Erosion

Weathering breaks down the rock. Erosion is the natural process which move weathered rock and soil from one place to another. Deposition is where agents of erosion lay down sediment

Weathering, erosion and deposition act together in a cycle that wears down and builds up the Earth’s surface. Equilibrium- a state of BALANCE

Agents of Erosion: The motions of… Mass Movement (landslides) Caused by gravity and rain Water Ocean Waves Rivers and streams Wind Moving Ice Glaciers

Water Most important agent of erosion water carries more sediment then any other agent of erosion.

Methods of water transport Solution Suspension Flotation Bed load The method is determined by the size of the particle and speed of the moving water. Faster water = larger particles

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Solution Sediments are dissolved in water Smallest particles, cannot be seen

Suspension Objects that float Silt clay and colloids are so small they deposit in water very slowly and stay suspended until water stops moving.

Bed Load Cobbles and boulders that roll or bounce along the bottom of a stream Larger particles will deposit faster.

Discharge… The amount of water flowing past an area in a given moment is called a streams discharge. More runoff from land = more discharge. More discharge = more water = faster velocity = larger particles in suspension.

Where do Streams and Rivers get there water from? Watershed or Drainage Basin A drainage basin is the land area from which a river collects its water. Small streams that feed the river are called tributaries.

Hudson Valley Drainage Basin.. Local Tributaries… Wappingers Creek Fishkill Creek Wallkill River Esopus Creek Rondout Creek Sprout Creek

Drainage Patterns… There are 4 drainage patterns: Radial Annular Dendritic Rectangular The type of pattern depends on the bedrock structure below.

Radial

Annular

Dendritic

Rectangular

Features of a stream or river… Meander Oxbow Lakes Waterfalls V-shaped Valleys Head Mouth Rapids

Mature (old) Rivers Mature rivers will have gentle slopes, slow moving water, flood plains, meanders, and oxbow lakes, deltas. These features are located near the mouth (end) of the river.

Youthful (new) Rivers Youthful Rivers will have steep slopes, fast moving water, rapids, waterfalls, V-shaped valleys. These features will be found near the head (beginning) of the river.

Stream Erosion and Depostion within a Meander… As a river turns within a meander, the outside of the turn has the faster water velocity. The inside of turn has slower water velocity. This creates erosion on outside of turn and deposition on inside of turn. If stream is straight (no meander), the velocity is greatest in the middle and slowest along the sides.

Wind Strong winds transport sediment Happens in deserts and at beaches Softer rocks erode faster

Glaciers A large mass of ice that flows over land or in valleys