Chapter 5 - Hazards - Complete Flashcards
Define a hazard?
Something that’s a potential threat to human life or property
Define natural hazard?
A hazard caused by the earth and our atmosphere
Define geophysical hazard?
Caused by land processes
- Earthquakes
- Volcanic eruptions
- Landslides
- Tsunamis
Define atmospheric hazards?
Caused by climatic processes
- Tropical cyclones
- Storms
- Droughts
- Extreme hot/ cold weather
- Wildfires
Define hydrological hazards?
Caused by water movement
- Floods
- Avalanches
Define disaster?
When a hazard actually seriously affects humans.
What’s the difference between a natural hazard and a disaster?
A natural hazard is a volcano erupting in a deserted place but becomes a disaster when it affects people.
Define risk?
The likelihood that humans will be seriously affected by a hazard.
Define vulnerability?
How susceptible a population is to the damage caused by a hazard.
Define 5 factors that affect peoples perceptions of a hazard? W R E P E P
- Wealth = rich people afford to move house.
- Religion = view hazard as act of God.
- Education = More education better understanding of risks.
- Past experiences = People live in hazard-prone areas, adapt and know circumstances.
- Personality = People fear hazards/ others think they’re exciting.
Define 4 things governments try to do to reduce their vulnerability of a hazard? P P P F
- Preparation to reduce its magnitude. Building flood defences. Cost risk sharing.
- Prediction of hazard, when, where a hazard will occur.
- Protection of property.
- Fatalism - accept the hazard cannot be avoided.
Define the Park Model?
Shows the different phases of response to a hazard.
Define the 5 stages in the Park Model? P D D R R R
- Pre-Disaster
- Disruption
- Relief
- Rehabilitation
- Reconstruction
Define PRE-DISASTER in the Park Model?
Before the event, situation is normal.
Define DISRUPTION in the Park Model?
During & directly after the hazard occurred, destruction of property, loss of life.
Define RELIEF in the Park Model?
In the aftermath of event, rescue efforts focus on saving people & preventing further damage.
Define REHABILITATION in the Park Model?
Once the immediate impacts are under control, people start to resolve longer-term problems (shelter, aid).
Define RECONSTRUCTION in the Park Model?
Involves rebuilding permanent houses, infrastructure.
Define the 4 phases in the hazard Management Cycle? M P R R
- Mitigation = minimise impacts in future, build defences.
- Preparedness = Planning how to respond in future, warning systems.
- Response = How people react in disaster situation, emergency services rescue people.
- Recovery = Getting affected area back to normal, repairing rebuilding houses, restoring services.
Define the Earth’s core?
- Centre of earth
- Inner core = solid ball containing Iron & Nickel.
- Outer core = semi-molten containing Iron & Nickel.
- 6000oC hot
Define the Earth’s mantle?
- Around core is mantle (Silicate rock).
- Nearest to core/ quite rigid.
- Asthenosphere above mantle (semi-molten).
- 1000-3500oC hot.
Define the layers of the Earth?
- Inner core
- Outer core
- Mantle
- Asthenosphere
- Crust
Define 2 types of Crust?
- Continental = Is thicker (30-70km thick) less dense.
- Oceanic = Is thinner (6-10km thick) more dense.
Define tectonic plates?
- Lithosphere divided into many slabs, which move in relation to each other.
- Plates meet at plate boundaries/margins.
Define 3 theories why tectonic plates move?
- Convectional currents
- Slab pull
- Ridge push (Gravitational sliding)
Define CONVECTIONAL CURRENTS as a theory why tectonic plates move?
- Parts of asthenosphere heat up from core, less dense, slowly rise, then cool down and slowly sink.
- Circular movements of semi-molten rock called convection currents.
- Create drag on base of tectonic plate, making them move.
Define SLAB PULL as a theory why tectonic plates move?
- At destructive plate margins, denser crust is forced under less dense crust.
- Sinking plate edge pulls rest of plate towards boundary.
Define RIDGE PUSH as a theory why tectonic plates move?
- Constructive plate margin, magma rises to surface forms new crust.
- Surrounding rock heats, expands, rises above surface forming slope.
- New crust cools down, dense, gravity shifts denser rocks downslope, away from plate margin.
- Puts pressure on tectonic plate, causing then to move apart.
Define sea-floor spreading?
- As tectonic plates diverge, magma rises to fill gap.
- Sea bed gets wider as plates diverge, more magma fills gap.
- Creates mid-ocean ridges.
Define constructive margin?
Occurs where two plates move APART from eachother.
Define destructive margin?
Occurs where two plates are moving TOWARDS EACHOTHER (converging).
Define how a constructive plate margin causes volcanoes to erupt?
- Magma is less dense than the plate above, it rises and can erupt to form a volcano.
Define how a constructive plate margin causes earthquakes to happen?
- Plates don’t move apart in uniform.
- Causes pressure build-up, plates crack, making fault line causing earthquake.
Define 2 landforms created at a constructive margin?
- Ocean ridge
- Rift valley
Define OCEAN RIDGE as a constructive margin landform?
- Diverging plates underwater
- Underwater volcanoes erupt & build up above sea level.
- Mid-Atlantic Ridge (Eurasian & North American plate)
- Iceland built from underwater volcanoes build-up.
Define RIFT VALLEY as a constructive margin landform?
- Plates diverge beneath land, rising magma makes crust bulge & fracture, forming fault lines.
- Crusts between parallel fault lines drops down forming rift valley.
- East African Rift System (Mozambique –> Red Sea)
- Volcanoes found near rift valleys (Mount Kilimanjaro).
Define the landforms created at an OCEANIC-CONTINENTAL destructive margin? D F V E
- Deep-sea trench
- Fold mountains
- Volcanoes
- Earthquakes
Define how DEEP SEA TRENCH are formed at an OCEANIC-CONTINENTAL destructive margin?
- More dense oceanic crust is forced under less dense continental crust.
Define how FOLD MOUNTAINS are formed at an OCEANIC-CONTINENTAL destructive margin?
- Where plates meet.
- Made up of sediment that has accumulated on the continental crust, which are folded upwards along with the edge of the continental crust.
Define how VOLCANOES are formed at an OCEANIC-CONTINENTAL destructive margin?
- Magma less dense than continental crust and will rise back to surface forming a volcano.
Define how EARTHQUAKES are formed at an OCEANIC-CONTINENTAL destructive margin?
- One plate moves under other they get stuck.
- Causes pressure building up.
- Pressure breaks, plates jerk past each other, causing earthquake.
Define the landforms created at an OCEANIC-OCEANIC destructive margin?
- Denser plate submerged forming DEEP SEA TRENCH, triggering EARTHQUAKES & VOLCANIC ERUPTIONS.
- Volcanic eruptions that occur underwater form ISLAND ARCS.
Define the landforms created at a CONTINENTAL-CONTINENTAL destructive margin?
- Plates move towards eachother building pressure causing EARTHQUAKES.
- FOLD MOUNTAINS form when continental crusts converge.
Define conservative plate margins?
Occurs when two plates slide past eachother parallel.
Define EARTHQUAKES at conservative plate margins?
- Two plates get stuck alongside eachother, pressure builds, plates jerk forming fault lines causing an EARTHQUAKE.
- e.g. San Andreas Fault (California)
Define how magma plumes are formed at plate margins?
- Magma plume is a vertical column of extra-hot magma which rises up from mantle.
- Magma plume stationary over time, but crust moves above it.
- New volcanoes form above magma plume.
As crust moves, a row of volcanoes form on the land. - Hawaii is a magma plume.
Define where most volcanic eruptions take place?
Near constructive/destructive plate margins.
Define what the lava is like at a constructive plate margin?
- Basaltic lava formed here (very hot, low viscosity).
- Flows quickly
- Eruptions of basaltic lava are frequent, last long time.
- Not violent.
Define what the lava is like at a destructive plate margin?
- Andesitic & Rhyolitic lava formed here.
- Cooler, more viscous (Flows slower).
- Usually erupt intermittently, last short time.
- Subduction zones, melting plate forms magma, which rises to surface as volcano.
Define the 6 forms volcanic hazards can come in? P L V P M A
- Pyroclastic flows (nuée ardente)
- Lava flows
- Volcanic gases
- Pyroclastic & ash fallout
- Mudflows (Lahars)
- Acid rain