Tectonic processes and hazards Flashcards
What is the 3 structures of the earth
The crust
The mantle
The inner and outer core
The crust
Varies in thickness (5-10 km beneath the ocean).
1% of Earths total mass.
Made up of several major plates
The mantle
Widest layer (2900km thick) Heat and pressure makes rock liquid state
The inner and outer core
Hottest section (5000 degrees)
Mostly made of iron and nickel and is 4x denser than the crust.
Inner layer solid, outer layer liquid
What is a tectonic plate
A massive, irregularly shaped slab of solid rock, composed of both continental and oceanic lithospheres. Tectonic plates move in various ways against each other (plate margins)
What is slab pull
When older, denser tectonic played dunk into the mantle at subduction zones
What is ridge push
Gravitational force that causes a plate to move away from the crest of an ocean ridge, and into a subduction zone
Earthquake secondary effects
Liquefaction
Landslides and avalanches
Tsunamis
What is liquefaction
Solid material changed into a liquid state. Damage to building foundations, results in them sinking
How can earthquakes cause landslides and avalanches
Earthquakes in mountainous regions often cause landslides and avalanches. Steep, unstable slopes are notoriously unstable and vulnerable to landslides
How can earthquakes create tsunamis
Earthquakes occurring underwater can cause the seabed to rise, leading to the displacement of water, producing powerful waves which spread out from the epicentre
What is the epicentre of an earthquake
Point on the earths surface vertically above the focus in the crust where the earthquake begins
What is lahar
Volcanic mudflow which usually runs down a valley side on the volcano
What is pyroclastic flow
Fast moving current of super heated gas and ash (1000°C) Travels at 450 mph
What is an ash cloud
Small pieces of pulverised rock and glass which are thrown into the atmosphere
What was the magnitude of the Haiti earthquake
7.0
Where was the Haiti earthquake
15 miles of capital Port au Prince
Short term effects of Haiti earthquake
230,000 people died and 3 million effected
250,000 homes and 30,000 collapsed or damaged
Rubble blocked roads and ports
Long term effects of Haiti earthquakes
- 1 in 5 jobs lost
- Millions homeless
- Disease spread became big due to sanitation damage and corpse unburied
Immediate management of Haiti earthquake
- People tried to recover buildings and people
- Many countries responded with appeal and rescue teams
Long term management of Haiti earthquake
- International aid e.g $330 million from EU
- 6 months after, 98% rubble still remained
What is the richter scale
Measures earthquakes magnitude
How can you predict an earthquake
Scientists can reuse where earthquakes happen but not when
Examples:
Satellite surveying (tracks changes in earths surface)
Water table level (water levels fluctuate before an earthquake)
Radon gas sensor (Radon gas is released when plates move so this finds that)
How can you prepare for an earthquake
Training for emergency services
Practising earthquake drills
Emergency kits that include first aid items, blankets and tin food
How can you protect from earthquake
Building aseismic buildings
Raising public awareness
Improving earthquake prediction
How to predict a tsunami
No way of predicting ‘tsunami-causing earthquake’
Early warning systems can get word out of approaching tsunami
How to prepare for a tsunami
Evacuation routes on coastlines indicated by signs and signalled by sirens
DART ( Deep-ocean assessment and reporting of Tsunami) sea floor sensors can monitor passing tsunamis
How to protect from tsunami
Building designed with raised, open foundations and made of strong materials such as concrete
Tsunami walls have been built around settlements to protect them
How to predict volcanic eruptions
Seismometers to detect earthquakes
Thermal imaging can be used to detect heat around volcano
Gas samples may be taken and chemical sensors used to measure sulphur levels
Preparation for volcanic eruption
Exclusion zone around volcano
Emergency kit of key supplies
Evacuation routes
Trained emergency service ms with good communication systems
How are Divergent/Constructive Plate Boundaries formed
Caused by geologically recent mantle plume splitting a continental plate to create a new ocean basin. It can cause Basaltic volcanoes and minor earthquakes.
How is a Conservative Plate Boundary formed
Two plates slide past each other in either different directions or the same direction but at different speeds. As they shear past they can cause powerful earthquakes.
Formula for risk
Risk = hazard x exposure x vulnerability/manageability
When was the haiti earthquake
12 January 2010
Why is Unpredictability a risk
many hazards are not predictable and people can be caught out by timing or magnitude.
What is Dynamic Hazards
the threat from hazards fluctuates and human influence
can play a role.
What is cost-benefit
the benefit of staying in a hazardous location may outweigh the risk (perception of risk plays a role
here)
What is russian roulette reaction
the acceptance of the risk as something that will happen whatever you do, that is, one of fatalism.
What does deggs model show
shows that a natural disaster only occurs if a vulnerable population is exposed to a hazard.
