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Sunday, 30 September 2012
Kingsbridge Estuary Ria and Sognefjorden Fiord Case Studies
Kingsbridge Estuary Ria, Devon, UK
During the ice age sea levels around the coast of
southwest England were lower than they are now. This
meant rivers such as the one at Kingsbridge Estuary
lowered their level greatly to be at sea level height.
After the ice age when the ice melted and the sea
levels started to rise the area that had been carved
away by the river re-flooded. This gives the Kingsbridge
Estuary its curving shape as it follows the path of the
river. The area is now a sheltered, winding inlet of water
known as a Ria. The estuary is a natural area where the
water is deepest closest to the sea, typical of a Ria.
There is 800 hectares of tidal creeks and mudflats.
Sogne Fjord was formed as glaciers during the last ice age eroded valleys to form deep valleys known as
glacial troughs. When the ice melted these glacial troughs were flooded because of eustatic sea level
change to form long deep narrow inlets with precipitous sides. The valley is U-shaped when looked at as a
cross section. Unlike rias, fiords have a shallower end towards the sea; the inland areas are much deeper.
The shallow end has a rock bar known as a threshold. The Sogne Fjord extends 195km inland and has a
maximum depth of 1308m.