North America Moves About as Fast as Fingernails Grow

The ground feels fixed, but it is on the move. NASA explains that Earth’s lithosphere, which includes the crust and the upper mantle, is divided into huge plates that are constantly moving. For example, the North American plate moves west over the Pacific Ocean basin, roughly at a rate equal to the growth of our fingernails. Slow as that is, it shapes the planet. According to NASA, earthquakes result when plates grind past one another, ride up over one another, collide to make mountains, or split and separate. The plates are the top of a layered planet. NASA describes Earth as having four main layers: an inner core at the center, then the outer core, the mantle and the crust. On land the crust goes about 19 miles deep on average.