In 2014, scientists released a study documenting 570 locations on the floor of the Atlantic Ocean where methane was leaking. Bubbly, gurgling trails, these leaks, produced by microbes, were found at depths between 800 and 2,000 feet.

Now, scientists publishing in the Journal of Geophysical Research—Biogeosciences have discovered this process isn’t unique to the ocean. In fact, they found it occurring in freshwater springs in California.

The ocean floor process is known as serpentinization, wherein water and rock, in a chemical reaction, produce a green stone known as serpentine. According to the American Geophysical Union, The Cedars, in Sonoma County, is an easily accessible place where the process is known to occur on land. As a result of the process, byproducts, like methane, hydrogen, and heat, are produced.

“While geochemical data indicate that methane at most sites of present-day serpentinization is abiogenic, the stable carbon, hydrogen, and clumped isotope data as well as the hydrocarbon gas composition from The Cedars … are consistent with a microbial origin for methane,” the researchers wrote.

In their study, the researchers brought water samples back to the laboratory for testing in a variety of environments. Compared against the samples with dead microbes, the samples containing live microbes produced much more methane, up to 650 percent more in some cases.

This suggests the methane in The Cedars is produced by microbes.

Additionally, the researchers found the microbes might be responsible for converting carbon dioxide into methane. According to the American Geophysical Union, this could be a blow to those who want to use sites like The Cedars as a place for carbon sequestration.

According to astrobiologist William Brazelton, of the University of Utah in Salt Lake City, this new study may help illustrate how microbes survived on a primordial Earth. Also, methane signatures in the Martian atmosphere may be markers of microbial life, said Brazelton, who was not involved in the study.