In the process of rock movement, the ground will vibrate, that is, an earthquake will occur. When hot magma rushes out of the ground along cracks in the earth's crust, it is called volcanic eruption. A volcano is a highland formed by the accumulation of materials erupting from a crater. Earthquakes and volcanic activities can change the shape of the ground in a short time. "Hundreds of rivers boiled and mounds collapsed. The high shore is a valley, and the deep valley is a mausoleum "is the earthquake site."

So choose: a.