Wood from trees as high as the mountains can travel thousands of miles downriver to the Bay of Bengal as part of an ancient cycle that seems to be triggered by monsoons and other catastrophic events.

(Christian France-Lanord/Université de Lorraine)

At a Glance

Scientists found that fresh wood can travel from its mountain home to settle deep in the ocean.Thousands of miles from land, the trees and the carbon inside them are covered by sediments.The research suggests the trees may remove much more carbon than previously thought.

Trees knocked over by monsoons, floods or other catastrophes can be washed thousands of miles downstream and far out into the ocean.

There, the trees and the carbon inside them are covered by sediments that prevent the wood from decomposing and releasing greenhouse gases into the atmosphere.

That's according to in the Proceedings of the National Academy of Sciences.

Researchers drilled deep into sediment on the floor of the Bay of Bengal, 1,000 miles off the Bangladesh coast. When they examined the core samples from more than a half-mile down in the sediments, they found wood , according to a news release about the study.

(MORE: Warming Signs Podcast Explores How the Big Apple’s Taking a Bite Out of Carbon Emissions)

Many of the trees came from lowland sources, but one layer contained wood from trees that grew high in the mountains.

Scientists studying sediments in the Bay of Bengal found wood sediments dating back 19 million years that appear to be from trees high in the mountains – a sign that wood travels thousands of miles into the deep sea. Here is an aerial view of one leg of the river route.

(Christian France-Leonard/Université de Lorraine)

"We found pristine pieces of conifers. These trees grow two miles above sea level, up in the Himalayas," said team leader , who is also an associate professor of Earth sciences at the University of Southern California.

The researchers speculate that a natural dam, perhaps created by a glacier or landslide, collapsed about a million years ago and released a huge torrent of water. The surge carried the highland trees thousands of miles from Nepal through Bangladesh and into the Bengal Fan, the largest underwater sediment accumulation in the world.

The lowland trees were likely washed into the bay during monsoons or cyclones over the previous 19 million years.

The buried trees play an important role in the planet's carbon cycle, the researchers said. Usually, carbon inside a tree is released into the atmosphere through metabolism or when the tree is burned or decomposes. But a tree washed into the ocean carries its carbon to the seafloor, where it's entombed in sediment that prevents the tree from decomposing.

The amount of wood found in the Bay of Bengal suggests 50% more carbon may be buried than previously thought, the researchers found.

"As we've tried to calculate the amount of carbon in all parts of the carbon cycle, we didn't know about this forest of fragmented trees buried in the ocean floor," Feakins said. "Now we need to add it to the equation."