Science Chapter 6 Lesson 2

Dune

A pile of windblown sand.

Abrasion

The grinding away of rock or other surfaces as particles carried by wind, water, or ice scrape against them.

How does water deposition change Earth's surface?

Water deposition changes Earth's surface by causing sandy beaches to form. This occurs when longshore currents transport the sand along coasts and eventually, sand is deposited where currents are slower and have less energy. Dripping groundwater can develop into stalactites and stalagmites. A stream slows and deposits sediment when it reaches flat land or a large body of water, forming a delta. Slower moving water deposits on the inside curves of meanders.

How does water erosion form a cave?

Water erosion forms a cave when carbon dioxide in the air mixes with rainwater, causing a weak acid to form. Some of this rainwater become groundwater, and as acidic groundwater seeps through rock and soil, it can pass through layers of limestone. The acidic water dissolves and washes away the limestone, forming a cave.

Meander

A broad, C-shaped curve in a stream.

Loess

A crumbly, windblown deposit of silt and clay.

Longshore Current

A current that flows parallel to the shoreline.

Delta

A large deposit of sediment that forms where a stream enters a large body of water.

What are some ways human activities affect water erosion?

Some ways human activities affect water erosion is people build structures such as retaining walls, or groins. They are built to trap sediment and reduce the erosive effects of longshore currents. Sometimes people build dams on rivers, which prevents river sans from reaching beaches. Some people also build levees to decrease flooding on a floodplain.

Describe the stream development stages.

Streams change as they flow from steep slopes to gentle slopes and finally to flat plains. Water in a young stream is usually very rapid and it flows downhill. The rushing water often carves v-shaped valleys. Water in a young stream slows as it reaches gentler slopes, and it's called a mature stream. Slower moving water erodes the sides of the stream channel more than its bottom, and the stream develops curves. When a stream reaches flat land, it moves even slower and is called an old stream. More erosion occurs on the outside bends where the water is flowing faster, and more deposition occurs on the inside bends where the water flows slower.

How does water erosion change Earth's surface?

Water erosion changes Earth's surface in several ways. For example, a young stream carves v-shaped valleys in rock and an old stream erodes its sides, causing meanders to form. A longshore current also changes Earth's surface by moving sand toward the shore at an angle, causing the sand to move along the shore in the direction of the longshore current. Coastal erosion can carve rock when waves smash against it. Erosional features such as sea arches and sea stacks can form when waves erode less resistant rocks along the shore. Groundwater erosion occurs when water turns into acidic water, seeps through limestone, and forms a cave.

How do wind erosion and deposition change Earth's surface?

Wind erosion changes Earth's surface when it causes abrasion, which is the grinding away of rock or other surfaces as particles carried by wind, water, or ice scrape against them. As wind carries sediment along, the sediment cuts and polishes exposed rock. Wind deposition changes Earth's surface by causing dunes and loess to form. A dune is a pile of windblown sand and it forms overtime as wind continues to blow sand and deposit it. A loess is a crumbly, windblown deposit of silt and clay. Wind pick up fine-grained sediment that was deposited by glaciers and and redeposits it as thick layer of dust called loess.