Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers recognize ’lower-energy’ varieties of coastal islands

16.03.2005


A different style of coastal barrier islands that forms under lower-energy conditions than classic ocean-facing barriers, such as North Carolina’s Outer Banks, has been identified by coastal geological researchers at Duke University and the University of Ulster in Northern Ireland. The new style of islands is typically found in protected bays and lagoons.



"This is a major and important recognition," said Orrin Pilkey, a geology professor emeritus at Duke’s Nicholas School of the Environment and Earth Sciences, who directs the university’s Program for the Study of Developed Shorelines. "It’s a type of island quite different from the standard barrier islands on the open ocean."

"There are some people who would argue that these aren’t barrier islands," Pilkey said. But Pilkey, University of Ulster geology professor J. Andrew Cooper and Duke undergraduate David Lewis believe they can identify more than 20,000 uniquely "fetch-limited barrier islands" existing globally along the coastlines of every continent except Antarctica.


Lewis, a senior in Duke’s earth and ocean sciences undergraduate program who has been researching fetch-limited barrier islands for two years, will describe the group’s findings on Thursday, March 17, 2005, at the annual meeting of the Geological Society of America’s Southeastern Section, to be held at the Grand Casino Resort’s Bayview Hotel in Biloxi, Miss. The research was supported by the University of Ulster.

Lewis said these islands are called "fetch-limited" because he has found none that encounter wave-producing wind fields -- the geophysical definition of "fetch" –- any longer than 300 kilometers.

Classic barrier islands are built and sustained by fetches longer than 300 kilometers that deliver wave energy from the open ocean. Studies have shown this wave power delivers nourishing supplies of sand sufficient to renew such islands following the severest of coastal storms.

Fetch-limited barrier islands are like the ocean-facing variety in being located along coastlines, separated from the mainland, said Lewis and Pilkey. But they are different in their wind- and wave-shielded settings.

Unlike barrier islands, numbers of fetch-limited islands are located within bays such as Maryland and Virginia’s Chesapeake. Others occupy lagoons such as Mexico’s Laguna Madre. And some are protected by coral reefs such as those behind Australia’s Great Barrier Reef.

Fetch-limited barriers also tend to be smaller than ocean-fronting barriers, the Duke researchers added. The average length of short-fetch islands is only about 1 kilometer, as demonstrated by 105 examples along Delaware Bay. By contrast, North Carolina ocean front barriers have average lengths of 21 kilometers, while those in Texas average 54 kilometers.

Deprived of the presence of significant surf zones, fetch-limited barrier islands seem to depend uniquely upon periodic storm overwash or spring high tide events to provide fresh sand supplies needed to sustain them. "There is definitely a gradation of these islands, based on their wave energy," Lewis said. "The higher the wave energy, probably the bigger and longer the island."

Another difference in fetch-limited barriers is their relative greenness. Surf action is weak enough to allow even wave sensitive mangroves and salt marshes to grow on these islands’ most exposed front sides, Lewis added.

Pilkey said that Lewis did the bulk of the work identifying and classifying these special islands, using extensive satellite surveys and also accompanying Pilkey and Cooper on on-site investigations as far away as Australia and Turkey.

Researchers in Pilkey’s program have spent decades documenting that the major obstacle to the maintenance of classic ocean barrier islands is human beachfront development. Their research shows that development brings obstacles such as seawalls that can interfere with natural processes.

Many fetch-limited barrier islands have escaped human development because they are too small and low or lack the attraction of an ocean view, the Duke researchers said. But development that does exist shares similarities to that on oceanfront barriers.

"Seawalls are really common on Chesapeake Bay," Lewis said. "On the New Jersey side of Delaware Bay, almost every house has a seawall in front of it."

Monte Basgall | EurekAlert!
Further information:
http://www.duke.edu

More articles from Earth Sciences:

nachricht Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>