The ground we stand on seems permanent and unchanging, but the rocks that make up Earth’s crust are actually subject to a cycle of birth and death that changes our planet’s surface over eons. Now scientists have found evidence that this cycle is quicker than thought: 500 million years instead of 2 billion.

The tectonic plates that make up Earth’s crust are constantly jostling against each other: brushing past one another in some places, moving apart in other areas, and butting head-on in still other places.

Where these head-on collisions occur, denser oceanic crust is shoved beneath lighter continental crust, causing it to melt in the ferocious temperatures and pressures of Earth’s mantle. This oceanic crust gets mixed into the rest of the mantle, which because of its high temperature and pressure slowly flows and fuels the world’s volcanoes.