Chapter 3

Section 2

Water Erosion

Water Cycle•Watch the 2 water cycle

animations while reviewing your water cycle diagram.

•When something from your diagram is discussed or shown put a

•If you are missing something, make a note of it on your diagram.

Water Cycle

Water Cycle

SURFACE WATER

RIVERS

(RUNOFF)

Raindrop Erosion

http://www.public.asu.edu/~mschmeec/rainsplash.html

Raindrop Erosion

The force of a falling raindrop can loosen

and pick up soil particles. This starts

the process of erosion.

RIVER EROSION

Why is runoff so important to erosion?

As water moves over land it carries particles with it.

This moving water is runoff and is the major agent of erosion.

5 Factors for the Amount of Runoff:1. Amount of Rain 2. Vegetation

3. Type of Soil

4. Shape of Land

5. How people use the land

Runoff leads to

STREAM

RIVER

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General Statement About Erosion:

More Runoff = More Erosion

Rills are small grooves that runoff creates and travels in the soil.Rills connect together and make larger channels called gullies.Gullies connect together forming larger channels called streams.Streams connect together as larger streams or rivers.(Tributary-any stream/river that flows into a larger one)

RillGullyStreamRiver

How are rills, gullies, streams, tributaries and rivers connected?

What is a drainage basin or watershed?

Parts of a River System::

Drainage basin (watershed)-A land area from which a major river and its tributaries collect its water

(Largest in US-Mississippi River Drainage Basin)

Divide-An area of the land around a drainage basin where the land is high and causes the water to run into that drainage basin.

VALLEYVALLEY

When a river cuts into a steep slope of a mountain or a flat plateau a V-shape will be cut in the land

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Where a river meets an area of rock that is very hard and erodes slowly. The rock below is softer and erodes quickly.

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The river water flows over softer rock downstream.The softer rock wears away faster than the harder rock.Eventually a waterfall develops where the softer rock was removed.

An area downriver where the land is gently sloping.The river will erode a wide, flat area of land instead of a deep valley.When the river floods this land will fill with the excess water.

Flood Plain

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The moving water of a river will erode softer rock before eroding harder rock.This will cause the river to work its way around harder rock and create loop-like bends in the river.Overtime the bends become more and more curved.

Harder rock stays

Softer rock eroded away

A Meandering River

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A meander that has been cut off from the main river during a time of flooding.

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As the floodwaters drop, sediment builds up in front of the openings of the meander and dam up the water inside

forming an oxbow lake.

When the river floods, the high water finds a straighter

route downstream.

River flows through

meander.

Deposition builds up inside meander curve.

RIVER DEPOSITION

Water slows when hits gentle slopeALLUVIAL FAN

Where a stream flows out of a steep, narrow mountain valley, the water slows down, drops sediment in the shape of a wide sloping fan.

Steep mountain

valley

Sediment formsfan-shaped deposit

Water slows when hits gentle slopeALLUVIAL FAN

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When a river meets the ocean or large lake, the water slows down.

The river drops its sediment and can build up new land.

Mississippi River

Green-land built up from deposition

River flooding adds soil to flood plain.

When waters rise, depositiondeposition occurs in the flood plain.

This soil is very fertile.

PAUSE HERE FOR

NIAGARA FALLS VIDEO

GROUNDWATER

(Infiltration)

http://pireamazonia.info/kartchner/flash/

Infiltration- Increasing the amount of groundwater through precipitation or surface water that absorbs (or seeps) into the ground

KARST TOPOGRAPHY

In regions where a layer of limestone is near the surface, groundwater erosion changes the shape of the land.

Water easily sinks down into the limestone.Deep valleys, sinkholes and caverns are common.

KARST TOPOGRAPHY

Before Rain After Rain

Groundwater-underground water causes erosion and deposition.

Water combines with carbon dioxide to make carbonic acid, flows into limestone, dissolves the limestone, and carries the particles away

Caves/Caverns-As limestone is dissolved over time large underground holes form

STALACTITE

STALAGMITE

StalaCtite-As limestone particles in the groundwater is deposited on the Ceiling of a cave an icicle of limestone forms

StalaGmite-As groundwater drips on the Ground of a cave an upside down icicle of limestone forms

SINKHOLE

The roof of a cave collapses resulting in a depression.

The cave roof erodes the limestone too thin.

Guatemala Sinkhole

Feb 24, 2007

END HERE FOR WATER’S

JOURNEY VIDEO