University of Wisconsin-Madison researchers have found deep underground soils to be rich in carbon content.

Researchers said that soil erosion, farming, deforestation and mining among others can disturb and uncover these soil formations. As a result of human activities, carbon that had been sealed away for thousands of years in arid and semi-arid environments is more likely to be reintroduced to the environment that can further contribute to global climate change.

"There is a lot of carbon at depths where nobody is measuring," said Erika Marin-Spiotta, an assistant professor of geography and the lead author of the study, in a press release. "It was assumed that there was little carbon in deeper soils. Most studies are done in only the top 30 centimeters. Our study is showing that we are potentially grossly underestimating carbon in soils."

For the study, the researchers examined Brady soil, formed between 15,000 and 13,500 years ago, in Nebraska, Kansas, and other parts of the Great Plains. The soil is located six-and-a- half meters below the surface. It was buried by accumulation of windblown dust known as loess after glaciers covering North America started to retreat some 10,000 years ago.

When the glaciers began to recede, the area where the Brady soil formed underwent radical change including vegetation and wildfire that contributed to carbon sequestration. And the loess rapidly buried the soil.

Marin-Spiotta said that most of Brady soil is black carbon and was the result of wildfires.

Such buried soils are not only exclusive to the Great Plains and that it takes place worldwide.

The team employed new analytical methods, including spectroscopic and isotopic analyses, to examine the soil and its chemistry. The researchers said that rapid burial of Brady soil prevented them from undergoing biological processes that would have normally dissolved carbon in the soil.

Researchers said that Brady soil can be considered as a time capsule of a past environment. It provides environmentalists an insight into how the environment endured various climate shifts.

"The world was getting warmer during the time the Brady soil formed," said Mason. "Warm-season prairie grasses were increasing and their expansion on the landscape was almost certainly related to rising temperatures."

The findings are published in the journal Nature Geoscience.