1. Erosional Forces 7.1 Gravity

2. Erosion and Deposition • Erosion – process that wears away surface materials and moves them from one place to another. • Major causes – gravity, glaciers, wind, and water • Deposition – dropping of sediment in a new location. • The final stage of erosion. • Erosion and Deposition by Gravity • Gravity – force of attraction that exists between all objects • Gravity causes loose materials to move down a slope. • Mass Movement – erosion that occurs due to gravitational pull on a down slope.

3. Slump • Slump- mass movement that happens when loose materials or rock layers slip down a slope. • Happens when layers underneath can not support the rock and sediment above. • Creep • Creep – sediments that slowly inch their way down a hill. • Frequent in areas of freezing and thawing • Rockslides • Large blocks of rock break loose form a steep slope ad start tumbling • Occur in mountainous areas or where there are steep cliffs • Most often happen after heavy rains, or during earthquakes

4. Mudflows • Occur in dry areas where there are thick layers of dry sediments • Often after a heavy rain • Erosion-Prone Land • Building on Steep Slopes • Prone to slumps because of weak sediment layers underneath. • Removal of vegetation or increasing slope speeds up erosion. • Making Steep Slopes Safe • Plant vegetation • Build walls or terraces • Can only slow erosion, never eliminate Pg. 189 1-4