Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

California rising

04.09.2015

Spatially corrected sea-level records for the Pacific coast indicate that uplift rates are overestimated

For millions of years, the Pacific and North American plates have been sliding past -- and crashing into -- one another. This ongoing conflict creates uplift, the geological phenomenon that formed mountains along the west coast.


This aerial view shows the marine-terraced coastline of California north of Santa Cruz.

Credit: Ramon Arrowsmith via Wikimedia Commons

A new analysis by UC Santa Barbara earth scientist Alex Simms demonstrates that the Pacific coastlines of North America are not uplifting as rapidly as previously thought. The results appear in the journal Geological Society of America Bulletin.

"Current models overestimate uplift rates by an average of 40 percent," said Simms, an associate professor in UCSB's Department of Earth Science. "They do not take into account glacio-isostatic adjustment, the Earth's response to the melting and growth of past ice sheets. Previous studies of the Pacific coast, including California, have ignored this when trying to use past sea levels to calculate uplift rates."

Uplift is the vertical elevation of the Earth's surface in response to plate tectonics.

Scientists determine uplift rates by measuring marine terraces -- flat mesas that indicate where the ocean level used to be -- and comparing their elevations to geologic records of sea-level change. However, traditionally used "global" sea-level records come from places like the Huon Peninsula of Papua New Guinea, far away from the ice sheets that once covered Canada. That's a problem because the freezing of water into ice sheets and its subsequent thawing actually changed the shape of the Earth ever so slightly -- and this deformation affects ocean levels.

According to Simms, the land responds the way a mattress does, indenting from weight and then relaxing back to its original shape. The Earth's gravitation field also changes in response to the building up and melting of these ice sheets. These changes to the land and Earth's gravity cause past sea levels to vary across the world. Most of this glacio-isostatic adjustment is not caused by current glacier melt but by the rebound of the Earth from the several-kilometer-thick ice sheets that covered much of Canada 20,000 years ago.

Simms and his colleagues compiled existing elevation measurement data from more than two dozen sites ranging from mid-Oregon to Baja California. They then recalculated uplift rates for each, applying a correction for glacio-isostatic adjustment.

Some areas are affected to a greater degree than others. The uplift rate for Punta Cabras in Baja California showed the largest difference: 72 percent lower than previous estimates. The rate for the San Diego area was reduced by 62 percent. For other areas, the rate changes were not as dramatic.

"Areas in Oregon are moving so fast that when you add the correction, the adjustment is much smaller: 10 to 20 percent," Simms said. "If a site is going up 100 meters versus 90 meters, that's not a big change. Here, sea level changed differently because of the distance from where these big ice sheets used to be."

This study provides one of the first spatially corrected sea-level records for California. "A 2012 study looked at one spot with one model, but we looked at variation across the state," Simms explained. "Now our data can be applied not only in California but along the Pacific coast of North America."

###

The study's co-authors are Hélène Rouby of the Laboratoire de Géologie de l'Ecole normale supérieure in Paris and Kurt Lambeck of The Australian National University in Canberra.

Media Contact

Julie Cohen
julie.cohen@ucsb.edu
805-893-7220

 @ucsantabarbara

http://www.ucsb.edu 

Julie Cohen | EurekAlert!

More articles from Earth Sciences:

nachricht Massive impact crater from a kilometer-wide iron meteorite discovered in Greenland
15.11.2018 | Faculty of Science - University of Copenhagen

nachricht The unintended consequences of dams and reservoirs
14.11.2018 | Uppsala University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Purdue cancer identity technology makes it easier to find a tumor's 'address'

16.11.2018 | Health and Medicine

Good preparation is half the digestion

16.11.2018 | Life Sciences

Microscope measures muscle weakness

16.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>