Untitled Quiz

Grade 8 Changing Earth's Surface - Chapter 3 Section 2

•  The processes that slowly break down mountains are often not noticeable during a person's lifetime.
• Copy notes into notebook, leaving space for additions.
• Answer review questions using the textbook if needed.
• Watch videos, noting any interesting information. You can adjust playback speed.

Essential Questions

• What is the difference between physical and chemical weathering?
• How do water, ice, and wind shape Earth's surface?

Breaking Down Earth Materials

• Processes breaking down mountains are called weathering.
• Weathering involves mechanical and chemical processes.
• The material formed from broken rocks is sediment.
• Sediment can take forms like rock fragments, sand, silt, and clay.

Types of Sediment

•  Sediment types are determined by texture, composition, and history of transport, intensity of weathering, and source rock properties.

Physical Weathering

• Physical weathering breaks down rocks without changing their composition.
• Examples include: plate movements, boulders rolling off cliffs, cracks in rocks widening by repeated freezing and thawing of water, plant roots prying open rocks (root pry).

Chemical Weathering

• Chemical weathering alters the rock's composition.
• Examples include: minerals dissolving in slightly acidic water (like rainwater), other minerals reacting with carbon dioxide or oxygen in the air.
• Abundant water and warmer temperatures speed up chemical weathering.

Moving Earth Materials

• Erosion is the movement of weathered material (sediment) from one location to another.
• Deposition is the laying down or settling of eroded material.
• Mass wasting is downhill movement of rocks or soil due to gravity.
• A landslide is a type of mass wasting on steep slopes.
• Water, wind, ice, and gravity move sediment.
• Faster water moves larger pieces of sediment than slower water.
• Sediment is deposited on the sides of rivers as water slows.
• Rivers entering oceans/lakes deposit sediment to form deltas.
• Wind erosion is important in deserts, creating landforms like sand dunes and ripples.

Ice

• Glaciers are large masses of ice that move slowly across Earth's surface.
• Gravity causes glaciers to flow downhill, weathering the rocks beneath.
• Glaciers pick up sediment as they flow and deposit it when they melt.
• Examples include moraines.

Glaciers and Cape Cod

• Glaciers affected the landscape by erosion and deposition, shaping the areas they covered

What about Yosemite?

• Yosemite's landscape was affected by glaciers

Plate Tectonics

• Plate tectonics explains many Earth surface features and the processes that occur on it.

Climate

• Climate affects the processes that move Earth material.

Review Questions

• How is weathering related to sediment?
• What processes break rock into smaller pieces?
• What are the differences between chemical and physical weathering?
• What forces cause rock to move downhill?
• What causes most erosion on Earth?