STEVE INSKEEP, HOST: Next we have the underlying cause of a disaster.</s>RENEE MONTAGNE, HOST: It's a look at plate tectonics, the movements of the Earth's crust that caused last weekend's earthquake in Nepal.</s>STEVE INSKEEP, HOST: We learn in school that the crust of the earth is divided into huge plates that drift apart or collide. The immense Himalayas were made by an especially dramatic collision.</s>KERRY SIEH: Basically India is now sliding beneath the Himalaya and beneath Tibet.</s>RENEE MONTAGNE, HOST: Kerry Sieh is director of the Earth Observatory of Singapore. He explained how this all got started. India used to be an island. Then, about 50 million years ago, it crashed into the rest of Asia.</s>KERRY SIEH: That collision produced the Himalayas. It's produced big earthquake faults in Tibet and in eastern China.</s>STEVE INSKEEP, HOST: A sudden movement along those faults is what we call an earthquake, like the one last weekend, as well as others that killed tens of thousands of people in Pakistan and China a few years ago. Another earthquake in Nepal back in 1934 was even bigger than the latest disaster.</s>RENEE MONTAGNE, HOST: All according to Sieh because one of those two tectonic plates is still slipping under the other.</s>KERRY SIEH: It has frictional resistance like two pieces of sandpaper against each other. But after you push enough, it finally decides, I can't stand this anymore, and it suddenly slips.</s>RENEE MONTAGNE, HOST: And, he says, this quake could point to others ahead.</s>KERRY SIEH: We're concerned that the areas to the east and to the west of this and also further south are ready to break.</s>STEVE INSKEEP, HOST: The problem of course is knowing when. As Sieh puts it, it could be tomorrow; it could also be 100 years from now.
The earthquake that struck Nepal over the weekend was hardly a surprise. Geologists have known for decades that tectonic plates underneath Nepal were capable of creating a devastating earthquake.