A-Level Geography - Physical - Sea Level Change

  • Created by: Noah_S
  • Created on: 29-10-21 15:43
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  • Sea Level Change
    • Causes
      • Isostatic
        • Local land can move vertically in relation to the sea, raising/lowing relative sea levels
        • Land may be pushed down by additional weight from ice or sediment, and when removed isostatic rebound occurs
        • Glacio-isostatic subsidence is where the crust is depressed by ice sheets, like in Scotland
        • Sediment-isostatic subsidence is when sediments accumulate in a large delta, like the Mississippi, depressing the crust
      • Eustatic
        • Fluctuations in the Earth's atmospheric temperature can change the volume of water in the oceans
        • Glaciers & ice sheets melt and retreat, increasing the volume of the oceans
        • Seawater also expands thermally, rising 0.8m for every 1*C rise in temperature
      • Tectonic
        • Techno-Eustatic is if the shape of the ocean basins is altered, their holding capacity will change
          • If capacity is reduced, sea level rise will occur
        • Orogenic movement (mountain building) episodes causes the uplift of the land, resulting in a lowing of relative sea level
          • Occurs at converging plate margins
        • Creation of volcanic ocean islands displaces water and increases sea levels
    • Emergent Landforms
      • Raised Beaches
        • Formed when the fall in sea level leaves beaches above the high tide mark
        • Over time, beach sediment becomes vegetated and develops into soil
      • Relict Cliffs
        • Cliffs above raised beaches are no longer eroded, so they get covered by vegetation
        • Not uncommon to see wave-cut notches, caves, arches and stacks within relict cliffs
          • Degrades over time
      • Information
        • Formed when the relative sea level drops, raising existing coastal landforms upwards
        • Examples can be found in Scotland, as it is being raised due to isostatic rebound
    • Submergent Landforms
      • Rias
        • Formed where river valleys are partially submerged
        • Have a gentle long and cross-profile, deepest at their mouth and becomes narrower and shallower inland
        • Example is Milford Haven in South Wales
      • Fjords
        • Formed from submerged glacial valleys
        • Are straight and narrow, with steep sides. They have a shallow mouth, called the threshold, formed by deposition of glacial sediment
        • Can be very deep, like in Sognefjorden in Norway, which is over 1000m deep in places
      • Dalmatian Coastlines
        • Formed when parallel valleys to the coastline are flooded
        • Have islands parallel to the coastline
        • An example is the Dalmatian Coast in Croatia, which the landform is named after


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