What was Doggerland, and how did an entire country vanish beneath the North Sea?

The answer

Doggerland was a vast landmass connecting Great Britain to continental Europe during the last Ice Age, when sea levels were up to 120 meters lower than today. At its peak around 10,000 BCE, it was a rich landscape of hills, rivers, marshes, and forests inhabited by Mesolithic hunter-gatherers. As glaciers melted, the land gradually flooded, but the final blow came around 6200 BCE when the Storegga Slides - massive underwater landslides off the coast of Norway - generated a tsunami with waves up to 25 meters high, devastating the remaining low-lying areas. Fishing trawlers regularly dredge up Doggerland artifacts including mammoth bones, flint tools, and even a Neanderthal skull fragment from the North Sea floor.