Sea Level Changes Flashcards
Sea level changes are…
Eustatic or isostatic
Eustatic sea level change
A global change in sea level resulting from a fall or rise in the level of the sea itself (volume of water in the sea changes/change in the shape of the ocean basins)
Eustatic change causes (2 points)
- Changes in climate
- increase in temp = ice sheets melt, water expands (increased sea level)
- decrease in temp = more snow, more water stored in glaciers so volume of sea is reduced (sea level decreases) - Tectonic movement
- shape of ocean basins are altered and thus volume also
Eustatic change always has g______ effects
GLOBAL
Downward movement of the land causes…
Sea level to rise locally
Uplift of land causes…
Sea level to fall
Isostatic sea level change
Local changes in sea level resulting from the land rising and falling relative to the sea
Even today, ___ years after the last ___ _____ ended the UK is still readjusting to not having its ___ load
10 million
Ice age
Icy
UK Isostatic Change Situation
The north of the UK is rising, e.g Ben Nevis at 2mm per year
The south of the UK is sinking, e.g Brighton at -0.4mm per year
The main causes of isostatic sea level change are… (3 points)
- Uplift/depression of Earth’s crust
- Melting ice sheets = uplift as no more weight on land (rebound)
- Accumulation of sediment = depression - Subsidence of land
- caused by shrinkage of land after abstraction of groundwater - Tectonic processes
Tectonic movement leads to an _______ in surface area of land. This means that the water is more ____________ into a ___________ area and so ocean depths increase.
Increase
Condensed
Smaller
Tectonic Process Explanation
- Global temps cool, ice forms as glaciers and ice sheets
- These ice forms reduce water in oceans (eustatic fall)
- The relative fall in sea level is moderated by the ice that forces land to move down (Isostatic change)
- Climate warms ice melts sea level rise
- Flooding occurs, submergent features form
- Once ice is removed Isostatic rebound can occur - slow
- Prolonged rebound - allows emergent features such as raised beaches which sit above sea level
Isostatic changes + eustatic changes =
FLOODING
Land sinking and sea level rising
Sea level has _____ in the last _________ years
Risen
10,000
Sea level varies on a _____ basis with the tidal cycle.
Onshore winds and ______ atmospheric pressure systems also called the sea surface to _____ temporarily.
Daily
Low
Rise
Draw time line of global sea level
Refer to textbook
Climate change causes changes in
Sea level
Change in average temperature between 1900 and 2016
1.08 C
Causes of climate change and HOW they cause it
Human activities (deforestation and burning fossil fuels)
Increase conc of greenhouse gases, these absorb outgoing long-wave radiation, so less is lost to space
As more energy is trapped the plant warms up
Impacts of climate change
Increase in sea level through melting ice sheets and thermal expansion of water in oceans
Global sea level is currently rising at _mm per year
2
Impacts of climate change on coastal areas…
- More frequent and severe coastal flooding
- Submergence of low-lying islands
- Changes in the coastline, e.g island formation
- Contamination of water sources and farm land (salt)
- More coastal erosion and stronger storms
SEA LEVEL FALL results in
Coastlines of emergence
Landforms of emergence (3)
Raised beaches
Relict/fossil cliffs
Marine terraces
Raised Beaches
Formation?
Example?
Formed by wave action
Fall in sea level/rise in land puts beach beyond the waters reach at the high tide mark
West Coast of Scotland
Marine terraces
Formation?
Example?
Sea level falls
Wave cut platforms exposed
Land uplifted
Platforms preserved as terraces above the ocean
Croatia
Relict/fossil cliffs
Formation?
Example?
The cliffs are no longer exposed by the sea and slowly get covered by vegetation
These raised features are gradually weathered over time
SEA LEVEL RISE results in
Coastlines of submergence
Landforms of submergence
Rise
Fjords
Dalmatian coastlines
Rias
Formation?
Example?
Water enters a valley and partially submerges it
Rias have a gentle long and cross profile
Wide and deep at mouth
Narrower and shallower inland
Milford Haven, South Wales
Fjords
Formation?
Example?
Movement of a glacier that cuts rock formations
Steep ridges formed on each side of glacial valley
Valley fills with water
Western Norway
Dalmatian coastlines
Formation?
Example?
Valley lies parallel to coast
Increase in sea level
Valley flooded
Islands left parallel to the coastline
Named after the Dalmatian coast in Croatia
The sea level changes due to 2 factors
Subsistence of the coastline
Increase in water volume of the ocean
Subsistence
Coastal areas sinking - often this is due to access groundwater extraction. Has the effect of making the sea level higher
Water volume
Changes due to either thermal expansion or addition of extra water from land stores (ice melt)
Processes _____ and _____ landforms over time
Create
Alter
Individual ________ combine to form _________. Coastal landscapes can be dominated by ________ or _________ but both are formed by both
Landforms
Landscapes
Erosion
Deposition
A change in one factor leads to changes in others.
Example?
Change in wind direction could increase deposition and change a landscape dominated by erosional landforms to one dominated by depositional landforms
Changes can occur over a range of _____ scales and ______ scales
Spatial
Temporal
E.g storm - hours
Tectonic uplift - thousands of years
The Maldives: Sea Level Rise
3mm per year
Airport - 1.2m above sea level, only point of access
1.2 million tourists per year
1/3 of GDP tourism
