Hazards 🔥

Question 1

Constructive plates

Answer 1

2 plates moving apart leaving a gap in middle for magma to rise up through. Earthquakes occur here e.g. Mid Atlantic Ridge. Ridge valleys also form as land falls into place more easily e.g. East African rift valley

Question 2

Oceanic crust

Answer 2

6-12km thick, about 200 million yrs old (+ still forming). Contains different types of basalts

Question 3

Continental crust

Answer 3

30-70 km thick. 4 billion yrs old (oldest). Layer of granitic, sedimentary and metamorphic rocks.

Question 4

Destructive plates

Answer 4

Oceanic plates descend below less dense continental plate. As plate descends it melts due to friction with the continental plate, forming hot, liquid magma. Magma rises up throigh cracks to form volcanoes at surface. e.g. marine trench or island arcs

Question 5

Conservative plates

Answer 5

Exist where 2 plates do not directly collide but slide past each other along a fault (weakness). Earthquakes occur e.g. San Andreas fault in California

Question 6

Park model of hazard response

Answer 6

Considers how standard of living & economic status of an area changes after an event

Question 7

Slab pull

Answer 7

At subduction zones gravity ‘pulls’ the oceanic plate down into the mantle. This destroys crust material & keeps earth in shape. Ridge push is opposite of this

Question 8

Paleomagnetism

Answer 8

Rocks having parts of metal in them (magnetism) which goes to North (the direction of magnetism). This can flip however in a North/south change.

Question 9

Oceanic - oceanic

Answer 9

Denser if 2 plates, 1 moves more quickly so is easily sub-ducted. Risk of tsunamis as this doesn’t happen on land.

Question 10

Oceanic - continental

Answer 10

Sinking of the denser oceanic crust below continental is called subduction. Destructive margins are some of the most seismically active zones. South American plate sinks to 6km.

Question 11

Continental - continental

Answer 11

Lower density than atmosphere. Forms largest food mountains on earth.

Question 12

Lithosphere

Answer 12

Coolest part of earth. It’s rocky & rigid outer part of earth.

Question 13

Asthenosphere

Answer 13

Below lithosphere- denser, weaker layer (100km)

Question 14

Stratosphere

Answer 14

Layer of atmosphere, 2nd layer as you go up.

Question 15

Mitigation

Answer 15

Actions taken to reduce severity, or painfulness of something.

Question 16

Adaptation

Answer 16

Action or process of taking appropriate action to minimalise damage, taking advantage of opportunities that may arise.

Question 17

Where are volcanoes found?

Answer 17

• Mainly located along plate boundaries or along coastlines. Some are found on land where earthquakes occur
• constructive boundaries along mid-ocean ridge around Pacific the oceanic plate is being subducted and melted in the Benioff zone
• occur in areas experiencing more seismic activity

Question 18

Shield volcanoes

Answer 18

Gentle slopes & a wide base, frequent eruptions of basic lava flowing at high speeds and for long distances before cooling. Usually non-violent eruptions, non-viscous lava, found at constructive boundaries.

Question 19

Composite volcanoes

Answer 19

Steep side with a distinctive cone shape, explosive eruptions if lava and ash. Layers of ash & lava (tephra). Viscous lava builds up but doesn’t flow far. Found at destructive plate boundaries.

Question 20

El Niño

Answer 20

A climate cycle in the Pacific Ocean with a global impact on weather patterns, caused by plate friction and by a release of seismic energy. Caused by eruptions or underwater landslides. These winds can also lead to faster drying of vegetation.

Question 21

Eruption styles

Answer 21

Icelandic: low viscosity & highly effusive. May have water therefore phreatic.
Hawaiian: effusive, minor explosivity with fire fountain & low viscosity lava flow.
Strombolian: eruption was gas bubbles so eject tephra (ash & labilli).
Vulcanian: higher gas build up, high viscous lava (bombs).
Pelean: explosive eruptions with range of tephra with Nuee ardente (growing cloud) pyroclastic flows.
Plinian: Highly explosive, large eruption column (up to 45km) range of tephra and pyroclastic flows.

Question 22

Augustine volcano (first erupted Jan 11, 1994)

Answer 22

Located in southwest of Cook Inlet, erupted mainly due to its location in a chain of volcanic islands running parallel to the Aleutian trench. In 1988, prevailing winds in March meant ash spread far, a large section of the 1968 dome collapsed and formed debris. (A threat to the people). At least 11 avalanches occurred since!

Question 23

Richter scale

Answer 23

Measures how much the ground moves and energy release by an earthquake (based in fact).

Question 24

Mercalli Index

Answer 24

Based on opinion to it at the time.

Question 25

Coriolis effect

Answer 25

A violent rotating storm occurring at the mid-latitudes, forming between 50-30 degrees above & below the equator. The hurricanes move away from the equator and have more energy at the centre. Warm moist air is drawn upwards. Cooler, dry air is sucked downwards by the low-pressure centre. Spinning vortex is made up of high winds and heavy rainstorms, bands of thunderstorms. Powerful winds of up to 39-73 mph are created. Whereas in eye of the storm, wind speeds are only 320km/h. Tropical storms only occur when ocean is 27 degrees or above and light winds. Use aircrafts & drones to predict an event.

Question 26

Storm surge

Answer 26

Abnormal rise in seawater level during a storm. Typically develops in late summer months (July-august) and in northern hemisphere (Jan- feb). Eg Typhoon Haiyan

Question 27

Liquefaction

Answer 27

Processes which causes soil to behave more like a liquid than a solid during earthquaking. It occurs when loosely packed, water-logged sediment at or near ground surface lose strength due to strong ground shaking. Eg. Occurs beneath buildings and can cause damage during earthquakes.

Question 28

Hazard risk

Answer 28

Measures how natural hazards affect places in different ways.

Question 29

Wealth of an area

Answer 29

How places receive help. More assets & expensive assets are likely to be built in hazard prone areas.

Question 30

Lahars & mudflows

Answer 30

Created when water & volcanic ash mix. They can form as pyroclastic flows over concrete & can originate from heavy rainfall or melting snow above a volcano & reach speeds up to 50km/h on steep slopes. Usually associated with heavy rainfall.

Question 31

Tilt meter

Answer 31

Using the “slope angle” is a tilt meter used to measure changes in the slope of a volcanoes side. Animals behave differently to hazards (they know minutes/hours before an event occurs).

Question 32

Earths heat source

Answer 32

Earth was hot when formed. Solid particles, “planetesimals” condensed out of the cloud, thought to have stuck together and created the early earth. Bombarding planetesimals geared earth to a molten state. Earth is cooling now but very slowly, it makes convection heat in its interior to keep a steady temperature. Earths temperature is estimated to be around 5,000- 7,000 degrees.

Question 33

Volcanic gases

Answer 33

Gases have harmful effects on health of people nearby. Significant effects on global climate, invisible & denser than air. Can cause short-term effects in the climate. Eg Lake Nyos: surrounded by old lava flows & pyroclastic deposits. Threat to suffocation of people and respiratory problems & pollution.

Question 34

Lava flows

Answer 34

Formed at around 1200degrees of basalt & streams of molten rock. Can destroy roads & cause buildings to collapse. People killed by increased CO2 levels. Heat of the eruption melts glaciers & icecaps causing flooding. Leaves people homeless/ jobless, lack of basic needs.

Question 35

Pyroclastic flows

Answer 35

A dense, fast moving flow of lava, volcanic ash & hot gases move up to 200m/s. Causes blocked streams, death, flooding, Lahars. Eg: 1980 mount St. Helens in USA (killing 57 ppl)

Question 36

Mudflows

Answer 36

Formed when high amounts of rainfall or melting snow/ice mix with volcanic material. Severe social and environmental impacts with it flowing so rapidly and going long distances. Eg. Totumo, in Columbia, a 50ft high “mud volcano”.

Question 37

Ash fallout

Answer 37

Large quantities of ash are carried from an explosive eruption when gases dissolve in molten rock and escape violently into the air. Eg Icelandic 2010 eruption which caused respiratory problems and crops dying.

Question 38

Saffir-Simpson scale

Answer 38

A hurricane wind scale, a tropical cyclone intensity scale estimating potential property damage.

Answer 39

A hurricane wind scale, a tropical cyclone intensity scale estimating potential property damage.

Question 40

East African rift

Answer 40

Been forming for 30 million years. Currently 3500km for the Red Sea to Moazambique and is formed from 2 parallel rift branches.

Question 41

Wildfire

Answer 41

Any rural fire uncontrolled and spreading. Fires need fuel (gas, oil, wood etc)/ heat (solar, electrics or matches) and oxygen to form.