Plate tectonics is the theory that Earth's outer layer is made up of plates, which have moved throughout Earth's history. The theory explains the how and why behind mountains, volcanoes ...

According to plate tectonics theory, Earth's outer shell is divided into multiple plates that slowly glide over the mantle. This slowly changes Earth's surface over time by merging, or separating ...

The tiny Juan de Fuca plate is largely responsible for the volcanoes ... The movement of the plates creates three types of tectonic boundaries: convergent, where plates move into one another ...

Both are twice the size of the moon. Those blobs, the theory goes, created plate tectonics – the geologic phenomenon that fuels earthquakes and volcanoes, which allow life to flourish.