The Restless Earth Flashcards
Describe the problems, uses, and adaptations to life in a location in fold mountains that you have studied.
Livignio, Italian Alps
- Problems: Isolated, thin soils, cold, inaccessible
- Uses: Transhumance, HEP, mining, skiing 90% local economy
- Adaptations: Valley farming instead of transhumance, hairpin bends, snow sheds, avalanche gates, controlled avalanche explosions, tunnels linking to Swiss road network
Name, locate, and describe the causes of a tsumani you have studied.
Japanese Tsunami, Sendai, Japan - 11th March 2011
- Megathrust 0.9 quake between Pacific and Philipines plate. Destructive subduction.
- Epicentre was in Sendai, although focus was in ocean
- 10m high tsumani wave formed
Describe the effects of a tsunami you have studied
Japanese Tsunami, Sendai, Japan - 11th March 2011
- Japan sank by 1m
- 15,000 dead
- Yen fell sharply + Japanese stock exchange crash
- Infrastructure destroyed
- Fukishima Power Plant meltdown
- Minamisanriku 90% destroyed
- 10m high sea wall overwhelmed in Ofunato
Describe the short responses to a tsunami you have studied
Japanese Tsunami, Sendai, Japan - 11th March 2011
- Text + news alerts on TV + radio
- Army mobilised
- International aid from charities (Oxfarm, Red Cross)
- Fukishima exclusion zone set up
- Fukishima 50 sent in to prevent further disaster
Describe the long term responses to a tsunami you have studied
Japanese Tsunami, Sendai, Japan - 11th March 2011
- Rebuilt coastal towns - Sendai + Ofunato
- Fukishima shut down forever + covered in concrete to prevent further leaks
- Infrastructure rebuilt within 9 months
Describe the causes of a volcanic erruption you have studied
Mount. St. Helens, Cascade Ridge, Washington, USA - 18th May 1980
- Composite volcano blocked with thick andersite lava plug
- Lava rose through volcano but couldn’t escape. Created a bulge which grew 10m per day.
- Destructive subduction triggered earthquake which led to lateral blast
Describe the effects of a volcanic erruption you have studied
Mount St. Helens, Cascade Ridge, Washington, USA - 18th May 1980
- 27km wipeout zone
- Pyroclastic flows
- 57 killed
- Flights grounded
- Ash column miles high
Secondary:
- Lahars
- Ash up to 10m deep in some places
Describe the short term responses to a volcanic erruption you have studied
Mount St. Helens, Cascade Ridge, Washington, USA - 18th May 1980
- USGS monitored erruption + bulge
- 8km exclusion zone set up yet ignored
- Emergency services + army mobilised
- National Emergency declared in NW states
- Helicopters search + rescue
- 2 millions gas masks given out to all residents of NW
- Residents advised to stay at home
Describe the long term responses to a volcanic erruption you have studied
Mount St Helens, Cascade Ridge, Washington, USA - 18th May 1980
- Spirit Lake + Toutle River cleared and dredged
- USGS set up COSPEC, GPS, tiltmeters, and seismographs
Describe the positive impacts of a volcanic erruption you have studied
Mount St Helens, Cascade Ridge, Washington, USA - 18th May 1980
- 2 million visitors per year
- Soil fertility increased
- New pine forests grown
Although Mountain no longer has beautiful cone-shape.
Describe the causes of an earthquake in an MEDC you have studied
Kobe, Japan - 17th January 1995
- Destructive subduction
- Nojima Fault under CBD
- Shallow focus
- Magnitude 7.2
Describe the effects of an earthquake in an MEDC you have studied
Kobe, Japan - 17th January 1995
- 5,500 dead + 30,000 injured
- Infrastructure collapsed in older suburbs (roads blocked)
- 2 tonne typhoon-proff roofs ‘pancaked’
- Liquifaction in Osaka Bay area (reclaimed marshy land)
- Port out of action
- Hanshin Expressway collapsed
- Secondary: Fires
Describe the short term responses to an earthquake in an MEDC you have studied
Kobe, Japan - 17th January 1995
- Rapid responses
- Emergency services + 3000 army troops sent to suburbs + Hanshin Expressway
- Sniffer dogs
- ‘Jaws of Life’ move rubble + rescue
- Thermal imaging equipment used
Describe the long term responses to an earthquake in an MEDC you have studied
Kobe, Japan - 17th January 1995
- Retro-engineering (Osaka Bay Tower)
- 15m steel rods + shock absorbers on Hanshin
- CBD rebuilt within a year
- 80% of port rebuilt within a year
Describe the causes of an earthquake in an LEDC you have studied
Port au Prince, Haiti - 13th January 2010
- Conservative boundary
- Shallow focus
- 7.0
- Epicentre directly beneath CBD
- Densely populated
- Unprepared + building laws ignored
Describe the effects of an earthquake in an LEDC you have studied
Port au Prince, Haiti - 13th January 2010
- 250,000 dead
- Infrastructure collapsed
- 1 in 3 buildings collapsed
- Jail break + 4,000 escaped
- Secondary: Cholera from UN soldiers + typhoid
Describe the short term responses to an earthquake in an LEDC you have studied
Port au Prince, Haiti - 13th January 2010
- Uncoordinated
- Emergency services not mobilised - 1 private ambulance
- People left to search themselves
- Government collapsed
- Hospitals overwhelmed - many fled to Dominican Rep. for care
- Dead left on streets
- Country inaccessible for aid - port 5 days, airport 48 hours
Describe the long term responses to an earthquake in an LEDC you have studied
Port au Prince, Haiti - 13th January 2010
- 1.5 million in temporary accommodation a year later
- City not rebuilt
- No future defenses put in place
What are seismic waves and what are the three types?
The energy released by an earthquake
P waves
S waves
Surface waves
Describe the three types of seismic wave
- Primary waves - fastest + shake earth back + forth
- Secondary waves - slower + shake earth laterally (side to side)
- Surface waves - Slowest + arrive last. Travel near to surface and are the most devestating. Can be longitudinal or transverse
What is magnitude?
The amount of energy released by an earthquake
Usually measured on the Richter scale
What is the Richter scale?
Logarithmic scale with each unit representing a 10x increase in strength
Scientific + reliable
But doesn’t measure effects of earthquake
What is the Mercalli scale?
12 point scale measuring the effects of a seismic event. Is based on people’s observations
Is subjective and not scientific
But does show effects
What are the three Ps?
- Prediction - Attempt to forcecast event (where + when) based on current knowledge (e.g. USGS)
- Protection - Constructing buildings so they are safe to stay in + will not collapse (e.g. Torre Major, Mexico City)
- Preparation - Organising events + drills so people know what to do in the event of an emergency (e.g. FEMA)
What is a tsunami train?
The series of waves that hit the coast during a tsunami
What is the difference between focus and epicentre?
Focus is the point in the crust where the pressure is released + the seismic waves come from
Epicentre is the point on the crust directly about the focus. It recieves the highest amount of energy from the earthquake
What are hot spots?
Points on the crust where plumes of magma rise, weakening the crust
They are away from plate boundaries
Describe oceanic crust
- Newer - less than 200 million years old
- Denser than continental, can subduct
- Can be renewed + destroyed
- Softer + more malliable
Describe continental crust
- Older - over 1500 million years old
- Less dense, cannot subduct
- Cannot be renewed + destroyed
- Hard + brittle - crumples to make fold mountains
What are ocean trenches?
Deep sections of the ocean created by an oceanic plate subducting underneath a continental one
The Mariana Trench in the Pacific is the deepest place on Earth and is caused by two oceanic plates being subducted
What is a lahar?
A secondary effect of a volcanic event
Ash mixes with rainwater or snowmelt to form huge mudflows than can travel up to 90mph
Explain how volcanoes occur at destructive margins
- The oceanic plate is subduted beneath the continental plate as it is denser
- As it moves into the mantle, it melts and forms magma and gases which force their way to the surface
- This magma and gas rises and breaks through the continental plate, creating a vent and eventually forming a violent volcanic erruption
- Volcanic bombs are created from the previous lava dome forced off by the pressure
Describe the formation of fold mountains
- Formed at destructive collision boundaries where two continental plates collide.
- Sediment is deposited on the ocean floor in goecynclines.
- Over time it is compressed and forms sedimentary rock
- As the two plates collide, the layers of rock are forced upwards, creating fold mountains
- Minerals are also forced up during the collission
Explain how volcanoes form at constructive plate boundaries
- Two oceanic plates move apart, exposing magma from the mantle which rises and reaches the ocean bed
- It then cools and forms rocks and underwater shield volcanoes
- As the plates continue to move apart over time, more magama is exposed and builds up, eventually reaching the surface of the sea
- This then forms an island or a shield volcano on land
Describe how earthquakes occur at conservative plate margins
- Conservative boundaries occur where two plates slide past each other
- Friction causes them to get caught on each other
- Over time, pressure builds up until it is suddenly released and they jolt past each other
- This is an earthquake
Describe the formation of ocean trenches
- Occur at destructive subduction boundaries
- As the oceanic plate is subducted beneath the continental plate, it creates a deap trench
- Part of the continental plate is also dragged under by the oceanic plate as subduction occurs
- The deepest trenches (such as the Mariana Trench) are formed when oceanic-oceanic subduction occurs
Describe how composite volcanoes are formed
- Occur at destructive boundaries
- Magma builds up in magma chamber beneath the base. This is added to as oceanic crust melts as it subducts at the margin
- As the magma rises through the main vent, it forms a lava dome as it very viscous (andersite)
- Eventually, the pressure becomes too great and the dome is blown off in an explosion of ash, gas, lava, and debris
- The neck of the volcano is cleared, allowing lava to flow out
- As lava flows down the sides of the volcano, it cools, forming more layers + sides of the volcano. Ash settling on the lava also causes the sides to build up
Draw and label the features of a composite volcano
- Main vent
- Secondary vent
- Lava dome
- Magma chamber
- Volcanic bombs
- Pyroclastic flows
- Ash column
- Layers of ash + lava forming steep sides
- Crater
- Steep sides, narrow base
- Andersite lava (viscous)
Draw and label a diagram of a shield volcano
- Summit caldera
- Gentle, sloping sides
- Magma chamber
- Main vent
- Layers of ash + lava forming sides
- Flank eruption
- Basalt lava (not very viscous)
What is a supervolcano
A volcano that produces at least 1000km3 of material when it errupts
Describe the features of a supervolcano
- Caldera - Depression/crater of the volcano marking the collapsed magma chamber
- Fissures - Lines of weakness that allow magma to escape
Describe the formation of a supervolcano
- Supervolcanoes are found on hotspots
- Yellowstone was created by a super erruption 640,000 years ago
- Before the erruption, magma flowed into the magma chamber.
- Too much pressure in the magma chamber caused fissures to form and gas and ash to be ejected out of them in a massive super erruption
- After the erruption, the land collpased into the magma chamber, forming a caldera
