Changes on the EarthChanges on the Earth

Weathering and erosionWeathering and erosion

Weathering is Weathering is

• The breakdown of rock at or near the earth’s surface into smaller and smaller pieces

• 2 types– Mechanical– Chemical

Mechanical weatheringMechanical weathering

• Is when rock is actually broken or weakened physically– Produces stones, pebbles, sand, silt, dust– Primary process of soil building

• Caused by water and seeds

Frost wedgingFrost wedging

• When water freezes in the cracks of a rock, it expands and widens the crack eventually causing the rock to split

Seed wedgingSeed wedging

• When a seed takes root in the crack of a rock it also widens the crack

• You’ve probably seen a driveway broken by a tree root

Chemical weatheringChemical weathering

• Alters a rock’s chemical makeup by changing the minerals that form the rock or combining them with new chemical elements

• Acid rain is a form of chemical weathering

ErosionErosion

• Is the movement of weathered material such as gravel, soil, and sand

• 3 main causes– Water– Wind– glaciers

WaterWater

• Is the main cause of erosion

• Forms canyons and valleys

• Rocks and soil carried away are deposited somewhere else creating a new landform

WindWind

• 2nd leading cause; especially where there is little water and few plants to hold soil in place

• sandstorms

GlaciersGlaciers

• Huge slow moving sheets of ice, slide forward because of their weight