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 Torbjrn Trnqvist 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.

Trnqvist 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 Trnqvist, 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 accumul
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Contact: Cheryl Dybas
cdybas@nsf.gov
703-292-7734
National Science Foundation
21-Jul-2006