Chapter 4, Section 1 Landforms (part 2) Focus Questions… (continued from part 1) 2. What physical processes on Earth’s surface wear down the land? 3. How do these physical processes interact to create landforms?

Weathering breaks rocks into smaller particles of gravel, sand, and mud The first step in the formation of soil; it happens very slowly

Two kinds of weathering Chemical weathering – water slowly dissolves certain rocks

Physical weathering – some forces cause rocks to crack, other forces pry rocks apart; also called mechanical weathering

Erosion wears away the rocks and transports them downhill Water - is the most powerful force of erosion

Wind Has its greatest effect where there are few plants, usually due to a dry climate Why? Wears down hard rocks by blowing particles of sand against them (like sandblasting)

Ice Glaciers Gravity pulls them downhill Are large accumulations of snow and ice that move slowly over the land Gravity pulls them downhill Have the power to remove anything in their path

Glaciers around the world are melting – why is this happening?

Once the rocks are broken down and carried away, it’s time for the third step in the process: Deposition These particles of sand, mud, and silt eventually find their way to the bottom of the ocean and become sedimentary rocks.

Landforms We can classify landforms based on how they were formed.

1. Landforms made by tectonic processes Created by volcanoes, folding and faulting Himalayas – highest mountains on earth Death Valley – deep basin, below sea level Mariana Trench – deepest part of the ocean

More Tectonic Landforms

2. Landforms made by erosion These are made of rock, with a thin layer of weathered sediments and soil at the surface Surface is being slowly worn down by erosion Harder rocks wear away more slowly Examples - valleys, plains, plateaus

3. Landforms made of sediments deposited by wind, water, or ice Deposited by wind – sand dunes Deposited by water – flood plain Deposited by ice – glacial moraine

Weathering and Erosion Weathering Erosion Physical Processes • Heating and cooling • Freezing and thawing • Tree roots Chemical Processes • Substances in air and water Water • Rainfall • Rivers • Waves Wind • Abrasion • Move from one place to another Ice • Glaciers