Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Survey off San Diego Reveals Details of Sand Movements

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."

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

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:

More articles from Earth Sciences:

nachricht Gas hydrate research: Advanced knowledge and new technologies
23.03.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

nachricht New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

For graphite pellets, just add elbow grease

23.03.2018 | Materials Sciences

Unique communication strategy discovered in stem cell pathway controlling plant growth

23.03.2018 | Agricultural and Forestry Science

Sharpening the X-ray view of the nanocosm

23.03.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>