Weathering and Erosion — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. A delta is a fan-shaped deposit of sediment at the mouth of a river.
Deltas form where rivers deposit sediment as they slow upon entering a larger body of water. Example: the Mississippi River Delta.
2. Wind picks up tiny particles of sand and blasts them against rocks in a process called abrasion.
Wind abrasion (sandblasting) slowly wears away rock surfaces as wind-driven particles scrape against them.
3. Plants help prevent erosion because their roots hold the soil in place.
Plant roots bind soil particles together, greatly reducing erosion by water and wind.
4. A U-shaped valley is formed by the slow movement of a glacier.
Glaciers erode valley walls and floors broadly as they move, producing characteristic U-shaped cross sections.
5. The Grand Canyon was carved over millions of years mainly by the Colorado River.
The Colorado River has been cutting through rock layers for about 5–6 million years, creating the Grand Canyon.
6. When ice melts and refreezes repeatedly, the process is called freeze-thaw weathering.
Freeze-thaw (frost wedging) cycles repeatedly expand and contract water in rock cracks, gradually breaking rocks apart.
7. The layer of broken rock and organic matter on Earth's surface is called soil.
Soil is formed from weathered rock particles mixed with organic matter (humus). It takes hundreds to thousands of years to form.
8. Waves deposit sand along the shore to form beaches.
Beaches form through deposition of sand and sediment by waves. They are in constant change due to ongoing erosion and deposition.
9. Rust forms on iron when it reacts with oxygen and water.
Iron + oxygen + water → iron oxide (rust). This is an example of oxidation, a type of chemical weathering.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
delta
→ fan-shaped river deposit
deep valley carved by a river
sand dune
→ hill of wind-deposited sand
hill of wind-deposited sand
moraine
→ ridge left by a glacier
fan-shaped river deposit
canyon
→ deep valley carved by a river
ridge left by a glacier
Delta → fan-shaped river deposit; sand dune → wind-deposited sand hill; moraine → ridge left by glacier; canyon → deep river-carved valley.