Ben Nevis caldera part 1

Last Christmas we went up Mount Teide on Tenerife. Many years ago, the then top of the volcano collapsed inwards creating a vast bowl, It's a pretty flat circle surrounded by cliffs. This is called a caldera.Then we went to Ben Nevis and found this:

So the same thing happened to Ben Nevis 410 million years ago. This is going to take some thinking about. But the view below must once have looked like the top picture from Tenerife!