Coastal Environment 3 Flashcards
Physical Factors that affect changes in global temperature and the volume of water in the oceans
Eccentricity- cyclical changes in the shape of earth’s orbit, affecting amount of solar energy reaching planet
Obliquity- changing earth’s tilt influencing geographical distribution of solar energy
Wobble of the Earth’s axis- alters timing between perihelion and aphelion (earth closest to the sun and furthest to the sun), timing of seasons, 26000 years for one wobble to be completed
These are called the Milankovic Cycle, where it alters between glacial and interglacial periods, causes long term climate change
Define Eustatic change
Global change in the volume of water resulting from rise and fall of sea level
Define Isostatic change
Local change in sea level resulting from the land rising or falling relative to the sea
Explain from the last ice age, how sea level changes
During the last ice age (20,000 years ago), sea level drops as ice forms on land- Eustatic change
The weight of the ice pushes down on the land- isostatic change
As ice melts after the ice age, sea level rises- Eustatic change
As there is no ice holding down the land, the land begins to rise again,- isostatic rebound (it is still rising-e.g NW Scotland is rising at about 4mm per year)
-but as the NW Scotland rises, SE of England suffers from compensation depression due to the tilting of the land
Polar ice cap melts, causing sea level rise- Eustatic change
What causes short term climate change (anthropogenic)
Industrial Revolution- increase population, increase dependent on energy, increase burning fossil fuels
Methane and CO2
Agriculture- processing, packaging, food production- increase CO2
Producing 1 kg of meat produces 60kg of greenhouse gases
Deforestation- trees absorb CO2, but deforestation means that less CO2 can be stored and more is in the atmosphere
What causes emergent landforms
Fall in sea level or isostatic uplift
Three types of emergent landforms
Marine Terraces
Abandoned Cliff
Raised Beaches
What are marine terraces
Area where the cliff had been eroded and exposed due to sea level fall
What are abandoned cliffs
Shaped by marine erosion before and is separated by the wave cut platforms from the ocean
What are raised beaches
Used to be marine terraces
As materials from abandoned cliff deposit onto marine platform, it forms raised beaches
What Geomorphic processes could influence emergent landforms, modification considering past and future changes in climate and sea level
Marine processes used to influence them, not anymore after their emergence
Now, mostly sub-aerial processes (mass movement and weathering)
In post glacial periods, increasing temperature could increase the influence of biological and chemical weathering (Van Hoff’s Law)
If temperature gets high enough to lead to sea level rise, then emergent landforms gets closer to the coast, and marine processes may influence
What causes submergent landforms
Rise in sea level or land falls relative to sea level
What are the four types of submergent landforms
Fjords
Rias
Shingle beaches
Estuaries
How are fjords formed
Formed by glaciers eroding the valleys, forming deep glacial troughs
When sea level rise, it floods the valley creating fjords
Example of fjord
Milford Sound in New Zeland
What are rias
They are the drowned river valleys in the upland areas
Example of ria
Kingsbridge Estuary
Last ice age- vertical erosion
After ice age- lower parts of the river drowned
What are Estuaries
Drowned shallow, lowland river valleys
How are shingles beaches formed
The river sediments that previously deposited on the continental shelf when sea level fell are brought onshore by the rising sea level to the present-day coasts
Example of shingle beach
Chesil beach- contains 100 million tonnes of shingle
Jurassic Coast, Dorset
Which two are the greatest submergent landforms
fjords and rias
What Geomorphic processes could influence submergent landforms, modification considering past and future changes in climate and sea level
Rias and fjords
-influenced by wave processes- increase in wave height and intensity due to rising temperature
-Valley sides influenced by sub-aerial processes- biological and chemical weathering increasing due to rising temperature (Van Hoff’s Law)- could increase mass movement- reduction in steepness of valley sides
-Increased rate of erosion if sea level rises further- estimated 0.6m rise in next 100 years
-marine erosion, but only affects the entrance of the fjord
-in the past, during ice age, when sea level fell, increased vertical erosion- river rejuvenation
Shingle beaches- affected by LSD, increase sea level rise, increase wave energy, more movement of sediments
Explain river rejuvenation
Before ria forms
During ice age when sea level fell, there is an increase in potential energy, which increased the rate of vertical erosion of the valleys, leading to steeper gradient and deeper river valley
