1. Changes to Earth’s Surface
Chapter 7
Changes to Earth’s Surface
This formation, near Hyden, Australia, looks like a tumbling wave. But what is it? From what material do you think it is made? How do you think it is formed?

2. Lesson 1
Water from melting glaciers cut through Earth’s crust to form the Upper St. Croix River gorge in Wisconsin about 10,000 years ago.

3. Mountains & Hills Mountains Hills Page 232
Earth’s surface looks flat from space. However, it is wrinkled cracked, and folded into many landforms. A landform is a natural feature on Earth’s surface.
Mountains are some of Earth’s most spectacular landforms. A mountain is an area that is higher than the land around it.
Hills look like mountains, but they are smaller.
Mountains form in many ways. Some mountains were volcanoes. Other mountains form when forces bend and fold Earth’s crust. Blocks of Earth’s crust can also get pushed upward to form mountains. It can take millions of years to form.
Mountains
Hills

4. Valleys & Canyons Page 233
You have learned that mountains are highlands. There are also lowland areas called valleys. A valley is an area with higher land around it. Valleys stretch between mountains and between hills.
There are different kinds of valleys. A canyon is a valley with steep walls.

5. Some plains are inland and others are along coasts.
Page 234
Some parts of Earth’s surface are mostly flat. These large, flat landforms are called plains.
Some plains are inland and others are along coasts.
A plateau is also a flat area, but it is higher than the land around it. The edges of plateaus can form steep cliffs.
Plains & Plateaus

6. More on Plateaus…
Page 234
As plateaus erode, they can become other landforms. A much smaller landform with the shape of a plateau is a mesa. A smaller mesa is a butte. These landforms sometimes make unusual topography.
Topography is the shape of landforms in an area.

7. Page 235
Deltas & Dunes
Deltas and dunes look very different, but both are formed by the movement of sand and sediment.
Deltas form at the ends of rivers. Fast-moving rivers carry away bits of soil and rock. When a river enters a lake or an ocean, it slows down. When this happens, the water can’t carry as much material. It drops most of the rock and soil where it meets the lake or ocean, forming a delta.
Dunes form in dry areas or along sandy coasts. They form where wind carries sand. As the wind flows over rocks or other barriers, its speed slows. The wind drops sand around the object. Over time, a dune forms.

8. Islands
Page 236
Every island is a body of land surrounded by water. Islands differ in the way they form. Some were once linked to a mainland. When the sea level rose thousands of years ago, water covered the land that formed the link.
Other islands are the tops of volcanoes that have been built up from the sea floor.
Coral islands form from the remains of tiny sea animals. The remains form huge structures of limestone in the sea. There are many coral islands in the Pacific Ocean.

9. Landforms Slideshow

10. List 2 facts for each landform:
Mountains
Hills
Valleys
Canyons
Plains
Plateaus
Deltas
Dunes
Islands