Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Survey off San Diego Reveals Details of Sand Movements

10.04.2007
Scripps scientists find geological features control sediment buildup

An underwater survey off San Diego has revealed geological details of how sand builds up along Southern California's continental shelf and could help resource managers to locate deposits to rebuild beaches, according to a report by scientists at Scripps Institution of Oceanography at UC San Diego.

The newly acquired data show the depth of sand levels along 10 kilometers (6.2 miles) of shoreline from La Jolla Cove north to Torrey Pines State Beach and how the sediments are distributed on the shallow, gently sloping seabed adjacent to the shoreline.

The scientists also identified an area of the seafloor uplifted offshore of Torrey Pines State Park that results from a jog in the Rose Canyon fault, similar to the uplift that created Mount Soledad. This uplifted area appears to play a major role in the accumulation of sand in the area, according to Leah Hogarth, a Scripps graduate student and lead author of the article in the journal Geology of the Geological Society of America.

"This study shows how the local tectonic structure controls the long-term accumulation of sediments on this region of the nearshore shelf," Hogarth said. "There are many locations along the Southern California coastline south of Point Conception that exhibit similar right-lateral, strike-slip faults and might have similar patterns in sediment distribution."

The survey found the offshore sand thickness in the area goes from nearly zero offshore Torrey Pines beach to as thick as 20 meters (65 feet) southward toward La Jolla Cove. Adjacent to the uplifted area off Torrey Pines is a pocket of sand some 15-20 meters (49-65 feet) thick that the scientists call a "sediment depocenter." It is nearly 2 kilometers (1.2 miles) offshore at a depth of about 30-40 meters (95-130 feet), which is likely too deep to be affected by waves and climate conditions, according to Neal Driscoll, a Scripps professor and coauthor of the report.

"The study location is ideal because the geometry of the fault structure lets us separate the tectonic influences on sand accumulation from the effects that relate to sea-level fluctuations," Driscoll said. "This gives insight into where California's offshore sand resources and hardgrounds might be located on a long-term basis and could assist coastal resource managers in identifying potentially reliable sources for replenishing sand to beaches."https://www.sio.ucsd.edu/secure/eNews/releases/frm_editRelease.php?releaseID=785

According to Driscoll, the newly observed sediment thickness offshore La Jolla indicates that tectonics and sea-level fluctuations control long-term sediment accumulation in the region and that waves and long-shore currents control sediment distribution. He said this study indicates interactions between right-lateral fault segments offshore Southern California play a major role in creating pockets of sediments.

During the survey, the scientists towed a specially outfitted underwater device behind Scripps research vessel Robert Gordon Sproul making multiple passes over the 20 square kilometer (7.5 square mile) area. Onboard the device were instruments to produce images of both the seafloor and sub-bottom. The sub-bottom profiles are produced by acoustic signals that penetrate through approximately 25 meters (80 feet) of sand, showing the thickness of the sediments. The scientists estimate some 60 million cubic meters (78.5 million cubic yards) of sand are within the study area.

"Knowing where the sand deposits are stable could help make for better choices of beach replenishment sources," Hogarth said. "If we are careful to take sands from areas offshore where they will be replenished naturally or where those sands do not already contribute to the beach, we can better ensure we are not further disrupting the balance of sediment supply to beaches."

A major public works effort to restore sand to beaches along sections of San Diego County was carried out in 2001 by the San Diego Association of Governments (SANDAG). More than 1.5 million cubic meters (2 million cubic yards) of sand was dredged from offshore and pumped onto beaches in Oceanside, Carlsbad, Encinitas, Solana Beach, Del Mar, San Diego, and Imperial Beach. This was the first regional beach restoration project undertaken on the West Coast, according to SANDAG officials. The City of Imperial Beach is working on large-scale beach restoration project with a goal of periodic replenishment over the next 50 years.

Other Scripps scientists contributing to the study were Jeffrey Babcock, Nicholas Le Dantec, Jennifer Haas, Douglas Inman and Patricia Masters.

A detailed map made by the Scripps scientists showing the seafloor structure from Encinitas to Coronado can be viewed and downloaded at http://scrippsnews.ucsd.edu/Releases/?releaseID=785.

Contributors to the map are the U.S. Geological Survey; the University of New Hampshire, Durham; and California State University, Monterey Bay.

Chuck Colgan | EurekAlert!
Further information:
http://www.ucsd.edu
http://scrippsnews.ucsd.edu/Releases/?releaseID=785

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 >>>