Volcanos And Earthquakes Flashcards
Why are there different types of volcanoes?
Lava is formed when magma erupts to the earths surface as lava
The type of lava can effect the formation of the volcano
What are strato volcanoes?
At a destructive plate boundary -> subduction zone
Alternating layers of ash and lava
Lava: acidic, viscous, slow flow
Eruptions: violent, exploding, pressure builds up, high VEI (volcanic explosivity index)
Rare
Steep sides
What are shield volcanoes?
Constructive plate boundary or hot spots
Layers of cooled runny lava
Lava: basic, fluid, fast flow, runny
Eruption: gentle, quite, gases escape, low VEI
Frequent
Gently sloping sides
What are three types of volcanoes (regarding activity)?
Active:
Recently erupted and is likely going to erupt again (Mt. Etna)
Dormant:
Erupted in the last 2000 years and could possibly erupt again (Mt. Pinatubo)
Extinct:
No evidence of eruption in historic times and no evidence of a magma reservoir (Edinburgh)
What are the features of a volcanic eruption?
Lava:
Magma on surface -> lava
Viscosity depends on the composition of the magma
Ash:
Pulverized solid lava with less than 2mm diameter
Ejected into atmosphere -> travel far
Pyroclastic flow:
Fast and hot clouds of poisonous gas with ash
Around 100-700 km/h
Lahars:
Snow and ice melts and combines with ash
Fast mudflows or lahars
Volcanic bombs:
Fragments of molten rock ejected from volcano
60mm-5m in diameter
Name the features of a volcano, and draw a diagram + label
Magma:
Molten rock
Lava:
Magma once it reaches the surface
Magma chamber:
Chamber full of magma
Main vent:
The main path that magma follows (usually in the middle)
Pressure from within the earth pushes magma
Crater:
Main opening
Secondary cone:
A smaller tube that magma can escape from if the main vent is blocked
Ash cloud and volcanic bombs:
Cloud and rocks
Dyke and sill:
When magma is forced through layers and cooled before reaching the surface
Dyke: vertical
Sill: horizontal
What are earthquakes?
Shockwaves/energy travelling through the earth that travels in all directions from a focal point
What are the features of an earthquake?
Focus:
The point the earthquake started below the surface
epicenter:
Point on the earth surface directly above focus
Magnitude:
Amount of energy released by the earthquake
How is magnitude measured?
Richter:
Energy released
Open ended scale
Logarithmic
On earth-> no more than 10
Moment:
More accurate for larger
Quantitative measure of magnitude (relative size)
Seismic moment rather than amplitudes of waves
Mercalli:
Damages caused
1-12
Arithmetic
What are the sequences of an earthquake?
Tectonic plate moves and get stuck
Pressure build and plates try to move
The plates free, but the pressure is released as energy
Earthquakes starts and focus
Epicenter -> directly above the focus
Energy passed through the crust in waves
What parts of the world experience the most earthquakes?
Along the boundaries of the plates (narrow belts)
90% around pacific ring of fire
What are the layers of the earth?
Crust:
Solid and broken up into plates
Continental -> thicker (23-90km), older, lighter, can’t sink, permanent
Oceanic -> thinner (5-10km), heavier, can sink
->Constantly being renewed (subduction and sea floor spreading, plate movement)
Mantle:
Semiliquid
Convection current -> moves mantle -> moves crust (plates)
Outer core: Liquid metal
Inner core solid metal (pressure)
Earth: 12800 km wide
What are tectonic plates?
Sections of the crust which are moved by the movement of he mantle
Boundary/margin -> where 2 plates meet
What are the 4 types of boundaries?
Constructive, destructive, collision and conservative
What are constructive (divergent) boundries?
Plates move apart, and magma rises from the mantle -> new crust (sea floor spreading)
Ex: mid Atlantic ridge
Both volcanic eruptions and earthquakes (esp shield) can happen
What are destructive (convergent) plate boundries?
Plates move together
Oceanic + continental -> denser oceanic plate sinks (subduction)
-> subduction zone (trenches)
Ex: Nazca plate (down) and South American plate (up)
Both volcanic eruption (oceanic crust melts and makes magma which rises) and earthquakes (pressure created as plate forced down)
Mainly:
Strato volcano
Fold mountains
Island arcs (many volcanos in succession)
Tsunamis (due to eruption of shallow earthquakes)
What are collision plate boundaries?
2 plates of similar density (continental) move towards each other
Land pushed up -> mountains
Mainly earthquake hazard
What are conservative plate boundaries?
Plates slide past each other -> opposite directions or same direction different speed
No landform or volcanos
Can cause earthquakes
Ex: pacific and NA plates
Slide -> stick -> pressure -> shockwaves
Where are volcanos likely to occur?
Along constructive and destructive boundaries
Active volcanos (75%) are near ring of fire
Hotspots -> at plate boundaries -> columns of magma which escape
What are effects of earthquakes?
Primary:
Ground shakes
Surface ruptures
Secondary:
Liquefaction (shaking)
Landslides
Tsunamis
Fires
After shocks
What are effects of earthquakes? (Pt.2)
Overall:
Loss of life + injury
Building collapse
Destruction of transport
Loss of jobs and businesses
Loss of crops
Damaged environment
What factors can effect the impact of an earthquake?
Building construction and design
Building density (domino effect)
Population density
Preparation and planning
Economic wealth
Time of day
Magnitude (geology, distance from epicenter, focus depth)
How are volcanos formed at hotspots?
As the plate moves, the hotspot (plume of magma) gets through the crack of the plate, and as the plate moves there is a trail of islands left behind
What are effects of volcanoes?
Primary:
Pyroclastic flow
Lava flow
Volcanic bombs
Lamar
Earthquakes
Ash fall
Vegetation destroyed
Secondary:
Land slides
Tsunamis
Acid rain
Ash fallout
Damaged roads and infrastructure
Unemployment
What are effects of volcanoes (pt.2)?
Loss of life + injury
Destruction of buildings
Destruction of transport network
Loos fo job and businesses
Loss of crop
Power and water supply damaged
What can effect the impact of a volcanic eruption?
Proximity
Planning and prep (evacuation plans)
Magnitude
Type of volcano
Amount of ash ejected
What are some advantages of living near a volcano prone area?
Fertile soil -> lava has minerals which make good soil
Tourism -> danger tourism and provides jobs
Minerals and precious stones -> mined and sold
Geothermal energy -> generate energy
New land area -> islands and such
Other reasons:
Don’t have another option
Nowhere to go
Work, education, income
Emotional support (friends and family)
Confidence in prep and precautions
Unaware of risk
Benefit outweighs risk
Aren’t very frequent
What can be done to reduce the impact of an earthquake?
Short term:
Aid
Disaster relief
Emergency shelter and food
Long term:
Monitoring and guessing earthquakes (study earth, migration, patterns, radon gas emissions)
Good engineering (flexible building materials, steel beams, rubber shock absorbers, shatterproof glass, friction dampers) earthquake drills
Education
Training emergency services
Warning system
What can be done to reduce the impact of volcanoes?
Short term:
Aid disaster relief
Emergency food and shelter
Long term:
Prediction (tremors increase, ground temp rises, increase amount of gas and steam emitted)
-> satellites about ground movement
->GIS (geographical information system) (vulnerable areas, land use, infrastructure)
-> land use planning (GIS used)
Mapping areas at risk
Planning (services prepared)
Dense housing -> away from high risk areas
Preparation:
Monitoring and warning systems
Evacuation plan (food, shelter, transport)
Training emergency servies
Organizing plans and servies
Education
