I Didn’t Know That . . .

Q: What would happen if all movement of Earth’s tectonic plates--the large land masses floating on the planet’s molten interior--stopped?

A: Earth would become a very different place, according to seismologist Kerry Sieh of Caltech, although it might take a long time for some effects to become apparent. Of immediate interest to Angelenos, there would be far fewer earthquakes because most of them are caused by stresses resulting from plate movements. The volcanoes of the Pacific “Ring of Fire” would all shut down, and the steady southeastern movement of volcanic activity along the Hawaiian Islands would also stop. New mountains would no longer be formed, and erosion from wind and rain would eventually level those now in existence, so Earth’s surface would become much flatter. Finally, the motion of tectonic plates absorbs some of Earth’s internal heat. If the plates stopped moving, Sieh said, the planet would have to find a new and efficient way to blow off that heat, and it is not clear what it would be.