Eustatic – global-scale sea level change caused
by a change in the volume of water in the ocean
Isostatic – local-scale sea level change caused by
a change in the level of the land relative to the
level of the sea.
Emergence – the impact of a relative FALL in sea
level (Marine Regression)
Submergence – the impact of a RISE in relative
sea level (Marine Transgression)
A decrease in global temperatures leads to
more precipitation occurring in the form of
Eventually this snow turns to ice and so water is
stored on land rather than being returned to
the ocean store.
Consequently there is a global FALL in sea level.
If global temperatures subsequently rise,
glaciers retreat and ice melts causing a RISE in
global sea level.
During a glacial period, the weight of ice in
ice sheets and glaciers adds weight to the
This causes the crust to sink lower into the
mantle rock beneath.
This results in an apparent rise in the level of
At the end of the glacial period the ice melts
and weight is lost from the crust causing it to
slowly rise. The sea level will then appear to
Some places on the east coast of Scotland
are rising at a rate of 7mm a year.
Rias are submerged river valleys. The lowest part of theRias are submerged river valleys. The lowest part of the
river’s course and the floodplains alongside the river mayriver’s course and the floodplains alongside the river may
be completely drowned, but the higher land remainsbe completely drowned, but the higher land remains
exposed, e.g. Kingsbridge Estuary, Devonexposed, e.g. Kingsbridge Estuary, Devon
In cross section the ria has relatively shallow
water becoming increasingly deep towards the
centre. The exposed valley sides are quite
In long section rias are quite even with a
smooth profile and water of uniform depth.
In plan view they tend to be winding,
reflecting the original route of the river and
Fjords are submerged glacial valleys. They have steep,Fjords are submerged glacial valleys. They have steep,
cliff-like valley sides and the water is uniformly deepcliff-like valley sides and the water is uniformly deep
(often 1000m in depth). These were formed when glaciers(often 1000m in depth). These were formed when glaciers
eroded below sea-level. When the ice melted the valleyseroded below sea-level. When the ice melted the valleys
were flooded, e.g. Milford Sound fjord, New Zealandwere flooded, e.g. Milford Sound fjord, New Zealand
The u-shaped cross-section reflects the
original shape of the glacial valley.
Unlike rias, fjords are not deepest at their
mouths, but have a shallow section at the
seaward end known as the threshold.
Fjords have much straighter routes, due to
the erosive power of the glacier.
Raised beaches, e.g. Little Gruinard, Ullapool are areas ofRaised beaches, e.g. Little Gruinard, Ullapool are areas of
former wave-cut platforms and their beaches which areformer wave-cut platforms and their beaches which are
left at a higher level than the present coastline.left at a higher level than the present coastline.
Abandoned cliffs, caves and stacks can also be foundAbandoned cliffs, caves and stacks can also be found..