I was looking at the geology subreddit the other day and someone asked an intriguing question: why aren't the Himalayas volcanic? They are the largest mountains on the planet and span thousands of miles but nary a volcano can be found. This might seem strange to many people as there are mountain ranges that are full of volcanoes -- the Andes and the Cascades for example. Why are they different?
What it boils down to is the different ways the Earth's tectonic plates interact. Sometimes when they collide, you just build big mountains and other times you get mountains and volcanoes.
