coastal processes.ppt

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 The

Coast: 

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Winter 

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 About coast

Coastal region constantly changesalong their length. 

But general character tends to

similar for thousands of km. Mostly coast classified as

• Erosion

• Deposition  Many people live in coastal regions

• 80% of people in U.S. live within easyaccess of coast

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What is coast

The strip of land between the

coastline and the inland locationwhere there is no longer anyenvironmental influence of the

ocean.

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Coast defination

Strip of land that extends from the

shore inland to seaward limit of terrain that is unaffected by marineprocesses.

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Erosional coasts

coast were actively erodedby wave actionby river erosion

by glacierswhen sea level was lower than it isnow

Dominated by sea cliff and rockyshores

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Fig. 10.4

Erosional Coastline

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Depositional coasts

Develop where sedimentsaccumulate either from alocal source

or being transported to the area inrivers and glaciersor by ocean currents and waves.

Include deltas mangroves swampssalt marshes barrier islands andbeach sand dunes

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Depositional shorelines

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Depositional

shorelines  Primarily deposited

by longshore drift 

Beach

Spit

Bay barrier Tombolo

Barrier island

Delta

Beachcompartment 

Fig. 10.7

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Coast classification

Secondary coastsshaped by marine erosion ordeposition caused by wave action

sediment transport by currentsand marine organisms

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Formation of coast

Tectonic processes

Land slides

Isostatic and eustatic sea levelchanges

Glaciers

River borne sediments Biological processes

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Tectonic processes

Lithospheric plates creat majortopographic features of oceanic floor.

Plate tectonic process is slow but

continuously modifying coasts. Hot spots by volcanic eruption like

Hawaii.

By volcanic eruption in magmaticarcs at convergent plateboundrieslike Indonesia.

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Convergence

Divergence 

S

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Tectonic processes uplifted anddestroyed coasts.

Earthquakes at convergent plateboundaries or at transform faultscause sections of coastal land to

move vertically downward.

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Land Slides

Landslides are smaller but importantprocesses of coastline modification.

Destruction of old and formation of new is

dramatic where volcanoes forms islands. Steepflankes overcome terrestrial

margins.

Steepflankes become unstable due toeruption or sinks isostaticaly after movinghot spots.

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Isostatic Sea level changes

Equilibrium ,compareable tobuoyancy in which rigid lithosphericplates floats on underlying mantal.

It occurs locally or regionaly .

Sealevel change on particular setionof coast due to sink or rise of continent isostaticaly.

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Global warming and changing sea

level About 0.6oC

(1.1oF) warmerover last 130years

Sea level rose10-15 cm (4-10 in) overpast 100 years

If globalwarmingcontinues,higher sea levelFig. 10.15

P

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Eustatic Changes

Equlibrium level of ocean surface.These changes take place inresponse of changes in ocean volume

and world wide . Uniform changes are world wide.

Sea level rising slowly due to

Melting of glaciers Warming and expension of ocean

water

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Glaciers

Scoure out steep sided valleys with flow.

Sediments transport and deposit by icemeltings.

Moraines are sediments deposits at glacierends.

Last 15000 years earth climate warmed

and glaciers retreated , each one left oneor more sedimentry deposits calledMoraines.

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glaciers

The rising sea inundated many steep sidedvalleys cut by glaciers and createddeep,narrow,Fgords.

Fgords are long narrow inlets ,generallywell protected from erosion by oceanwaves and their shores are little alteredfrom original sides of glacial valleys.

Examples south island of New zealand inScandinavia ,and Pacific coast of Canadaand Alaska.

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River Borne Sediments

New coasts found where largeamount of R B S deposited .

Delta of Mississippi river is exampleof R B S.

Only a few rivers carry such largesediment load that their river valleysfilled large quantity of sediments tobe transported.

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Biological Process

Reef building CorelReef means rocky elevation of seafloorwhose upper part is at depth of less thanabout 20 m. Corel maysecrete external Skelton of calciumcarbonate.

It can not grow and build reef unless theyare under water.

Reef grow fastest in shallow water due tolight . And some reef tops emerge abovewater at low tides.

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Types of Reef 

Fringing Reef that is attached to the shore of anisland or continent with no open

water lagoon between reef andshore.

Barrier Reef coral reef that parallel the shore butis separated from land mass by openwater.

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Wave Refraction 

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Lower energy,

sand settles out 

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Fig. 10.12

P

10 02a

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10_02a

S

Summer 

U S t Erosion or deposition

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U.S. coasts Erosion or deposition

dominates

Type of bedrock

Tidal range and waveexposure

Active tectonics

Eustatic changes in sea level

Fig 10 16