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 Climate satellite: Tracking methane with robust laser technology
22.06.2017 | Fraunhofer-Gesellschaft

nachricht How reliable are shells as climate archives?
21.06.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>