By Kara Scannell
(CNN) — An ancient fire used thousands of years ago to keep warm and protect itself against ice is still burning and is the size of modern skyscrapers, a research team told CNN.
A 2,500-year-old fire has been detected beneath the glaciers of Lake Superior, according to a team of researchers from the University of Michigan, who were investigating how prehistoric forests may have responded to climate change and changes in weather patterns.
The Lake Superior shoreline in Michigan serves as a natural heat source for thousands of years and the researchers had been poring over paleontological and archaeological finds to gain a better understanding of the fire-bearing environment at that time.
After sifting through more than 35,000 prehistoric stone and ivory artifacts collected at the shoreline, the team realized that they were likely finding a spear point, a spear tip found in the forest, where it had been used to kill and slice the wood of an ancient oak tree.
Then, carbon dating showed the projectile point was dated to the second millennium B.C. Some 800 years earlier than a second spear point from the ancient American town of Ann Arbor found nearby, the researcher said.
What made the new find different, and what eventually convinced them that it could be an ancient fire, was the heat in the whole circle.
The 1,300-square-meter fire was at around 950 degrees Fahrenheit and could still be burning, said a team member, Rick Kurth, who is the deputy director of the University of Michigan’s Max Planck Institute for Meteorology.
The fire was still big enough that it covered an area the size of a modern-day city’s fifth floor, he said.
Researchers believe the ancient fire was first discovered over 150 years ago and even filled an entire warehouse with melted remnants of oak and in the process of preservation caused 70 percent of the wood to release its toxins.
It is not yet clear what caused the fire, though it could have been as simple as a huge firestorm, from melting sea ice, or a massive lightning strike, particularly in warmer climates, cutting down trees and creating dry, burning ground, which could have spread to the sea ice.
“We really don’t know,” Kurth said. “But the fact that we have so many interesting fires and that one has at least 3,000 years of history on it is giving us a chance to learn more.”