Tectonic Hazards Flashcards
3 main sections of the earth
crust
mantle
core
Describe the structure of the crust
10-70km thick
less than 1% of earth’s volume
made from rocks like granite and basalt
range up to 800 degrees celsius
Name 2 types of plates
Continental and Oceanic
Give the characteristics of the mantle
thickness of 2900km
800 to 3000 degrees celsius
Give the characteristics of the core
inner and outer core
contain iron and nickel mainly
range from 3000 to 5000 degrees celsius
2 causes that make tectonic plates move
convection currents
slab pull force
Plates that move away are…
divergent plates
Plates that move towards each other are…
convergent plates
What is a plate boundary?
Point where two or more plates meet
Divergent plate boundary typically form…
Rift alleys & block mountains
Ridges
Volcanoes
Convergent plates often form…
trenches
fold mountains
volcanoes
Transform plates often form…
earthquakes.
Define what a volcano is
landform formed by magma ejected from the mantle onto earth’s surface
How do earthquakes occur?
2 plates slide past each other horizontally, build up tension & pressure which results in violent earthquakes when released
Examples of continental continental plate divergence.
Between African plate Nubian and Arabian plate
Describe continental continental plate divergence
two plates forced apart from each other due to rising and diverging mantle convection currents
plates stretch and cause fractures
Landforms of continental continental plate divergence
rift valley
earthquake
block mountains
When plates diverge and fracture the crust it is also known as…
Faulting
Landforms of oceanic oceanic plate divergence
mid oceanic ridge
volcanoes
When lava cools and solidifies after flowing out onto the sea floor it is known as…
Sea floor spreading
What is rift valley?
Rift valley: valley with steep sides
What is mid oceanic ridge?
Central ridge structure that divides ocean base in half
What is block mountain?
Block mountain: block of land with steep slopes left standing higher than surrounding land
Landforms of oceanic oceanic plate convergence
Island volcano
trench
Describe oceanic oceanic convergence
2 plates converge, denser one subduct under less dense. area where denser plate subducts underneath is subduction zone.
What is subduction zone?
region where 1 plate is forced down into mantle beneath 2nd plate
Describe oceanic continental plate convergence
denser oceanic plate subducts under less dense continental plate, subduction zone occurs and continental plate lifted up
Why can’t 2 continental plates subduct?
both are too thick and buoyant, causing collision, this cause them to break and slide along fractures in crust instead
What is folding?
when pressure from resultant compressional force causes the layers of rock to buckle and fold upwards/sideways to create fold mountains
Upfold and downfold of a fold mountain is known as…
Anticline and syncline respectively
Characteristic of low silica lava
viscosity & gases and explosiveness
Low viscosity, flow more easily.
Gases can escape easily thus eruptions are less explosive
Characteristic of High silica lava
Viscosity & gases
Higher viscosity, trap gases more easily, cause pressure to build up and has a larger outward explosion
How is a stratovolcano formed?
formed by successive eruptions of high-silica lava & pyroclasts
Where are shield volcanoes mostly located?
divergent plate boundaries
Where are shield volcanoes mostly located?
divergent plate boundaries
Shape of stratovolcano
High, slight concave shape, steeper at top & gentler at base
Shape of stratovolcano
High, slight concave shape, steeper at top & gentler at base
Shape of shield volcano
Gently sloping sides
broad summit
Shape of shield volcano
Gently sloping sides
broad summit
What kind of destruction can volcanic materials cause?
When eruption occurs, lava & pyroclasts released contains ash rock and volcanic bombs
lava contain high temp 500-1400
pyroclastic flow can go faster than 80km/h
What kind of destruction can volcanic materials cause?
When eruption occurs, lava & pyroclasts released contains ash rock and volcanic bombs
lava contain high temp 500-1400
pyroclastic flow can go faster than 80km/h
How can pollution affect people living near volcanoes?
ash can block sunlight, suffocate crops & trigger sever respiratory problems
4 benefits of living near volcanic areas
- Fertile soil
- Precious stones and minerals
- Tourism
- Geothermal energy
How is fertile soil formed from eruptions?
Lava & ash break down from eruptions to form fetile volcanic soils that are rich in minerals.
How are precious stones and minerals created from volcanic eruptions?
The magma that rises from earth contains a range of precious stones & minerals that can be extracted after upper layers of volcanic rocks have been eroded
Why do volcanic areas help tourism?
Volcanic areas attract millions of tourists due to many activities, and their rich history
E.G. POMPEII, 3000000 tourists visit a year
Why do volcanic areas help tourism?
Volcanic areas attract millions of tourists due to many activities, and their rich history
E.G. POMPEII, 3000000 tourists visit a year
How is geothermal energy created from eruptions?
Groundwater is heated up by hot rocks beneath surface as steam, drives turbines to produce electricity
E.G. almost 2/3 of iceland electricity supply is from geothermal energy
What is epicentre?
Point on earth’s surface directly above focus
6 factors that affect *impact * of earthquake
- Magnitude of earthquake
- Population density
- Level of preparedness
- Distance from epicentre
- Time of occurence
- Type of soil
What is liquefaction ?
When ground becomes unstable & saturated soil flows like liquid
Hazards associated with earthquake zones
- tsunamis
- disruption of services
- destruction of property & infrastructure
- Landslides
- Loss of lives
State preparedness measures to tackle earthquakes
theres 4
- Land use regulations
- Infrastructure
- Emergency drills
- Earthquake monitoring system
Strength & weakness of Land use regulation
Strength: enforced along coasts to ensure protective barriers to protect buildings from tsunamis
Weakness: not easy to implement in existing built-up areas/ privately owned land, thus costly
Strength & weakness of Infrastructure
Strength: withstand vibration by earthquakes without shaking easily
Weakness: Costly [very]
Strength & weakness of Emergency drills
Strength: raise people awareness and reduce panic and irrational behaviour when earthquakes occur
Weakness: not effective when insufficient time for evacuation
Strength & weakness of Earthquake monitoring system
Strength: can estimate magnitude and frequency at fault lines
Weakness: costly, inaccurate, interfered easily, only provides general indication
2 short term responses
Search & rescue
Emergency, food & medical supplies
Elaborate on strengths & weaknesses of search & rescue
locate & free trapped people
s: can save survivors who were trapped without food
w: rescue workers only have 72 hours
Elaborate on strengths & weaknesses of emergency, food & medical supplies
provide immediate medical help
s: civilians carry on lives easily after disaster
w: insufficient supplies lead to social unrest
