Saturday's terrible earthquake was the latest result of an ongoing collision of giant pieces of our planet, a slow-moving disaster that started about 50 million years ago.
April 27, 2015
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Between 55 million and 40 million years ago, the northern edge of what is now India began to slam into the giant slab of Earth's crust that today carries Nepal and Tibet. This ancient collision had a terrible after-effect this past Saturday: The which had an estimated death toll of as of Monday evening.
India bulled its way under Nepal those many millions of years ago, shoving the northern land skyward. That move began to create the towering Himalaya, including Mt. Everest. The collision is still going on, as India moves several centimeters north each year, and this has created an unstable fissure in the planet's crust, known as the Himalayan frontal thrust fault. This boundary zone, shown below, continues to release enormous earthquakes. Saturday's magnitude 7.8 disaster that released a 8.1 magnitude quake in 1934, according to Susan Hough, a seismologist with the U.S. Geological Survey in Pasadena, California. That quake killed an .
Here are illustrations that show, first, how the initial collision occured, then how the thrust fault is continuing to fracture the crust in the area, and finally where the frontal thrust fault lies in relation to other cracks in this very quake-prone zone.
The Structure of Mountain Ranges," by Peter Molnar, in Scientific American, July 1986; Illustration by Ian Worpole]
Climate and the Evolution of Mountains," By Kip Hodges, in Scientific American, August 2006; Graphic by Jen Christiansen; Source: “Southward Extrusion of Tibetan Crust and its Effect on Himalayan Tectonics," By K. V. Hodges, J. M. Hurtado and K. X. Whipple, in Tectonics, VOL . 20, NO. 6 , pages 799–809; 2001].The Collision between India and Eurasia," By Peter Molnar and Paul Tapponnier, Scientific American, April 1977; Graphic by Andrew Tomko].
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