Weathering All of the processes that break rock into smaller pieces Rocks can be weathered only when they are exposed to the earth’s surface.

There are 2 types of weathering: Physical : The ways in which rock breaks down into smaller pieces without any chemical change in the materials of the rock. *Also known as MECHANICAL Examples of physical weathering include: a. Frost action: water enters cracks in rock & freezes. b. Root action: roots work their way into rocks (plants can do this). c. Thermal expansion: heating and cooling (wind) d. Abrasion: rocks come in contact with other rocks.

Chemical: the ways in which rock breaks down by chemically changing some of the materials in the rock. *takes place best in hot, wet climates. *Agents of chemical weathering include: a. Water b. Oxygen (rusting by oxidation) c. Carbon dioxide (carbon dioxide + water = acid d. Living organisms (lichens: fungi + algae) *plants can be both physical and chemical weathering

Erosion The carrying away of weathered material. Once a rock has been broken down by weathering, rock particles and soil can be moved by several means. These include: gravity, streams, ice/glaciers, wind, or waves.

Types of Erosion Erosion by Gravity: Pulls pieces of rock to the bottom of a slope. *This type of erosion causes: landslides, creep, and slump Erosion by Streams: *Happens one of 2 ways. 1. soil and rock are carried away, and water does not change the rock. 2. when particles are carried away by the water’s current, they wear away the channel through which the stream flows. *This type of erosion forms: valleys, canyons, dunes, deltas, and mountain bowls

Erosion by Glaciers: Like huge plows, they carve and shape large parts of the Earth’s surface. *This type of erosion forms sharp mountain peaks, wide valleys, level plains, and lakes. Erosion by Wind: Moves only small rock particles like sand and dust. *This type of erosion has the greatest effect in dry, desert climates. Erosion by Waves: The constant pounding of waves erodes the rocks along the shoreline. **Careless use of land by humans speeds the rate of erosion

Deposition All of the processes by which eroded materials are dropped. There are 4 types of deposits. 1. stream 2. glacial 3. wind 4. waves

Types of Deposits Stream Deposits *Rock and soil are carried any place where the flow slows down. *These are most commonly found: a. At the base of mountains b. At the edge of stream channels c. Where rivers meet a lake or ocean Glacial Deposits *Moving glaciers pick up a great deal of rock when the glacier stops advancing and begins to melt Wind Deposits *The sand, silt, and dust carried by the wind is deposited when the wind encounters a barrier and slows down.