Then,seventy-million years ago, the Earth's surface, or crust,pushed upward.

VOA: special.2010.01.04

"It's a horizontal motion of two pieces of the Earth's crust on either side of a vertical crack in the Earth,"

VOA: standard.2010.01.13

Earthquakes generally occur when the tectonic plates that make up the Earth's crust move suddenly.

VOA: standard.2010.01.13