Coastal landscapes and change eq3

What is Eustatic change. What causes eustatic fall and rise

It is change in global sea level, usually due to a change in the volume of water in the oceans.

Eustatic fall caused during glacial periods when ice sheets form in land in high latitudes, water evaporated form the sea is locked up on land as ice, leading to global fall in sea level.

Eustatic rise caused at the end of a glacial period, melting ice sheets return water to the sea and sea level rises globally. Global temperature increases and caused the volume of ocean water to increase (thermal expansion) leading to sea level rise.

What is isostatic change and washes isostatic fall and rise

A change in local land level.

Isostatic fall caused by post glacial adjustment (Isostatic rebound adjustment) where the weight of the ice makes the crust sag. When the ice melts the land slowly rebounds upwards, lifting the land surface out of the sea. Also caused by subsidence e.g. the weight of sediment leading to very slow crustal sag.

Isostatic rise caused by post glacial adjustment, accretion (sink regions in sediment cells experiencing net deposition so land is being built up leading to fall in sea level)

Accretion meaning

The accumulation of sand or land mass over time along coastal regions

Transgression meaning

The migration of shoreline out of a basin and onto land during recession

Regression meaning

A return to a former state

What are the two different groups of landforms

Submergant and emergent.

Submergant is coastlines where land is sinking relative to sea level. Caused by sea level rise, land subsidence.

Emergent is coastlines where land is rising relative to sea level. Caused by Isostatic rebound, sea level fall.

how do submergant landforms form and the 6 examples

A rise in sea level floods the coast and creates the landform. E.g. ria, barrier island, Dalmatian coast, fjord, fjard

How do emergent landforms form and the 2 examples

A fall in sea level exposes land previously covered by the sea and crested the landform. E.g. raised beach, fossil cliff

formation of raised beaches (emergent) and an example

Formed when the sea was previously at a higher level and has fallen. The raised shore platform (often with beach deposits creating a terrace and an area of flat land) is backed by the relict cliffs.

E.g. Isle of Arran coastline

Formation of fossil cliffs/ relict (emergent) and an example

a steep slope found at the back of a raised beach exhibiting evidence of formation through marine erosion but now some distance inland. May contain other coastal erosional features such as caves, wave cut platforms.

E.g. Isle of Arran

Formation of a Fjord (submergant) and an example

It’s a drowned glacial valley. Glaciers eroded U shaped valleys down to the coast. After the ice melted, the sea level rose again and flooded into the valley over a shallow threshold creating a very deed water inlet with steep sides. They have features such as hanging valleys and truncated spurs.

E.g. Milford sound in New Zealand

How a fjärd forms (submergant) and an example

It’s a flooded inlet with low rocky banks on either side. Formed by post glacial drowning of glacial lowland rocky terrain. Wider and less steep than fjords.

E.g. the gulf of finland

Formation of Dalmatian coasts (submergant) and an example

Feature several linked parallel flooded valleys with long islands between them. This is a result of submergence when sea levels rose and flooded the valleyy between mountain ridges parallel to the coast

Implications of sea level rise

Agricultural land, roads, communication, power stations lost from flooding. Underground water reservoirs contaminated affecting domestic supplies and irrigation by salt water moving upstream. Wetlands and salt marsh habitats lost

What happens to Tuvalu (a series of low lying atolls (ring shaped coral reef islands or series of inlets)) in relation to sea level rise.

How high above sea level is it, how many live there and how many given visas yearly, how much has Australia raised and for what, how much higher is sea level now

Its at risk firm rising sees as it’s not high above sea level being an atoll 4.6 pm above sea level

Home to 11,200 people. Up to 280 people a year are granted visas to live and work in Australia.

A$ 16.9 million given by Australia to expand the landmass of its main island by 6% to adapt.

Sea level 6 inches higher than 30 years ago.

What happened in Hallsands, Devon 1917

A NE gale with wave of over 12m combined with a high tide destroyed 29 houses and lowered the beach level by 2m. This is because they already dredged the sea for sediment to expand the Devon port dockyard. This made the sea deeper. The waves couldn’t break offshore because the water was too deep. The beach disappeared to fill the hole so there was no beach to protect the coast.