Surface WaterSurface WaterStream landscapes, Stream landscapes,

erosion and depositionerosion and deposition

The Water Cycle Water constantly moves among the

oceans, the atmosphere and on land. This unending circulation of Earth’s water supply is the water cycle.

Evaporation- liquid water to water vapor Precipitation- water vapor to liquid water Infiltration- water absorbed by land (soil,

cracks in rocks) Runoff- water flowing over land

ErosioErosionn Erosion is the Erosion is the

transport transport of of weathered weathered materialmaterial

Caused by Caused by water, wind or water, wind or glaciers.glaciers.

GravityGravity The root cause of all erosionThe root cause of all erosion Materials falling downhill are Materials falling downhill are

called called Mass MovementsMass Movements ExamplesExamples

– LandslidesLandslides– AvalanchesAvalanches– mud flowmud flow– rock fallrock fall

RUNNING RUNNING WATERWATER The most common agent of The most common agent of

erosion on Earth’s surfaceerosion on Earth’s surface Streams or water flowing Streams or water flowing

over the ground pick up over the ground pick up and move material.and move material.

These particles weather These particles weather rocks from rocks from abrasionabrasion

Stream FormationStream Formation Run-off is the Run-off is the

flow of water flow of water over the groundover the ground

Run-off results Run-off results in the formation in the formation of streamsof streams

Streams that Streams that flow into other flow into other streams are streams are called called tributariestributaries

Stream velocityStream velocity Velocity is fastest at the top centerVelocity is fastest at the top center Slowest near the stream bedSlowest near the stream bed Velocity is fastest at the outside of a Velocity is fastest at the outside of a

turnturn Results in rapid erosion and carves Results in rapid erosion and carves

out the deepest part of streamout the deepest part of stream

MeandersMeanders As a stream flows As a stream flows

across the flood across the flood plain, it meanders, plain, it meanders, or curves back and or curves back and forthforth

This is caused by This is caused by erosion over time. erosion over time.

Point bar- deposition occurs on the inside of Point bar- deposition occurs on the inside of the curve where flow slows downthe curve where flow slows down

Cut bank- erosion occurs on the outside of Cut bank- erosion occurs on the outside of the curve where flow is fastestthe curve where flow is fastest

Oxbow lakesOxbow lakes When a meander gets extreme it will When a meander gets extreme it will

erode back on itself and form an oxbow erode back on itself and form an oxbow lakelake

Carrying CapacityCarrying Capacity How much material a stream can carry How much material a stream can carry

relates to the velocity (speed) of water.relates to the velocity (speed) of water.

Particle sizeParticle size Higher velocity = larger sediment Higher velocity = larger sediment

can be carried down streamcan be carried down stream As the stream slows, it deposits larger As the stream slows, it deposits larger

particles.particles.

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Stream VelocityStream Velocity…(see page 6 of …(see page 6 of ESRT)ESRT)

As stream As stream velocity velocity increases, the increases, the volume and sizevolume and size of sediments of sediments being carried being carried increases.increases.Velocity of stream

Volume and particle size

Conversely, as stream velocity Conversely, as stream velocity decreases, the settling rate decreases, the settling rate

increases.increases.

Coarse gravel Finer sand

Finer silt Finest clay

Incoming stream with sediments

STOP!STOP!

River River DepositionDeposition DepositionDeposition is the laying down of is the laying down of

weathered and eroded sediments weathered and eroded sediments (bits and pieces of larger rock (bits and pieces of larger rock masses).masses).

Occurs when velocity of the Occurs when velocity of the erosional agent (water, wind, erosional agent (water, wind, glaciers) decreasesglaciers) decreases

Most deposition occurs in bodies Most deposition occurs in bodies of water.of water.

River depositsRiver depositsDeltas -Deltas -

triangular fan triangular fan shaped shaped deposits that deposits that develop as a develop as a stream or river stream or river flows into a flows into a larger body of larger body of water water

Alluvial fans Alluvial fans –– same kind of same kind of deposits but on deposits but on landland

GLACIAL GLACIAL EROSIONEROSION

As a large mass of ice (at least 100 ft As a large mass of ice (at least 100 ft thick) moves downhill, from gravity, it thick) moves downhill, from gravity, it picks up rock material.picks up rock material.

The material grinds against and The material grinds against and scratches the underlying rock.scratches the underlying rock.

This is called abrasion.This is called abrasion. There are two types of glaciers, valley There are two types of glaciers, valley

glaciers and ice sheetsglaciers and ice sheets

This is a This is a valley glaciervalley glacier, which flows , which flows

like a stream, down hill.like a stream, down hill.

Streams cut V-Streams cut V-shaped valleys due shaped valleys due to downward to downward erosionerosion

Glaciers cut U-Glaciers cut U-shaped valleys shaped valleys due to sideways due to sideways erosionerosion

V

U

http://www.youtube.com/watch?v=FIn0UoeDyVg

YOSEMITE VALLEY, California

Deposition by GlaciersDeposition by Glaciers

As a glacier retreats (ice melts), As a glacier retreats (ice melts), it drops all the material in and it drops all the material in and on it.on it.

Note: the glacier Note: the glacier nevernever moves moves backwards, the front just backwards, the front just melts melts back.back.

A variety of deposits are left A variety of deposits are left behind, some are sorted and behind, some are sorted and some are unsorted.some are unsorted.

GLACIER

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