Another view speculates that the Storegga tsunami devastated Doggerland, but then ebbed back into the sea, and that later Lake Agassiz (in North America) burst, releasing so much fresh water that sea levels rose over about two years to flood much of Doggerland and make Great Britain an island.[14] The difference in distribution of broken shells between lower-lying and high-lying parts of the area also suggest survival of land after the Storegga tsunami.[15]