When an unstoppable force like the Indian subcontinent crashes into an immovable object like the Eurasian plate, the consequences include the tallest mountains in the world and a cadence of earthquakes like the magnitude 7.8 one that struck Nepal last month and a major aftershock in the same region last week.
Many of the geological questions about the collision remain unanswered. How did the Indian subcontinent get so quickly to where it is today? How big was India originally? Even the simplest of questions — when did India meet Eurasia, the tectonic plate that Europe and Asia sit on? — is up for debate, with researchers offering answers that differ by some 30 million years.
It seems that there are many puzzles about the details of the collision, and several inconvenient facts of involving the when, where, and what of the collision. In particular, it's not why the subcontinent is moving so fast, whether there were two or more subduction zones involved, and what has moved under Asia so far.