Ch. 11: Weathering and Erosion Vocabulary: landform, weathering, erosion, glacier, deposition, sediment, delta

Weathering Most landforms are made of rock. Rock is very hard, but can be broken down by wind and water. This process is called weathering. Sand blows across rocks and eats away at its surface. Rainwater gets into cracks in rocks, then freezes; expanding and cracking the rocks into pieces. Rocks located in rivers or underwater are smoothed by currents that flow through the water running over them. Weathering is a process that takes thousands of years.

Erosion and Deposition When weathering breaks rocks into pieces, some of those pieces stay where they are, but some of them get moved by the wind or water. Erosion is when rocks and dirt gets picked up and moved. Deposition is when rocks and dirt get dropped backed down.

Erosion and Deposition Erosion and deposition are caused my many sources. Rivers pick up rocks and dirt as they flow by. Glaciers pick up large rocks, then melt leaving them standing in fields. Sandstorms pick up large amounts of sand and move it from one area to another, reshaping whole deserts. The dirt and rocks that get left behind are called sediment.

Reshaping the Earth’s Surface Look at how much closer to the rocks Niagra falls was 100 years ago.

Reshaping the Earth’s Surface Another major way the Earth is reshaped is around river deltas. A delta is an area at the end of a river where dirt and mud are deposited forming forks in the waterway before you reach the ocean. A delta is usually shaped like a triangular fan. The Amazon River Delta

Questions About Chapter 11 1.When a glacier melts and leaves a pile rocks, this process is called? 2.Define the word weathering. 3.Which part of the natural earth-moving process involves the actual picking up and moving of weathered rock? 4.Which landforms develop near the mouth of a river? 5.What are the two main causes of weathering?