London: Hot rock flowing under the Earth`s crust caused Scotland`s coastline to rise and fall by hundreds of metres some 55 million years ago, according to a new study.
Global sea levels can change by more than 100 metres in only tens of thousands of years as land ice accumulates or melts. Now according to Bryan Lovell of the University of Cambridge and colleagues, evidence from Scotland reveals that changes in the Earth`s mantle may produce similarly dramatic changes in local sea levels, although on a slightly longer timescale.
The researchers have accumulated measurements from oil well cores and seismic imaging around the coast of Scotland.
These demonstrate that 55 million years ago, the western flank rose and fell by at least 490 metres within 2 million years or so.
A similar event seems to have occurred about a million years later on the eastern flank.
The team suggests that a pulse of hot, solid rock rose from a hotspot beneath Iceland and travelled east beneath the Earth`s crust.
Since the pulse was hotter than surrounding rock, it had a greater volume, lifting the land it passed under it.
"It`s as though a giant hand pushed the surface up and then after a while pulled it down again," The New Scientist quoted Lovell, as saying.
The study appears in the Journal of the Geological Society.