Ancient Underwater Forests In Gulf Of Mexico

Ancient Underwater Forests In Gulf Of Mexico

This article was prepared for Woods Reader Magazine

A long, long time ago (over 50,000 years) during the last great ice age, the coastline along the Gulf of Mexico was more than 10 miles farther out to sea than it is today. At that time the coastal areas weren’t that much different than they are now…swampy, with rivers and streams, and trees like palms and bald cypress (taxodium distichum). 

In the millennia since, sea level has risen by as much as 80 feet to its present formation. But there are still remnants of the old coast, now submerged underwater.

shoreline graphicScientists have just begun exploring the old coastline, after sports divers reported finding stumps of prehistoric trees in the depths of the Gulf, off the coast of Alabama. It is believed Hurricane Ivan in 2004 scraped away layers of mud and sand to expose the stumps.

Ben Raines, at the time a writer for the Mobile, Alabama, newspaper was one of the first to dive on the site. “I was stunned…I knew this was a huge deal, and we needed to call in the scientists.” 

Scientists soon followed to begin documenting the underwater forest. One of them was Grant Harley, a dendrochronologist, specializing in studying tree rings. He is now an Associate Professor at the University of Idaho, but at the time of the forest discovery he was at Southern Mississippi University. 

“We were kinda surprised” at the age of the tree stumps, Harley says. They brought up samples from the depths that are older than the limitations of carbon dating, which is 50,000 years. The scientists turned to studying the layers of sediment on the Gulf floor to try and get an accurate guess at the tree’s ages. They concluded the forest goes back 65,000-75,000 years ago. 

Harley sawed through some of the old trunks to study their rings. What he found shocked him.

“I sanded them down to study the rings, and you could still smell the resin from the tree”, a tree that was 70,000 years old. Harley calls the tree rings “a bar code” that identifies the life of the tree. 

fish swim in forest
Photo by Ben Raines

The tree forests are home to large masses of fish. Divers and sport fishers along the Florida Gulf coast have long told the stories of great fishing and diving found far offshore among the remnants of the ancient coastline. But it wasn’t until the Alabama discovery that the scientific research began.

According to Harley, it appears the trees all died about the same time, during a period of rapid  sea level rise. Kristene DeLong, a paleoclimatologist and professor of Geography and Anthropology at LSU was part of the study team. She dates the trees and coastal environment at that time to the Pleistocene Era, which was the last great ice age. She estimates at that time there was a 10-30 foot sea level rise in a one thousand year time span. “A thousand years is a short time, geologically speaking”, she says. 

Scientists are studying the first trees found off Alabama’s coast, but there are plenty more sites around the Gulf. There are so many sites that they are posing a problem for energy exploration. “Drillers were accidentally drilling into the tree stumps and it would clog their equipment”, Harley says.

The scientific team is now working with the Bureau of Energy Management to identify sites safe for drilling.

DeLong says a second phase of the study is about to begin. It will include bringing in a larger ship with 3-D imaging equipment to find more of the wood under the floor of the Gulf. She hopes to find pollen and seeds in the sediment that could further identify the era of the forest.

She says the coastal areas back then were very similar to what we have today, except without mangroves. “It was too cold for mangroves” during that era, she notes. 

Ben Raines says the site gave him “the most graphic demonstration of climate change I have ever seen…it gives you an intense understanding of sea level change.”

There is also an effort in Congress to have the area of the Gulf designated as a National Marine Sanctuary, to protect the forest. 

Bald cypress trees can grow to over 100 feet tall, and live over a thousand years. They like growing in water, or well drained soil, but can tolerate drier soils. They can’t survive salt water. Their trunk is often surrounded by cypress “knees” that grow upward out of the water. They are known for their bright rustic red coloring in the fall.

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