Geologists from Colby College in Waterville, Maine, have tracked the oldest wildfires that lit between short plants and seasonal plants that reach a person's knee or waist length.

These fires were discovered by analyzing 430 million-year-old coal deposits examined in Wales and Poland.

Plant fuels for starting fires

In a report published on Science Alert, paleobotanist Ian Glaspool of Colby College says, "It now appears as if our evidence of fire matches closely with our evidence of the oldest large fossils of Earth's plants."

He added that "the presence of fuel - in the form of large plant fossils in the weakest case - greatly increases the likelihood of forest fires."

Forest fires need fuel such as plants, an ignition source such as lightning strikes, and enough oxygen to complete the combustion process.

In their study, which was published in the journal Geology on June 13, the researchers wrote that the fires were able to spread, leaving coal deposits.

One of the samples used in the study (Glasspool et al. - Journal of Geology)

"There had to be enough vegetation in the Silurian period for wildfires to spread and to leave a record of those massive fires," said paleontologist Robert Gastaldo of Colby College.

The Silurian era is defined as the shortest geological period of the Paleozoic Era, which lasted 24.6 million years from the end of the Ordovician Period to the beginning of the Devonian Period.

The Silurian is the first period to contain the fossils of extensive non-microscopic life on Earth.

According to the study, the landscapes of Europe we know today are significantly different from what they were hundreds of millions of years ago, and the two sites the researchers used for their analysis were in the ancient continents of Avalonia and Baltica at the time of these wildfires.

Change in the proportion of oxygen and carbon in the atmosphere

As is the case today, wildfires contributed significantly to the carbon and phosphorous cycles as well, and to the movement of sediments over the Earth's surface.

"For a long time, forest fires have been an integral part of Earth system processes, and their role in these processes has almost certainly been underestimated," says Glaspool.

Forest fires have historically contributed significantly to the carbon and phosphorous cycles (Shutterstock)

The researchers also reported that oxygen levels in the Earth's atmosphere were at least 16% at the time.

Although the level of oxygen in the atmosphere has reached 21% today, it has changed a great deal during Earth's history.

The results of the team's analyzes showed that oxygen levels in the atmosphere 430 million years ago were probably 21% or higher.

Thus, the results presented by this research paper break the previous record for the oldest recorded wildfire with a difference of 10 million years, and it also highlights the importance of research in forest fires to trace the history of the Earth and chart its topography.