dr. Holman said. “Africa is lacking in samples,” a deficiency he attributes in part to an unfortunate accident. “Early on, I had a rack collapse,” he said.
Though these offerings have not necessarily ended up in the formal display, he has also received a bottle containing a gimmick portrait in purple sand, Hawaiian sand samples sold in packages to tourists, salt and pepper (“that was actually my secretary”) and all kinds of other things that were found on beaches, or might have been, including jelly beans and M&Ms. He accepts contributions of sand from inland riverbeds and places like Ayers Rock, in the Australian Outback, and even from hotel lobby ashtrays “if it’s a high-class place,” he said. These are listed as “miscellaneous.”
For Dr. Holman, what started almost as a joke has become a valuable teaching tool. Geology students at the university study his collection, and they can learn a lot from it. “This row is a north to south transect along the East Coast,” he said one day recently, pointing to tubes containing samples collected at sites from Cape Cod to Key West. “It just gets lighter and finer.” That is because most of the time sand is not stationary on the beach. On the East Coast, “the big waves come in from the northeast, and they drive the littoral drift predominantly from north to south,” Dr. Holman said, referring to the longshore movement of sand.
By the time a grain of sand washes up on a beach in Florida, it has been battered by waves for a long time. “The physical action of being continually beaten causes the grains to break down, the angular corners to break off,” he said. “They become more rounded.”
And relatively dense mineral grains, like garnet, have settled out. The result is a row of samples shifting from the relatively dark, coarse grains of the Northeast to the fine white beach sand of the Southeast.
Dr. Holman keeps about two dozen especially telling samples in a portable “teaching rack” for use in classes and at lectures. Some are dark volcanic grains. One vial, from the Banzai Pipeline, a surfing mecca in Oahu, “is all broken up shells with rounded edges,” he said. “This sand cannot last very long.”
The rack “illustrates a lot of the things we need to know about how beach sands are different,” he said. “I have occasionally taken in sand to a student exam and said, ‘Tell me about this beach.’ A good person can do very well. There are a number of characteristics you can look at — the nature of the sand and the shape, where would the minerals come from, different transport and aging. Those all affect the sand you see on the beach.”
Dr. Holman also takes the teaching rack with him when he gives talks to the public, an effort to encourage people “to think about what they see on beaches.”
“Then I show them some Argus pictures, which always make them think about sandbars and how mobile they are,” he said.
Argus is the system Dr. Holman developed in research he began about 20 years ago at the Army Corps of Engineers research pier on the coast at Duck, N.C. Researchers assigned to the Duck pier regularly send instruments into the surf to make precise measurements of the underwater topography in the surf zone, particularly the formation and movement of sandbars along the beach.
Understanding these sandbars is critical to study of beach erosion and climate-related sea level rise, but the surf zone is a notoriously hostile research environment. Setting up and maintaining instruments there is almost impossible unless the equipment is so sturdy it distorts its own data, by interfering with the flow of water and sand. As a practical matter, the measurements made routinely at Duck are unobtainable almost anywhere else, and certainly not here in Oregon, where the wave climate is the harshest of any coastline in the Lower 48.
Dr. Holman used the Duck instrument data and time-lapse film from a camera he mounted on a tower at the Corps installation to figure out how to correlate photographic information to changes in the topography under the surf.
The results were surprising. For one thing, sandbars were not moving in simple patterns, as many coastal scientists had thought they did. “The biggest thing we learned is how much more complicated it is than we thought it was,” he said. “There is a richness of morphologies.”
Using Argus data, scientists can watch, almost in real time, as sandbars appear, disappear, curve, drift, breach and otherwise act up under the camouflage of breaking waves. The system can even be used to spot rip currents in real time. The lesson of Argus, he said, is “never give up observing”
S. Jeffress Williams, a coastal geologist with the United States Geological Survey, called the system “a critical piece of new technology.”
“The Argus system allows us to quantify and document visually the changes that take place along the coast on a variety of different time frames,” he said. Dr. Williams, a contributor to Dr. Holman’s collection, said that without the system, these observations would be difficult or even impossible. “A lot of the changes take place during storms and at times when it is difficult to have people out on the beach making observations and taking measurements.”
At one time, Dr. Holman said, coastal scientists thought that if they understood all the underlying physics, they would understand everything about beaches. “The pendulum has swung back,” he said. “Argus has been part of that. Argus helped us realize that our simple concepts were simple.”
While it is true that all beaches “live by the same rules” in that the movement of wind, water, waves and sand is always a matter of F = ma (force equals mass times acceleration), beaches behave differently. “We hope to figure that out,” he said.
Today, there are Argus installations at Duck and in Oregon, California, Hawaii, England, the Netherlands, Australia, New Zealand, Spain, Italy and Brazil.
Dr. Holman has also begun working with NATO in hopes of adapting routine reconnaissance images, most of which are discarded, to the Argus system.
Meanwhile, sand keeps piling up. When he first displayed the collection, Dr. Holman said, “the dean was a little queasy” about investing in shelving. But now it may be time for another infusion of money. Though he installed shelves with what he thought was ample room, he said, “we have run out of space.”
Rob Holman of Oregon State University with sand samples from nearly 1,000 sites around the world.