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Sealevel Changes and Landforms Miss B 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). Emergent Coasts Emergent coastlines form when: 1- Sealevel is falling 2- Land is uplifted Coastlines are usually straight Emergent Landforms Raised Beaches These are remnants of former coastlines A good example is Portland in Dorset Relict Cliffs This relict cliff line provides a clear boundary between the reclaimed marsh to the north and rolling farmland to the south 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. Coastal Plains Sedimentary rocks, deposited mostly in a marine environment can be uplifted form a large flat Coastal Plain. 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. Submergent Landforms Rias What is a ria ? A deep, sunken river valley drowned by the sea. They form funnel- shaped branching inlets, decreasing in depth and width inland. This is Solva in Pembrokeshire. Fjords Narrow, lengthened and steep marine Gulf, which results from the invasion by the sea of a Ushaped valley dug by a glacier Fjards Fjards – drowned glacial lowlands; occur in glaciated, low relief Bantry Bay areas, such as western Ireland Scotland. They typically have associated islands which are highly indented (skerries) and result from the emergence of land following the last ice age. 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. THE END
