A level geography cards

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  • Created by: Tooth04
  • Created on: 09-03-22 16:40

1.4 C Tectonics

-Impacts of tectonic hazards varies considerably from time to geographical region, which mary vary from minor nuisance to major disaster. 

-Disaster is categorised by; a significant impact on a population or 10 killed or 100 affected.

-The impacts of earthquakes (p and s) are usually much greater than those of volcanoes.

-The concentration of volcanoes across narrow belts means minimal area and populations are exposed to such a hazard (below 1% are likely to be affected by volcanoes compared to earthquakes 5%). 

  • Economic impacts are proportional to land area exposed (earthquake wins out). However needs to be set against context;
  • level of development (region or country)
  • insured impacts vs non-insured
  • resilience of the population e.g. economic recovery post tectonic hazard.
  • degree of urbanisation and linked interdependence
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1.6 A

-The 'root causes' phase of the PAR model, the most important causes are those which have economic, demographic or a political foundation.

-In developing and emerging countries people tend to have less power over thier socio-political and physical environments than the more wealthy. As a result of this difference, risk vulnerability is greater for them.

  • This can be explained as:
  • -People in developing and emerging countries only have access to livelihoods and resources that are insecure and difficult. For example, working underpaid jobs due to the lack of economic growth as companies create jobs59% of Haiti's pop. lives under the national poverty line.
  • -Likely to be a low priority for governments interventions intended to deal with hazard mitigation due to lack of resources or corruption.
  • -People who are economically or politically 'on edge' lose confidence in their own knowledge and are more likely to rely on government help which may not be apparent. 
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2B.4 Constructive waves

-Constructive waves have a low wave height (less than 1m). Long wave length (up to 100m).

-They are gentle, flat waves with a strong swash (flow of water up a beach as the wave breaks) but weak backwash (flow of water down a beach as the wave breaks).

-The strong swash pushes sediement up the beach depositing it as a berm at the top of the beach. 

-Relatively gentle beach profile with the steep berm at the top of the beach means that most of the backwash percolates into the beach. 

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2.4B Destructive waves

-Destructive wave height of over 1m to 20m. They are common during storms.

-These waves have strong backwash that erodes beach material carrying it offshore creating an offshore ridge or bar. 

Depending on conditions, beaches experience both constructive and destructive waves over the course of time.

-Short term - Uk beach profiles change seasonally between winter and summer, when destructive dominate in winter and constructive dominate in summer. Plunging destructive storm waves can give way to swelling constructive waves leading to changes over the course of a day.

  • Long term changes in beach profile due to:
  • sediment supply changes e.g. terminal groyne sydrome
  • interference in sediment supply through coastal management affecting further down the coast.
  • climate change e.g. more frequent storms due to warmer waters increased 'winter' profiles. 
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2B.4 Erosional processes

  • -Hydraulic action - air trapped in fissures and cracks are compressed by the force of the waves against the cliff face, where the pressure gradually forces the cracks open so more air is trapped and greater force experienced in the next compression -  blocks of rocks are dislodged.
  • -Heavily jointed sedimentary rocks are affected, may be only process acting on very resistant igneous rock (basalt, granite).
  • -Abrasion - sediment picked up by the waves acting as a chisel against the rockface  and gradually wearing it down through removing small rock strata.
  • - Requires loose sediment such as pebbles so softer sedimentary rocks are more vulnerable.
  • -Attrition - acts on already eroded sediment as sediment in the waves collide around in the waves chipping fragments off. 
  • -Softer rocks are rapidly reduced in size and rounded by attrition.
  • Corrosion - solution by rainwater and spray from sea - mainly affects limestone whic is vulnerable to weak acids.
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2B.4 Coastal landforms

-Arch, Cave, Blowhole, Headland, Stack, Stump, Wave cut notch, Wave cut platform.

Most coastal landforms are most commonly found where the sedimentary rocks (sandstone, chalk) are with well-defined bedding planes and joints. Shales and clays are not competent enough to form many erosive features. 

-Wave cut notches are created by hydraulic action and abrasion, overhanging rocks that are undercut and become unstable and collapse creating a rockfall. Wave cut platform visible at low tide as a horizontal rock platform. 

Cave and blow hole formation is more common in areas weakened by the presence of a fault. Stacks may indicate more resistant areas of rock. 

The Old Man of Hoy is the UK's tallest stack at 137m high. 

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2B.5 Transportation processes.

-Usually sediment is transported along coastlines by currents, known as longshore drift. Longshore drift has a crucial role in coastal sediment cells.

-LS - wave crests approach the coast at an angle, the swash and the backwash follow different angles up and down the beach in a zig-zag pattern.

-Wave direction is caused by wind direction, although most coastlines have dominant prevailing winds.

-Traction - sediment rolls along, pushed by waves and currents - pebbles, cobbles and boulders.

-Saltation - sediment bounces along either due to force of water and wind - sand size particles.

-Suspension - sediment is carried in a water column - Silt and clay particles - make water appear muddy.

-Solution - sediment dissolved in water carried as a solution.

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2B.5 Depositional processes

-Swash-aligned - wave crests approach parallel to the coast, so there is limited longshore drift.

-Drift-aligned - wave crests break at an angle to the coast, so there is consistent longshore drift and elongated depositional landforms. ,

  • Deposition can occur through:
  • Gravity settling - when water energy becomes too low to move sediment and it is deposited.
  • Flocculation - where particles clump together through eletrical and chemical attractions and become large enough to sink e.g. clay. 
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2B.6 Weathering

  • Mechanical weathering:
  • Freeze-thaw - water expanding in cracks and fissures - any rocks with cracks and fissures.
  • Salt crystallisation - growth of salt crystals can exert a breaking force - porous and fractured rock e.g. sandstone, effect is greater in hotter and drier climates.
  • Chemical weathering:
  • Carbonation - slow dissolution of limestone and carbonate rocks due to rainfall.
  • Hydrolysis - breakdown of minerals to form new clay minerals due to effect of dissolved C02 and water.
  • Oxidation - addition of oxygen to minerals like iron contributing to mechanical breakdown - sandstones and shales etc contain lots of iron. 
  • Biological weathering:
  • Plant roots - trees and plants growing roots in cracks forcing the rocks apart.
  • Rock boring - species of clams and molluscs bore into rock and secrete chemicals that dissolve rock - carbonate rocks.
  • Weathering weakens rock making it more vulnerable to erosion and mass movement.
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6.2A Biological processes that sequester carbon

The carbon cycle works fastest at the surface of the ocean as gaseous exchange from the atmosphere into the ocean is happening here. Some dissolves into the water and some is pulled from the air.

-Ocean's surface contains phytoplankton that contain cholorphyll and sequester carbon through photosynthesis, where most of the carbon is re-released through respiration.

-The phytoplankton also use the carbon to create calcium carbonate shells, which add to the sediment at the bottom of the ocean when they die and sink - long-term store. 

  • Thermohaline circulation: 
  • phytoplankton are a part of a fragile ecosystem and require a constant supply of nutrients via ocean temperature and currents.
  • Warm water rises to the surface and is rich in C02 
  • Cold water sinks due to denisty and is less rich in C02
  • Pockets of warm and cold water move around the globe. 
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6.3B Terrestrial carbon

-Terrestrial primary producers sequesters carbon through the process of photosynthesis, green plants use solar energy to create biomass and take in carbon.

-Plants and animals respire which are the faster sections of the terrestrial carbon cycle, with rapid exchange of carbon between plants and the atmosphere. 

-Leaves, roots, dead organic material, decaying litter and residues contain carbon and are a part of a slower carbon cycle as they require decomposition or deforestation to release thier carbon. 

  • -Mangroves: 
  • found in tropical and sub-tropical tidal coasts along Africa, Australia, Asia and the Americas (tidal coasts have high tidal ranges and aren't dominated by waves). 
  • mangroves sequester 1.5 metric tonnes per hectacre per year.
  • contain thick layers of litter and anaerobic soil as they are submerged twice a day (minimal decomposition). 
  • removing 2% of global magroves would release 50 times the carbon sequestered naturally. 
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5.4 Meteorological / agricultural drought

-Meteorological drought is a shortfall in precipitation which increase the duration of a dry period. Leads to loss of soil moisture and decline in irrigation water supply --> desertification. 

Precipitation deficiency is usually combined with high; temperatures and winds, strong sunshine and low humidity which all increase evapouration. 

Deficiency can be caused by short term or long term; (ST) variations in atmospheric conditions, desiccation (removal of moisture) due to deforestation, (LT) El Nino events  climate change.

-Agricultural drought is a deficiency of soil moisture and soil water availiability brought on by meteorological drought which affects plant growth and reduces biomass. Soil moisture budgets can show more severe and protracted (longer than normal / expected) defecits. Leads to a decline in grounwater water supply due to reduced percolation from rainfall defecit, poor yields from rain-fed crops, failure of irrigation systems due to reduced supply and subsistence farmers requiring aid. Over-grazing can accelerate the onset or be a causation as plants don't replenish due to rainfall deficiency.

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5.4 Hydrological drought

Hydrological drought is a reduction in stream flow and groundwater levels due to rainfall deficiency and continued high rates of evapouration. 

Leads to marked salinisation through high evapouration rates drawing from the soil onto the surface and poor water quality through increasing residence timesand reduced flushing of water bodies due to limited flow. 

Salinisation affects ecosystems and biodiversity as it can be toxic and make areas uninhabitable. Also farmers are often forced to leave salinised areas due to lack of knowledge of farming salt water crops and believing the area is unuseable.

In 1973 Uk had to employ a minister of drought to deal with the srping drought to manage the crisis.

In NE Brazil there are no permanent rivers and limited shallow water stores due to seasonal variability in rainfall. Leaves rural dwellers with limited, poor water supplies that lead to ill health and high cost of transport to get resources in. 

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Famine or Socio-economic drought

The fourth type of drought, famine drought, is often a causation of the other types of drought. 

Rainfall deficiency causes agricultural failure that leads to famine that have severe social, economic and environmental impacts (Horn of Africa case study). This is categorised by a food defecit that can decimate rural communities and lead to mass displacemnt through loss of livelihood.

As populations grow thier demand for water increases, at some points natural variability in climate can cause temporary decline and supply snd strores aren't replenished - short term.

Long term susceptibility to drought brought around by ENSO cycles and climate change due to global warming e.g. drier climates introduced. 

Areas severly affected by drought has doubled in the last 30 years - 30% of global land mass now experiences severe drought. Droughts are known as creeping hazards and have long periods of onset so can be difficult to decipher between droughts and dry periods.

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Case study: Horn of Africa

  • -The Horn of Africa or the Somalian peninsula is the eastern side of the continent containing Somalia, Ethiopia and Kenya currently experiencing thier 3rd drought (April 25th 2022) in 11 years.
  • -Over 15 million people are experiencing acute food insecurity (a person's inability to consume adequate food volume that places thier life in immediate danger) due to drought - a causation of three poor below average rainfall seasons .
  • -OCT-DEC 2020, MARCH-MAY 2021, OCT-DEC 2021, as they brace for a potentially fourth consecutive below average rainfall season.
  • ENV- 1.5 million dead animals in Kenya, with 1.5 million livestock dead in Somalia. 
  • ENC- enconomic challenges, below-average harvests and rising international prices (UKR VS RSA) has led to food baskets rising 66% in Ethiopia and 36% in Somalia.
  • SCL- 15 million people are experiencing acute food insecurity, 2.9 million displaced in Somalia.

-2010-2011 , 2016-2017 and now 2020-2021, consecutive droughts has reduced families abilities to recover between shocks despite more than 6.4 million being reached by humanitarian aid.

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2B.7 Long term sea level changes

Sea levels can change daily through high and low tides altering local sea level, atmospheric pressure where low air pressure cause a slight rise in sea level and wind pushing water towards the coast raising sea and wave height. 

  • Eustatic and isostatic falls create emergent coasts.
  • Glacial periods where ice sheets lock evapourated water as ice leading to global sea level fall (eustatic)
  • Post-glacial isostatic adjustment as melted ice sheets that once caused crustal sag so the land slowly rebounds lifting land surface out of the sea (isostatic)
  • Eustatic and isostatic rises create submergent coasts.
  • At the end of glacial periods ice sheets melt causing global sea level rise and global temperature increase causes thermal expnasion raising sea level height (eustatic).
  • Heavy deposition of sediment (accretion) can sink land, especially at large river deltas where the weight of the sediment can cause crustal sag (isostatic).
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