Ch. 9Lesson 3

How can Earth’s surface change

rapidly?

• forms @ weak spot in Earth’s crust where magma is forced up & reaches surface

• causes rapid changes

volcano

ashcrater

Mount St Helens

Before After

will not erupt again

extinct

has frequent eruptions or shows signs of future eruptions

active

Has not erupted for a long time (sleeping)

dormant

4 layers of Earth

outer layer

of rock

plates•large pieces that Earth’s crust is divided into

•constantly moving

fault•break in Earth’s crust

earthquake•sudden movement that causes Earth’s crust to shake

•San Andreas fault in Calif.- many earthquakes

San Francisco earthquake of 1906

focus= place underground where plates start to move- where earthquake begins

epicenter= place on Earth’s surface above focus

huge ocean wave created by an earthquake or volcano