Exam questions for physical geography Flashcards
Assess the extent to which the global distribution of tectonic hazards can be explained by plate boundary process (12)
+To a great extent
+Most earthquakes are found at tectonic plate boundaries
+70% of earthquakes occur at the ‘ring of fire’ in pacific ocean
+Convergent or conservative boundaries generate most powerful EQ’s
+e.g San Andreas Fault
HOWEVER there are intra plate EQ’s (hotspots), and can occur old fault lines
+Tsunamis, 90% of all events occurring within the Pacific Basin
+generated at subduction zones
+Japan Taiwan Island arc, South America (25% of Tsunamis recorded here)
+Volcanoes occur at subduction zones and also constructive margins
+With the exception of hotspots (explain theory) e.g Hawaii
Assess how strategies to modify the event can reduce the impacts of tectonic hazards (12)
Disaster preparation & response
+Drills, education, warning systems and emergency kits
+Can have huge impact, less dependent on countries wealth
+E.g Japan, rapid response of 13,000 troops in China 2008
+HOWEVER inequalities still prevail,
E.g Anak Krakatau 2018 tsunami’s warning system not working, limited budget
Land use zoning can have the most significant impact (BEFORE hazard)
+ Removing people from dangerous areas prone to liquefaction etc
+ (we have seen the impacts in Haiti 2010, 2 million made more vulnerable due to informal housing)
+316000 lost their lives
+However this is not always possible , corruption in govt, Haiti EQ was unavoidably intense
+Aseismic Buildings, Tsunami walls (cross bracing, counter weights, deep foundations)
+In Japan 75% of buildings constructed with EQ’s in mind
+However need strict regulations and well developed economies
assess the importance of tectonic hazard profiles in understanding the severity of impacts resulting from earthquakes
+Hazards profiles help govts prepare:e.g
Magnitude, speed of onset, areal extent, predictability & frequency
+ HOWEVER magnitude doesn’t always = impact
+Doesn’t consider economic/human losses e.g Iceland = EU economy losing $5 Billion & Haiti deaths
+Japan’s 2011 EQ was mag 9, Haiti was mag 7
+Hazard profiles are flexible, easy to compare
+Visual and color coded, countries can identify at risk areas and can implement strategies (Management/ adaption)
+HOWEVER has no numeric scale, subjective, open to interpretation.
Assess the significance of mantle convection to the theory of plate tectonics (12)
Significant- Originally Wegener’s continental Drift theory- purely observational
+Arthur Holmes came up with theory of convection currents, which explained slab pull (magma cools at crust, becomes dense and sinks = volcanoes + EQ’s
(Subduction processes and benioff zone)
Convection currents also explain Volcanic hot spots
+Radioactive elements in core = plume = volcano chains
Assess why the economic losses and people affected by natural hazards have generally risen over time whereas the number of lives lost has fallen (12)
Increasingly affluent and urbanised world.
+More economic loss from property and infrastructure e.g Japan, but well developed disaster plans
+More people = greater displacement, evacuation of 47000 people
+Greater demand for infrastructure/ energy- Fukashima power plant case study
Increasingly globalized world- Iceland’s Eyjafjallajokull disrupted air travel = economic loss.
+ 100,000 flights cancelled, airlines lost $1.7 billion
Impacts would not be so great if world wasn’t so interconnected
(However does not explain less deaths, as there were no fatalities anyway)
Climate change and frequency of hydro-meteorological storms
+Philippines is a multi hazard zone
+Densely populated and poor infrastructure
+By 2040, El Nino events will be more frequent
+Could result in tech investment and disaster planning for the future = less deaths. (adaption despite inevitable impacts of climate change)
Evaluate the extent to which rates of coastal recession and stability depend on lithology (20)
Lithology is crucial- but human factors and sub areal processes are also at play
Geological are most significant- igneous withstands hydraulic action- interlocking crystals. Few weaknesses
e.g North of Scotland erodes 0.1cm per year
HOWEVER newly formed volcanic islands can erode 40m per year (though few select cases and igneous is generally resistant)
Sedimentary is clastic, heavily jointed, weak.(sandstone limestone) East coast of the Isle of Purbeck, headlands can be seen where coastal recession is slower, and the surrounding sedimentary rock has eroded quicker into bays.
E.g Holderness boulder clay erodes 2-10m per year
HOWEVER older sedimentary is more compact, deeper in the ground, and resistant.
Overall rock type plays a crucial role in determining recession
Sub Areal processes- freeze thaw weathering.
Expands in volume by 9% widening cracks, making rocks with fissures more vulnerable. HOWEVER relatively rare in UK, more in colder regions
Vegetation can lead to rock fall. HOWEVER lithology is underlying factor, weathering wouldn’t impact if the rock is resistant.
Human factors- hard/soft engineering reduce recession.
4.7km long wall in Bridlington, Holderness
HOWEVER defences can be weakened over time from hydraulic action.
Soft engineering may not have long lasting impacts, longshore drift limits the effect of beach nourishment.
Geology plays a larger role, depending on the rock type defences may not even be needed.
Evaluate the view that coastal flood risks are increasing mainly because of rising sea levels (20)
Eustatic changes- sea level change in respect to already low lying land.
Kiribati in the Pacific is 0.5m above sea level.
Sea levels predicted to rise by a metre by 2100 IPCC
Islands could be flooded by 2050
HOWEVER flood risk already there without sea level rise due to subsidence (Bangladesh)
Saturation of top soil layer
Rising sea levels can also cause vegetation to die.
Salt water contaminates fresh water sources and vegetation- loss of natural barriers.
HOWEVER human induced factors may be a greater reason- clearing of mangroves in Sri Lanka for shrimp farming.
Deforestation in Bangladesh increases speed of run off into rivers after monsoon periods- high saturation- exacerbates risk- takes longer to drain
80% of Bangladesh is a flood plain
Urbanisation is creating the flood risk
Explain the process of mass movement (6)
Block/rockfall
Occurs on slopes on >40 degrees where a fragement of rock breaks away and drops vertically/ bounces downslope
Initiated by: Marine erosion (abrasion, hyddraulic action, undercutting cliff)
South Dorset coast 2013 80m section of chalk cliff collapsed
Rotational slumping
Slower than rockfall, occurs on unconsolidated, weak material, water adds weight and lubricates bedding planes
A landslide is the downslope movement of blocks of rock down a slip plane, maintaining contact with the cliff surface throughout.
Released by mechanical weathering of well jointed rocks, (e.g. carboniferous limestone). Gravity then pulls the loosened block down the bedding plane
Explain the formation of a cuspate foreland
Longshore drift from opposing directions converge at the boundary of two sediment cells, forming a triangular shaped headland.
Currents pull the sediment out to sea forming this shape.
Dungeness has a 11km cuspate foreland
Evaluate the extent to which rates of coastal recession and stability depend on lithology
To a great extent as lithology ultimately determine how resistant a rock is to whatever process affecting it. Other factors can contribute including geology, weathering and subsequent mass movement as well as sediment cells and human defences.
Lithology is the greatest factor affecting recession and stability.
It affects stability because the composition of rocks differ. Crystalline vs clastic.
North Coast of Scotland/ outer Hebrides - erosion is at 0.1m per year,
Characterised by hard rocky coasts like in Cornwall’s Chapel Perth.
HOWEVER geology may have a more direct role in determining recession? Faults, bedding planes, dips, folds - e.g. many features on the Jurassic coast (Old Harry’s rocks)
Sub Areal processes- freeze thaw weathering.
Expands in volume by 9% widening cracks, making rocks with fissures more vulnerable. HOWEVER relatively rare in UK, more in colder regions
Vegetation can lead to rock fall. HOWEVER lithology is underlying factor, weathering wouldn’t impact if the rock is resistant.
Human factors- hard/soft engineering reduce recession.
4.7km long wall in Bridlington, Holderness
HOWEVER defences can be weakened over time from hydraulic action.
Soft engineering may not have long lasting impacts, longshore drift limits the effect of beach nourishment.
Geology plays a larger role, depending on the rock type defences may not even be needed.
referring to examples, explain the problems involved in classifying coastlines (8)
-Coastlines can be classified in 4 main ways, their geology, level of energy, balance of deposition and erosion, and changes in sea level.
The main problem with classifying coastlines is that many coastlines have features that are common for a mixture of both low energy coastal environments as well as higher energy environments.
For example, the rocky coastline along Cornwall also has land-forms such as beaches and estuaries that are usually associated with environments where deposition is more common.
-A further reason it is hard to classify coastlines is due to how coastlines often change depending on factors such as the seasons and climatic conditions, that can play a large role in the processes present at any given time. For example, the Holderness coastline is mainly a low energy environment through most of the year, however often experiences high energy storm conditions during the winter and so short term erosional processes occur, with the geology present then also creating headlands at the chalk cliffs at Flamborough Head.
This can also be seen in Cornwall which although usually experiences high energy and powerful waves from the Atlantic, estuaries (usually associated with low energy deposition coastlines) still form in more sheltered areas. It can also be said that defining coastlines to be more submerging or emergent is also complex, with often different landforms occurring and again at times these just being temporary and short term.
