Sealevel Changes and Landforms

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Sealevel Changes and Landforms

• Miss B

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How does Sea level Change?

• There are two types of change
• 1- Eustatic - Global rise in sea water levels
  related to the melt-water.
• 2- Isostatic adjustment of land levels related to
  changes in the weight of ice-cover. These
  isostatic adjustments were regional because the
  crust rebounded only in the regions around the
  ice sheets (ie. in North America, Antarctica,
  Greenland and Eurasia).

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Emergent Coasts

• Emergent coastlines form when
• 1- Sealevel is falling
• 2- Land is uplifted
• Coastlines are usually straight

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Emergent Landforms
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Raised Beaches

• These are remnants of former coastlines
• A good example is Portland in Dorset

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Relict Cliffs

• This relict cliff line provides a clear boundary
  between the reclaimed marsh tothe north and
  rolling farmland to the south

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• Good examples of Relict Cliffs are found in
  Scotland. During the last Ice Age, some 100 000
  years ago Scotland was depressed due to the
  weight of the ice (isostatic load). When the ice
  melted there was isostatic uplift causing a
  regression.

• This photo shows three distinct cliffs, picked
  out by pale slopes, each flat area is a beach.

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Coastal Plains

• Sedimentary rocks, deposited mostly in a marine
  environment can be uplifted form a large flat
  Coastal Plain.

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Submergent Coasts

• Submergent Coasts form when
• 1- Sea level Rises
• 2- Land is sinking

• Coast lines are usually Irregular because they
  drown landscapes that have been cut into by
  rivers.

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Submergent Landforms
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Rias

• What is a ria ?
• A deep, sunken river valley drowned by the sea.

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• They form funnel-shaped branching inlets,
  decreasing in depth and width inland.
• This is Solva in Pembrokeshire.

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Fjords

• Narrow, lengthened and steep marine Gulf, which
  results from the invasion by the sea of a
  U-shaped valley dug by a glacier

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Fjards

• Fjards drowned glacial lowlands occur in
  glaciated, low relief areas, such as western
  Scotland.
• They typically have associated islands which are
  highly indented (skerries) and result from the
  emergence of land following the last ice age.

• Bantry Bay Ireland

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Barrier Beaches

• Shingle beaches such as Slapton Sands and Chesil
  Beach were pushed ashore during a transgression.
• As the sea level rose, the horizontal progress of
  the sea across the dry shelf would have swept the
  sediments before it, a process called
  bulldozerisation.

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• THE END

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