Coastal Geography, Sea Level Change Flashcards
What are the three main causes of sea level rise?
Short term causes (tides, winds, floods), changes in water temperature (thermal expansion), and elevation in Equator due to increased temperature
What are the three main types of long term change in sea level?
Changes in ocean basin volume, ocean water volume, and ocean distribution
Ocean basin volume
Changes occur due to plate tectonics and isostatic adjustment
Ocean water volume
Location of seafloor. Changes occur due to climate change and thermal expansion
Ocean distribution
Changes occur due to effects of gravity/Earth’s rotation
What is the most significant component of the hydrological cycle?
There is a finite anmount of water in the system, 97% of which is stored in the ocean
Eustasy
The rise and fall of sea level due to changes in ocean volume
Glacio-eustasy
The global change in absolute sea level caused by the melting or expansion of ice sheets
Isostasy
The rise or fall in land due to changes in elevation of the Earth’s crust. This changes relative sea level
Glacio-isostasy
The regional/local rise or fall of land caused by the melting or expansion of ice sheets
What are the four primary long term controls on sea level?
Eustasy, glacio-eustasy, isotasy, and glacio-isostasy
What were ice sheets like 20,000 years ago during the Last Glacial Maximum?
There were two major ice sheets (2Km thick) in the Northern Hemipshere which covered parts of North America and Russia
What were the names of these two ice sheets?
North America: Laurentide ice sheet
Russia: Fennoscandian ice sheet
What are the three relevant epochs of the geological timescale and what period do they belong to?
The Pleistocene, Holocene, and Anthropocene which all belong to the Quaternary period
What is the general pattern of glacio-eustatic sea level rise?
Absolute sea level has always fluctauted but it was 120,000 years ago when present day sea levels can be observed
What are two types of evidence for changing sea levels?
Past coastal stacks (both above and below sea) and unconvential forest locations
Sea level stillstand in New Zealand and Australia
In New Zealand and Australia, sea level reached its current position 6000 years ago, rising 1.3m every century since the last glacial period. This has given New Zealand’s coasts 6000 years to change and develop
How is the relationship between the Earth’s solid crust and fluid mantle similar to that of an iceberg in water?
Like an iceberg in the ocean, the Earth’s crust is displacing the mantle according to its bulk and density. Like an iceberg, removing weight from the surface will cause the submerged part to rise in order to maintain a floating balance. This is also similar to the 2Km thick ice sheets that were present in the Northern Hemipshere
Why does sea level history vary between coasts?
Sea level history is not globally uniform due to regional differences in the presence of ice sheets. The Northern Hemipshere had two ice sheets 2Km thick whilst the Southern Hemisphere was not compltely glaciated
Isostatic rebound
The slow rising of landmass after ice melts.
How does isostatic background interact with different parts of a landmass?
Rebound is greatest in the centre of the landmass and decreases towards the coastline. This discrepancy in rebound essentially causes the coast to sink, subsequently causing sea level to rise.
What are the two ways that the coast can respond to changes in sea level?
Transgression and regression
Transgression
As sea level rises, the coastline retreats landward, taking sediment with it. Remnants of coastal features are left behind as relicts
Regression
As sea level falls, the coastline is allowed to advance. This can also occur during periods of stable sea leve due to an abundance of sediment washing up onto the shore
Is sea level rising?
Yes, and it has been doing so for the past century. However, there is much less certainty about the future
