The Appalachians, which run for roughly 2,400 kilometres from Alabama to Newfoundland, were formed more than 300 million years ago when the North American and African continental plates collided.

The research team studied data collected by the Earthscope project, which uses GPS receivers and an array of portable seismometers to measure ground movement in northeastern USA. This was combined with data from the North American Gravity Database, allowing the researchers to determine the density of the rocks under and around the mountain range.

The results indicated the presence of a volcanic structure about 450 kilometres by 100 kilometres in size. The researchers were then able to use the data to model how the bend formed.

According to one of the study’s authors, Cindy Ebinger of the University of Rochester, scientists had previously known about the structure. ‘What we didn’t understand was the size of the structure or its implications for mountain-building processes,’ she said.

The computer model indicated that as the North American plate was pushed westward into the dense rock structure, it was folded and thrust upwards, creating the mountains. The shape of the structure caused the chain to shift east, forming the characteristic bend.