Earth cooled rapidly 13,000 years ago and the reason behind this is a series of volcanic eruptions which caused the average global temperature to drop by 3°C, a study claims.
It was previously believed that a meteorite impact was responsible, but a new study has found this to be incorrect.
Previous theories were based on geological findings which had incorrectly been attributed to rocks landing from space.
However, new analysis of the rock sediments shows they instead came from deep within Earth and were projected to the surface via violent eruptions.
The world-cooling period is known as the Younger Dryas and is associated with early human settlers and the extinction of the woolly mammoth.
Study co-author Professor Alan Brandon, of at the University of Houston, said: ‘This work shows that the geochemical signature associated with the cooling event is not unique but occurred four times between 9,000 and 15,000 years ago.
‘Thus, the trigger for this cooling event didn’t come from space.
‘Prior geochemical evidence for a large meteor exploding in the atmosphere instead reflects a period of major volcanic eruptions.’
Volcanic eruptions spread particles into the atmosphere, which reflect thermal energy from sunlight away from the surface.