EQ3 Coasts Flashcards
What is eustatic change (give Eg)
When sea level itself rises or falls
Eg- ice formation and melting or thermal Changes
What is isostatic change? Give eg
When the land rises or falls relative to the sea
Eg- post glacial adjustment, tectonics, subsidence
How are fjords formed and where
When deep glacial troughs are flooded
Long and steep sided with u shaped cross section
Norway, chile and New Zealand
What are rias and how and where are they formed
Formed when valleys in a dissected upland area is flooded
Common in south west England
Eg kingsbridge estuary
What are raised beaches and where are they formed
Remains of eroded cliff lines can be found behind a raised beach
Cliff has wave cut notches as evidence of previous marine erosion
Found in west coast of Scotland
Describe eustatic change over a glacial period
Glacials lead to formation of ice sheets
Water evaporates from oceans, falls as snow and compresses as ice - transferring water from water store to ice sheets on land
Sea bed exposed as land
Marine regression
Describe eustatic change over an interglacial period
Ice melts
Water transferred from land store back to oceans, increasing the volume of water in oceans and increasing global sea levels
Rising water temperatures leads to thermal expansion of water - volume increased further
Marine transgression
Rising sea levels flood low land areas
How long do glacial and interglacial periods last
Glacial - 90,000 years
Interglacial - 10,000 years
Why do inter glacial and glacial period occur
Climate change occurs cyclically in milankovitch cycles
Due to changes in earths orbit around the sun
How can a rise in local land level occur?
Post glacial rebound
Accretion
What is accretion
Sink regions in sediment cell experience net deposition
Land built up
So sea level falls
How can a fall in local land level occur
Post glacial adjustment (weight of ice pushing down)
Subsidence of land
How can subsidence lead to fall in local land level
Deposition of sediment in large river deltas
Weight of sediment overcomes threshold and leads to slow crustal sag
OR
Fall in water table from increased evaporation or extraction
So overlying sediment sinks
OR
Heavy buildings push down and result in subsidence
How does weight of ice result in fall and rise in land level
Solid lithosphere forced into plastic asthenosphere
Rigid nature of crust results in see saw effect
Some areas forced up, some areas uplifted in see saw effect
Melting results in opposite occurring
How can sea levels change during to tectonic activity
Uplift or subduction of land by plate boundaries
Creates emergent landforms
Subduction results in submerging land forms
Examples of emergent land forms
Raised beaches - when land uses relative to sea level
Relic Cliffs - steep slope at back of raised beach exhibiting evidence of being formed by marine erosion
Examples of submerging coastal land forms
Dalmatian coasts- flooded valleys parallel to coasts, produces narrow islands parallel to coast
Fjords- drowned glacial valleys
Rias- drowned river valley
What features can create rapid erosion and recession?
Destructive waves with long fetch
Strong longshore drift
Soft geology
Weak Lithology (seaward dips)
what are the risks of living in a delta zone?
storm surge
sea level rise
delta subsidence
what human activities can increase risk of flooding in delta zones?
mangrove removal
straightening and dredging
groundwater extraction
how many people are predicted to have been forced to abandon coastal zones by 2100 (IPCC)
hundreds of millions
how have IPCC predicted sea level will change by 2100
rise by 28-98cm
55cm most likely rise
how have IPCC predicted delta flooding will change by 2100
area of world’s major deltas at risk of flooding will increase by 50%
how have IPCC predicted wind and waves will change by 2100
some evidence of increased winds speeds and larger waves
