Unit 5 Lesson 4 How Does Earth’s Surface Change … 5 Lesson 4 How Does Earth’s Surface Change Quickly? Feel the Heat •As the lava cools, it gets hard. Some volcanoes grow larger

Unit 5 Lesson 4 How Does Earth’s Surface Change Quickly?

Copyright © Houghton Mifflin Harcourt Publishing Company

Earthquake!


Shaken Up

• An earthquake is a shaking of Earth’s surface that can cause land to rise and fall.


Earthquake!


Most earthquakes are too weak to be felt, but strong earthquakes can cause big changes to Earth’s surface.


Shaken Up

• Earthquakes happen because of movements in the Earth’s crust.

• They occur mostly in places where two pieces of crust meet.

• Pieces of crust push together, pull apart, or slide past each other.





Volcano!


Feel the Heat

• A volcano is a mountain made of cooled lava, ash, or other materials from eruptions.

• Like earthquakes, volcanoes are caused by movements of Earth’s crust.


Feel the Heat

• In some places, one piece of crust slides under another.

• This causes the rock underground to melt. This melted rock, called magma, moves upward.

• If it reaches an opening, it will erupt onto Earth’s surface. The melted rock is then called lava.



Feel the Heat

• As the lava cools, it gets hard. Some volcanoes grow larger with every eruption.

• In some volcanoes, lava gently oozes out. Other volcanoes explode!



Feel the Heat

• Lava, stone, and ash are thrown from the volcano’s opening with tremendous force. Exploding volcanoes can quickly change the Earth’s surface.



Feel the Heat



Feel the Heat



Big Changes


Fire, Water, Mud

• A forest fire starts small.

• It can be sparked by lightening, a bit of lava, or a careless person.

• It is important to act quickly to control forest fires.


Fire, Water, Mud

• Too much rain in a short period of time can cause a flood.

• A flood is a change that happens when streams, rivers, or lakes get too full and overflow.

• Entire towns can be destroyed. Over time, floodwater drains away, dries up, or is absorbed into the ground.



Fire, Water, Mud

• Sometimes, water from rain or a flood loosens dirt on the side of a hill or mountain.

• The dirt slides downhill in a mudslide or landslide.

• It may bury part of a town.



Fire, Water, Mud



Be Prepared


Planning Ahead

• How do you prepare for a disaster?

• You make an emergency plan and prepare your home.

• You make sure any pets will be safe, too!


Planning Ahead

• People do many things to prepare for disasters.

• Buildings are designed to withstand earthquakes. Rivers are built up to prevent floods.

• Emergency plans can help keep us safe. Families can talk about what to do in an emergency.





Unit 5 Lesson 4 How Does Earth’s Surface Change … 5 Lesson 4 How Does Earth’s Surface Change Quickly? Feel the Heat •As the lava cools, it gets hard. Some volcanoes grow larger

Documents

Unit 5 Lesson 4 How Does Earth’s Surface Change … 5 Lesson 4 How Does Earth’s Surface Change Quickly? Feel the Heat •As the lava cools, it gets hard. Some volcanoes grow larger