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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