EQ3 Flashcards
1
Q
Pattern of temperature change over the last million years
A
- Over the last million years the Earths temperature fluctuated
- During the half 500k years the Earth had 5 intense glacial periods lasting 60-100k years each
- This alternated with shorter warmer periods lasting 2-25k years
- The Earth is currently in an interglacial periods that reached modern temps 12k years ago
2
Q
Types of sea level change
A
Isostatic - change in land level:
- When ice is kms thick it’s heavy and pushes land it’s sitting on downwards
- Areas under ice are depressed but areas further away are uplifted
- Land rebounds up or sinks when ice age ends
- Scotland is rising and SE England is sinking
Eustatic - A change is sea level:
- Much of the worlds water is held in ice sheets, ice caps & glaciers in an ice age
- Sea levels fall
3
Q
Contemporary sea level change
A
- Climate warming leads to sea levels rising
- Glaciers in Himalayas melt and polar ice sheets incr the water in the ocean store
- IPCC - Intergovernmental Panel Climate Change attributes 50% sea level rise from 1920-2010 to ice sheets melting
- Thermal expansion of existing ocean water as temps rise
- 94% of incr heat energy is transferred to oceans
- IPCC attributes 40% of sea level rise to this
4
Q
Physical factors affecting rates of coastal recession
A
- Geology e.g Boulder clay on Holderness
- Sub aerial processes e.g weathering
- Fetch e.g destructive waves on Holderness
- Erosion
5
Q
Human activities on Nile Delta affecting coastal recession
A
Dams:
- Construction of dams e.g Aswan High Dam reduced sediment flow downstream to the delta
- Before the dam there was 100mill tonnes of sediment load p/a now 10mill
- Less sediment = more erosion as sediment cannot reduce wave energy anymore and lead to loss of habitat & less coast stabilisation
Urbanisation:
- Construction of buildings in cities expanding e.g Cairo over 20mill people
- Removal of natural vegetation and soil
- Increases runoff and erosion
6
Q
Flood risk on Bangladesh
A
- Bangladesh is the world’s most densely populated country 174.7million people 2024
- Deforestation due to incr population
- Bangladesh lies on 3 major rivers Brahmaputra, Meghna and Ganges
- Storm surges Cyclone Sidr 2007
- 3406people dead
- 1518942 houses destroyed
- 223km hr wind speeds
- Bangladesh islands sunk by 1.5m in last 50 years
- Reason is drainage and clearance of 50large forested islands for rice farming
Mangroves:
- Essential to marine freshwater and terrestrial biodiversity, they stabilise coastlines, collect sediments and provide a home for fish
- They absorb wave power = protection
- 71% of mangroves are retreating by 200m per year caused by erosion + human action
- Sri Lanka protects all of its mangrove forests
- During the Indian Ocean tsunami in 2004, only 2 people died it mangrove protected areas
- But 6000 people died where mangroves had been removed
7
Q
Climate Change Impacts: More storms
A
- In North Atlantic, average n.o storms p/a was 11 with 6 becoming hurricanes
- Now average is 16 storms with 8 becoming hurricanes
- This increase related to rise in North Atlantic sea level temperatures
- IPCC predicted by 2100, hundreds of millions of people forced to abandon many coastal zones world wide
- Sea levels rise = more storm surges
- E.g rising sea levels in 2012 increased Hurricane Sandy in USA 106 deaths and $65bn damage
