Featured Research

from universities, journals, and other organizations

Rise In Sea Level, Loss Of Wet Lands May Account For Unstable Ground In Mississippi Delta

Date:
July 21, 2006
Source:
National Science Foundation
Summary:
While erosion and wetland loss have become huge problems along Louisiana's coast, the land 30 to 50 feet beneath much of the Mississippi Delta has been very stable for the past 8,000 years, with low to nonexistent subsidence rates. So say geoscientists from Tulane University and Utrecht University in the Netherlands, challenging the notion that subsidence, or sinking of the earth, bears much of the blame for Louisiana's coastal geology problems.

Over thousands of years, the thick, muddy delta deposit compacts under its own weight, squeezing water out. As a result, sea level rises and covers the wetlands.
Credit: Zina Deretsky, National Science Foundation

While erosion and wetland loss have become huge problems along Louisiana's coast, the land 30 to 50 feet beneath much of the Mississippi Delta has been very stable for the past 8,000 years, with low to nonexistent subsidence rates. So say geoscientists from Tulane University and Utrecht University in the Netherlands, challenging the notion that subsidence, or sinking of the earth, bears much of the blame for Louisiana's coastal geology problems.

A research team led by Tulane's Torbjörn Törnqvist suggests instead that compaction of the shallowest and most-recently formed delta sediments is the main cause of subsidence in that area.

"Our research could have major implications for rebuilding plans that are currently being debated," said Tornqvist. "Over the long term, comprehensive understanding of subsidence will better support rational coastal management and successful urban and land-use planning for all low-lying areas along the Gulf Coast."

Their findings were published online on Fri., July 21, 2006, in the journal Geology, published by the Geological Society of America.

Törnqvist and his team reconstructed the rate of sea-level rise over the past 8,000 years from three separate areas in the Mississippi Delta. Peat samples were used as sea-level indicators because peat forms as soon as water levels rise above the land surface.

"If we are to reverse the loss of Louisiana wetlands and the protection they afford New Orleans, we need to think outside the box," said H. Richard Lane, program director in the National Science Foundation's Division of Earth Sciences, which funded the research. "Innovative research such as this opens up new possibilities for addressing environmental issues."

According to Törnqvist, rapid subsidence of coastal Louisiana is well documented but not well understood. Leading candidates include:

* Long-term subsidence and faulting of the Earth's crust caused by rapidly accumulating sediments in the Mississippi Delta
* Compaction of relatively shallow and water-rich deposits formed during the past 10,000 years
* Withdrawal of oil, gas and groundwater from the subsurface

The role of tectonic processes and their relationship to sea-level rise, coastal erosion and wetland loss have received considerable attention from researchers. But, "if that were the whole story, there would be major consequences for Louisiana, because subsidence of Earth's crust is a natural process that remains beyond human control," said Törnqvist.

Carbon isotope analyses verified that rise in sea level directly controlled accumulation of sediment. Elevation of sampling sites was determined by a combination of GPS measurements and optical surveying. The team then compared its results with sea-level data from the same time period from areas in the Caribbean regarded as tectonically stable, including Florida and the Bahamas.

The geologists were surprised to find no difference, suggesting that large portions of the Mississippi Delta's basement land is stable. They also inferred from the data that long-term subsidence rates are a fraction of a millimeter per year rather than 10 millimeters, as had been thought.

Törnqvist points out that these numbers do not necessarily apply to the entire delta. He also notes that well-documented high-subsidence rates in and near the lower "bird foot" of the delta--so named because the waterways form the shape of a bird's foot--indicate that different conditions prevail there.

"It remains to be demonstrated how rapidly the basement under metropolitan New Orleans subsides," he said.


Story Source:

The above story is based on materials provided by National Science Foundation. Note: Materials may be edited for content and length.


Cite This Page:

National Science Foundation. "Rise In Sea Level, Loss Of Wet Lands May Account For Unstable Ground In Mississippi Delta." ScienceDaily. ScienceDaily, 21 July 2006. <www.sciencedaily.com/releases/2006/07/060721115459.htm>.
National Science Foundation. (2006, July 21). Rise In Sea Level, Loss Of Wet Lands May Account For Unstable Ground In Mississippi Delta. ScienceDaily. Retrieved September 22, 2014 from www.sciencedaily.com/releases/2006/07/060721115459.htm
National Science Foundation. "Rise In Sea Level, Loss Of Wet Lands May Account For Unstable Ground In Mississippi Delta." ScienceDaily. www.sciencedaily.com/releases/2006/07/060721115459.htm (accessed September 22, 2014).

Share This



More Earth & Climate News

Monday, September 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Hundreds of Thousands Hit NYC Streets to Protest Climate Change

Hundreds of Thousands Hit NYC Streets to Protest Climate Change

AFP (Sep. 22, 2014) — Celebrities, political leaders and the masses rallied in New York and across the globe demanding urgent action on climate change, with organizers saying 600,000 people hit the streets. Duration: 01:19 Video provided by AFP
Powered by NewsLook.com
Inside London's Massive Sewer Tunnel Project

Inside London's Massive Sewer Tunnel Project

AP (Sep. 22, 2014) — Billions of dollars are being spent on a massive super sewer to take away London's vast output of waste, which is endangering the River Thames. (Sept. 22) Video provided by AP
Powered by NewsLook.com
Washed-Up 'Alien Hairballs' Are Actually Algae

Washed-Up 'Alien Hairballs' Are Actually Algae

Newsy (Sep. 22, 2014) — Green balls of algae washed up on Sydney, Australia's Dee Why Beach. Video provided by Newsy
Powered by NewsLook.com
Was The Biggest Climate March In History Underreported?

Was The Biggest Climate March In History Underreported?

Newsy (Sep. 22, 2014) — The People's Climate March in New York City drew more than 300,000 people, possibly a record-breaking number. Was the march underreported? Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins