Hazards Flashcards
What is subduction
A geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced to sink due to differences in density
What are the characteristics of an oceanic plate (4)
- Younger (younger than 200m years old)
- Thinner (5km)
- Denser/heavier
- Can be both created and destroyed
What are the characteristics of a continental plate (4)
- Older (up to 4 billion years old)
- Thicker (30-70km approximately)
- Less dense
- Can’t be created or destroyed
What is the meeting point of 2 tectonic plates called
A plate boundary
What are the seven primary tectonic plates
- African
- Eurasian
- North American
- South American
- Pacific
- Indo-Australian
- Antarctic
note i dont think you will need to know these so dont worry about learning them, this card is only there in case this helps to add a nugget of information e.g. in an 8 marker
What is deggs model
A Venn diagram with hazards as one part and vulnerable population as the other - the meeting point is disaster
What is a hazard
An extreme event that threatens people, their property and settlements
When does a hazard become a disaster
When the hazard causes widespread destruction to property and human lives
What is risk
The probability of an event happening and the scale of its possible damage
What factors affect the risk of a hazard (6)
- How easily the hazard was to predict
- The fréquency of the events
- The level of mitigation
- The severity of the hazards
- The level of infrastructure
- The education level of the people on how to cope with the hazard
What is a geological hazard
Volcanic eruptions, earthquakes
What is a climatic hazard
Tropical storms
How thick is the outer core
2200km
How thick is the crust and what is it made of
0-70km - granite and basalt
How thick is the mantle and what state is it
2900km, solid but flows
How thick is the inner core, what is the composition and what state is it
1270km
Solid iron and nickel
Give some characteristics of oceanic crust (4)
- Newer (less than 200m years old)
- Denser
- Thinner -> 5km
- Can subduct
Give some characteristics of continental crust (4)
- Older (1.5 billion years old)
- Less dense
- Thick -> 30km
- Can’t subduct
What is the lithosphere
Top 100km of the earth (i.e. crust and top part of the mantle) that makes up the earth’s tectonic plates
Describe the distribution of earthquakes and volcanos worldwide
- Uneven distribution
- Mostly on plate boundaries
- Ring of fire
- Volcanic hot spots can occur away from plate boundaries
- Earthquakes away from boundaries can be caused by human activity e.g. fracking
What is a constructive plate boundary and what is formed
2 oceanic plates moving apart
Creates volcanoes and small earthquakes
What is a destructive plate boundary and what is formed
Oceanic plate subducting under a continental plate.
Powerful earthquakes and explosive volcanoes formed
What is a collision plate boundary and what does it cause
2 continental plates colliding
Causes powerful earthquakes and creates fold mountains
What plate boundaries make strato volcanoes
Destructive
How is a strato volcano formed at a destructive plate boundary
The oceanic plate subducts under the continental plate. The oceanic plate then melts. The newly created magma rises to the surface and is erupted, over time forming a volcano
What is slab pull
The force exerted by a subducting oceanic dense oceanic plate, pulling the rest of the plate down with it
What is ridge push
The oceanic ridge pushes down on the plate boundary, therefore causing the plates to move apart to make room for the oceanic ridge. A bit like how balancing two books on each other, then putting weight on the top will cause them to move apart.
What plate boundary forms a shield volcano
Constructive
How is a volcano formed at a constructive plate boundary
The plates move apart, then magma rises through this weak spot in the crust and is extruded in eruptions, forming volcanoes when it solidifies to lava
What is the difference between magma and lava
Magma is in the mantle, lava is on land
What are some characteristics of shield volcanoes
- Basaltic lava
- Low viscosity (very runny)
- Effusive eruptions
What is the astenthosphere
The upper part of the mantle that isn’t in the lithosphere - acts as a lubricant for the tectonic plates to move on
How do convection currents move plates
The continuous force that is applied on the plates by the moving magma pulls them apart
How are convection currents formed
Hot magma rises, then cools as it goes away from the core, so again falls. This will then repeat
How can hazards be classified (4)
- Geological (e.g. volcano, earthquake)
- Climatic (e.g. tropical storms)
- Biological
- Technical
What is the lava flow of the volcano
Slow, can be outrun, depending on viscosity. Essentially melted rock
What is the pyroclastic flow
Hot cloud of gas, rock and ash that rushes down the mountain at up to 200mph and 800ºC
What is the tephra
Volcanic material deposited near the volcano
Describe the ash clouds created by volcanos
Can circulate around the upper atmosphere, disrupting planes. It is incredibly fine
What is volcanic lightning
When materials are ejected from the volcano they can go into the sky and gain electrical charge. This can produce lightning
What are volcanic tsunamis
Volcanic eruptions cause disturbances, which can displace lots of water and generate tsunamis close to the eruption
What gases are produced by volcanic eruptions (4)
- Sulphur dioxide
- Water vapour
- Nitrogen
- CO2
What are Lahars
Mudflows that occur when ash mixes with mud on the side of a volcano
What is glacier run
When icebergs melt on the side of a volcano and create a flood down the volcano
What are some benefits of living near a volcano (4)
- Heat from magma can be used for energy
- Lots of minerals like gold left by magma
- Fertile soil
- Tourism
How to monitor a volcano (5)
- Seismometers - measure earthquakes near eruptions
- Tilt meters - monitor change in landscape (swell)
- Monitoring gases - escaping from volcano - often an increase of sulphur dioxide before earthquake
- Measuring temperature - hotter before an eruption
- Statistics of past eruptions
What is a rift valley
2 conservative plates moving apart, creating new crust in the middle within a continental rift valley.
What scale measures earthquakes
Mercalli scale, or the Richter scale
What is the focus
The point under the surface where the tectonic plates slip due to the friction building up, causing an earthquake. This is where the earthquake is strongest
What is the epicentre of an earthquake
The point on the surface directly above the focus
How can earthquakes be predicted with tiltmeters
They show how the ground is moving and changing
What are p waves
Primary waves - they move faster than S waves. They send vibrations. Often go unnoticed without equipment
What are S waves
Secondary waves - more powerful, perpendicular to direction of wave travel is the direction of vibration (transverse).
Which type of waves causes the most damage in an earthquake
Love waves
Which can travel through liquids: p or S waves
S waves
Why are some places affected more by earthquakes than others (5)
- Building design “earthquakes do not kill people, buildings do”
- Strength of earthquake
- Preparation level
- Population density
- Speed of aid arrival
What advantages are there of living in areas prone to earthquakes
No obvious advantages
Where geographically do tropical storms form
5-30º north and south of the equator
What conditions are needed for a tropical storm to form (4)
- Over seas with over 27º temperature
- Low wind shear - not much variation in wind direction and speed
- Low pressure area
- Circular motion in the air
What is the Coriolis force
The force caused by the rotation of the earth tat encourages the rotation of a tropical cyclone
What are storm surges and how are they formed
Low pressure near the eye pulls the water upwards. Winds push this water towards the shore
What is the eye of the storm
The area in the centre of the storm where there is calm and there is no cloud cover
What wind speed must the tropical storm reach to be classified as 1. A tropical storm 2. A hurricane
- 34mph
- 74mph
What scale is used to measure hurricanes
Saffir-Simpson scale
What can a lack of development lead to in a tropical storm
Slow governmental response
Poorly built buildings will collapse
Worse resources for predictions
How to prepare for earthquakes
- Attempt to predict
- Earthquake proof buildings
- Education
Give some features of an earthquake proof building (4)
Shock absorbers in strong foundation
Automatic window shutters to prevent falling glass
Steel frames that can sway instead of breaking
Computer controlled weights on roof
What to do during an earthquake
- Do the earthquake drill
- Go to open areas
- Report missing people
Give some details about mount fuego
3rd June 2018
48km from Guatemala City
110 killed
1.7 mullion effected
Give some details of Kilauea
May 2018
No deaths
10,000 residents evacuated, some by helicopter
Describe the Nepal earthquake
-April 2015
-7.8 on Richter scale
-9000 deaths
- 1.4 million required food aid
Describe the Italy earthquake
August 2016
- 298 dead
- magnitude 6.2
- 4000 made homeless
- 3 am so many were asleep
- 50m euros worth of emergency government funding
Describe cyclone Idai
Mozambique march 2019
2.5m high storm surge
150mph+ winds
2.6m people affected
800+ died
Lack of access to food and basic services
What are the characteristics of a strato volcano
It is tall, steep sided, composed of alternating layers of lava and pyroclastic flow/ash deposits.
Explosive eruptions
