Britain: only recently an island
A great part of Britain's identity is wrapped up in the fact that it's a part of Europe, but it stands apart, quite literally, as an island. According to new sonar studies of the Channel which runs between Britain and France, that wasn't always the case. Until about 200,000 years ago, Britain was a peninsula of Europe, and could be walked to from mainland France -- as many early humans did. So what severed the soil? An almost unimaginably huge flood, possibly triggered by a small earthquake, pushed a giant, river-fed lake through the narrow isthmus which once stood where the English Channel now flows; then, the proverbial dam broke. At its peak, the flood may have discharged up to a million cubic meters of water per second, making it one of the most significant known megafloods in the Earth's history.
To Pacific Northwesterners in the know, this may sound a bit familiar: the beautiful Columbia River Gorge which separates Oregon and Washington wasn't there a few hundred thousand years ago, either. The end of an ice age sent huge amounts of rocky glacier meltwater cascading (no pun intended) from eastern Washington toward the sea, and with it, it took some really significant chunks of what was then simply the Cascade mountain range. Which is why the Gorge boasts some of the highest and most impressive waterfalls in the country; until that precipitous flood, those were rivers flowing through a more or less uninterrupted mountain range! At its height, the waters were over 1,000 feet deep, moved at more than 90 miles per hour and carrying house-sized boulders. Perfect for a little x-treme tubing, ice age style.