Agents of Erosion

Agents of Erosion❖ Erosion - process by which natural forces move weathered

rock and soil from one place to another

❖ Agents of erosion:

Running Water & Waves

Glaciers

Wind

Living Things

❖ GRAVITY is driving force

Running Water❖ Main agent of erosion

❖ Runoff - water that moves over Earth’s surface

❖ Runoff depends on:

Amount of rain

Amount of vegetation

Type of soil

Shape of land

How people use land

Running Water❖ As water moves, it carries sediment with it

❖ Ability of river to erode depends on:

River’s slope

Volume of flow

Shape of stream bed

❖ FEATURES: V-shaped valleys, waterfalls, rounded rocks, meanders, deltas, flood plains, alluvial fans, and oxbow lakes

Running Water❖ Rill Erosion - when running water cuts small channels into

side of a slope

❖ Gully Erosion - when channel becomes deep and wide; rill erosion evolves into gully erosion

❖ Cause major problems in farming and grazing areas (carry away fertile agricultural soil)

❖ Waves contain energy - shape coast by breaking down rock and transporting sand and other sediment

❖ Longshore Drift - waves hit land at an angle and push material along beach

❖ Groins, jetties, and piers - barriers to prevent erosion

❖ FEATURES: beaches, spits, sandbars, and barrier islands

Waves

Glaciers❖ Glaciers - large moving masses of ice that form near

Earth’s poles and in mountain areas

❖ Scrape and gouge out large sections of Earth’s landscape

❖ Carry huge rocks/piles of debris great distances

❖ Grind rocks into flour-sized particles

❖ FEATURES: U-shaped valleys, kettle lakes, rocks with striations, moraines, tills, and drumlins

Wind❖ Weakest form of erosion

❖ Prominent in flat, arid, bare (little vegetation) areas such as beaches and deserts

❖ Wind Breaks - farming method of planting trees/vegetation perpendicular to direction of wind

❖ FEATURES: sand dunes, rock pedestals, smooth angular rocks with pitted surfaces

Living Things❖ As plants and animals carry out their life processes, they

move Earth’s surface materials from one place to another

❖ FEATURES: burrows, gardens, buildings, and roads