Sea level change

• Sea levels change in short-term period such as day-to-day or minute to minute due to factors such as high tide and low tide , wind strength and changes in wind direction or changes in atmospheric pressure
• Sea level change also occurs over long-term periods, leading to the formation of various coastal landforms as a result of the following processes:

  • Isostatic Change
  • Eustatic Change
• Isostatic change occurs when the land rises or falls relative to the sea and is a localised change
• Isostatic sea level change is often a result of isostatic subsidence (glaciers weigh down the land beneath, and so the land subsides). When the glaciers melted, this has lead to isostatic recovery and the coastline to rebound and rise again in the areas that were covered by ice
• Eustatic change affects sea level across the whole planet. You can remember this using Eustatic affects Everywhere.
• Eustatic change may be due to thermal expansion/contraction or changes in glacial processes. Thermal expansion is the process of water expanding when it gets warmer, and so the volume of water increases leading to rising sea levels. In the last ice age, sea levels were over 100m lower than they are currently due as the water was stored in large ice caps as the majority of precipitation fell as snow. When the ice caps melted, this lead to rising sea levels.
• Emergent Coastal Landforms where the land has been raised in relation to the coastline, landforms such as arches, stacks and stumps may be preserved. Raised beaches are common before cliffs which are also raised (relic cliffs), with wave-cut notches and similar features proof of historical marine erosion.
• Submergent Coastal Landforms Landforms of submergence occur when the sea level rises or the coastline sinks in relation to the sea. An easy way to imagine the effects of rising sea levels is to picture a mountainous area close to the coast and then imagine sea level rising by around 100m leading to some of the valley’s being flooded
• Rising sea levels leads to the following landforms:

  • Rias
  • Fjords
  • Dalmatian Coasts
• Rias are formed when rising sea levels flood narrow winding inlets and river valleys . They are deeper at the mouth of the inlet, with the water depth decreasing further inland.
• Fjords are formed when rising sea levels flood deep glacial valleys to create natural inlets and harbours . Fjords can be found across the world though in some countries such as New Zealand they may be referred to as sounds. They are deeper in the middle section than they are at the mouth, with the shallower section identifying where the glacier left the valley.
• Dalmatian Coasts: This type of coastline occurs when valleys running parallel to the coast become flooded as a result of sea level change. This leaves a series of narrow, long and rugged islands and the best examples can be seen in Croatia. They may also be referred to as Pacific coasts
• A Fjord is a glaciated carved U-shaped valley that is filled by rising sea water levels.

  It is a long, narrow inlet with steep sides. They have shallow mouths formed by deposition of material from the glacier, They are very deep (up 1000m) further inland

  Best examples are in Norway
• A ria is a landform, often referred to as a drowned river valley. Are almost always estuaries. Form when valleys which were previously at sea level become submerged. They are wide and deep at the mouth and become narrower and shallower further inland.
• Dalmatian Coasts are longitudinal coastlines that undergo submergence. Where valleys lie parallel to the coast, they are flooded by sea level rise leaving islands parallel to the coastline. They form broad open sounds with ridges of land / islands.