IGCSEIGCSEGEOGRAPHYGEOGRAPHYRIVERSRIVERS

PROCESSESPROCESSESANDANDFEATURESFEATURESPRESENTATION 4PRESENTATION 4

THE LIFE OF A RIVERTHE LIFE OF A RIVER

JOURNEY FROM JOURNEY FROM SOURCE TO SOURCE TO MOUTH MOUTH

AN EXPLANATION AN EXPLANATION OF PROCESSESOF PROCESSES AND FEATURES

What happens when water reaches the ground?What happens when water reaches the ground?

CONDENSATIONCONDENSATION

EVAPORATIONEVAPORATION

PRECIPITATIONPRECIPITATION

SEA

LAND

A SIMPLIFIED WATER CYCLEA SIMPLIFIED WATER CYCLE

Key WordsKey Words

EVAPORATIONEVAPORATION

CONDENSATIONCONDENSATION

PRECIPITATIONPRECIPITATION

RUN-OFFRUN-OFF

PERCOLATIONPERCOLATION

GROUND WATERGROUND WATER

WATER STORESWATER STORES

When water vapour changes to liquid (cooling)When water vapour changes to liquid (cooling)

Water in any form that falls to earth e.g. rainWater in any form that falls to earth e.g. rain

When the ground water moves through the landWhen the ground water moves through the land

When water vapour changes to liquid (warming)When water vapour changes to liquid (warming)

The water that is stored within the groundThe water that is stored within the ground

Water that is stored e.g. ground,clouds,air etc.Water that is stored e.g. ground,clouds,air etc.

Water that moves directly along the ground Water that moves directly along the ground without penetrating.without penetrating.

Put the correct definition to the given word~one has been done for youPut the correct definition to the given word~one has been done for you

Detailed Water CycleDetailed Water Cycle

Completed Water CycleCompleted Water Cycle

River BasinsRiver Basins

• Where a river begins is called the source.source.• A small river meeting a larger river is called a tributarytributary.

• Where the two rivers join is called the confluenceconfluence• Where the river flows into the sea is called the mouthmouth.• The area drained by a river is called the drainage basin.drainage basin.

• The ‘line’ that separates two drainage basins is called the watershed.watershed.

Key WordsKey Words

THE LONG PROFILE OF A RIVERTHE LONG PROFILE OF A RIVERUpper CourseUpper Course Middle CourseMiddle Course Lower courseLower course

SOURCESOURCE

MOUTHMOUTH

Key WordsKey WordsHydraulic PowerHydraulic Power

CorrasionCorrasion

CorrosionCorrosion

AttritionAttrition

Water/debris is Water/debris is forced into cracksforced into cracks

Rocks /stones Rocks /stones erode bed and sides erode bed and sides of river bank.of river bank.

Rocks get Rocks get smaller by smaller by chemical actionchemical action

Rocks get smaller when knocked togetherRocks get smaller when knocked together

Rocks such as chalk Rocks such as chalk and Limestoneand Limestone

The Upper Course of a RiverThe Upper Course of a River

• Hydraulic powerHydraulic power

This is the force of the water on the bed and banks of the river, powerful when in flood, the force of the water removes material from the bed and banks of the river.• CorrasionCorrasion

When the river is particularly full, pebbles and boulders are carried along by the water. These rub against the bed and banks of the river and wear them away. The process is called abrasion.

Processes of erosionProcesses of erosion

Processes of ErosionProcesses of Erosion

CorrosionCorrosionRiver water sometimes causes some rock to slowly dissolve. (e.g. limestone dissolves in slightly acid water and is carried away in solution (as a liquid) as calcium hydrogen carbonate).

AttritionAttrition

The pebbles and small rocks being carried by the river - the load - collide and rub against each other, breaking up into smaller and smaller pieces. The rough edges become smooth, forming smaller rounded material. Eventually the particles are reduced to sand and silt-sized particles

Features of the upper course of a riverFeatures of the upper course of a riverThe main features of a Waterfall are:

•A steep drop in the river ~ called a high a high head of waterhead of water

•A plunge poolplunge pool at the base

•Hard, resistant rock at the top~ the cap rockthe cap rock

•Softer rock below that are undercut.undercut.

Waterfalls and gorges are formed over a Waterfalls and gorges are formed over a long period of time they are characterised long period of time they are characterised by the following: -by the following: -

•Bands of hard and soft rock being erodederoded at different rates. (softer rock the quickest)

•The river moves back as the erosion takes place, this is known as recession.recession.

•A gorge and waterfall have steep sidessteep sides

Hard cap rockHard cap rock

(resistant)(resistant)Softer rock is Softer rock is undercut by undercut by

backwash from backwash from falling waterfalling water

Softer less resistant rock is Softer less resistant rock is easily erodedeasily eroded by fast flowing by fast flowing water.water.

Deep plunge Deep plunge pool at base of pool at base of waterfallwaterfall

Undercutting has Undercutting has taken place where taken place where softer rock is foundsofter rock is found

Waterfall over Waterfall over 150 metres high150 metres high

Deep plunge pool at Deep plunge pool at base of waterfallbase of waterfall

The middle course of a riverThe middle course of a riverKey wordsKey words

TractionTraction

-large boulders -large boulders roll along the roll along the

river bedriver bed

SaltationSaltation

-smaller pebbles are bounced along the river bed, picked up -smaller pebbles are bounced along the river bed, picked up and then dropped as the flow of the river changesand then dropped as the flow of the river changes

Key words continuedKey words continued

SuspensionSuspension

-the finer sand and silt-sized particles are carried along in the -the finer sand and silt-sized particles are carried along in the flow, giving the river a brown appearance.flow, giving the river a brown appearance.

SolutionSolution

-minerals, such as limestone and chalk, are dissolved in the -minerals, such as limestone and chalk, are dissolved in the water and carried along in the flow, it often cannot be seen.water and carried along in the flow, it often cannot be seen.

The middle course of a riverThe middle course of a river

•MeandersMeanders

Erosion on Erosion on outside bendoutside bend

Deposition Deposition on inside on inside

bendbend

Feature of the middle courseFeature of the middle course

A Meander (cross-section)A Meander (cross-section)

Label the diagram with the following words and statements:-Label the diagram with the following words and statements:-

Outside bend, inside bend, erosion, deposition, river cliff, Outside bend, inside bend, erosion, deposition, river cliff, deepest water and fastest current.deepest water and fastest current.

BBAA

BBAA

Feature of the middle courseFeature of the middle course

A Meander (cross-section)A Meander (cross-section)

Outside bend, inside bend, erosion, deposition, river cliff, Outside bend, inside bend, erosion, deposition, river cliff, deepest water and fastest current.deepest water and fastest current.

BBAA

BBAA

The lower course of a riverThe lower course of a river

•Ox-bow lakes Ox-bow lakes

•Flood plainsFlood plains

Oxbow or ‘cut-off ’ lake

New course of the river

Steep undercut bankRiver straightens at this point and cuts off the ox-bow

Part of the flood plain