Volcanos And Earthquakes

Question 1

Why are there different types of volcanoes?

Answer 1

Lava is formed when magma erupts to the earths surface as lava
The type of lava can effect the formation of the volcano

Question 2

What are strato volcanoes?

Answer 2

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

Question 3

What are shield volcanoes?

Answer 3

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

Question 4

What are three types of volcanoes (regarding activity)?

Answer 4

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)

Question 5

What are the features of a volcanic eruption?

Answer 5

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

Question 6

Name the features of a volcano, and draw a diagram + label

Answer 6

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

Question 7

What are earthquakes?

Answer 7

Shockwaves/energy travelling through the earth that travels in all directions from a focal point

Question 8

What are the features of an earthquake?

Answer 8

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

Question 9

How is magnitude measured?

Answer 9

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

Question 10

What are the sequences of an earthquake?

Answer 10

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

Question 11

What parts of the world experience the most earthquakes?

Answer 11

Along the boundaries of the plates (narrow belts)
90% around pacific ring of fire

Question 12

What are the layers of the earth?

Answer 12

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

Question 13

What are tectonic plates?

Answer 13

Sections of the crust which are moved by the movement of he mantle
Boundary/margin -> where 2 plates meet

Question 14

What are the 4 types of boundaries?

Answer 14

Constructive, destructive, collision and conservative

Question 15

What are constructive (divergent) boundries?

Answer 15

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

Question 16

What are destructive (convergent) plate boundries?

Answer 16

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)

Question 17

What are collision plate boundaries?

Answer 17

2 plates of similar density (continental) move towards each other
Land pushed up -> mountains
Mainly earthquake hazard

Question 18

What are conservative plate boundaries?

Answer 18

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

Question 19

Where are volcanos likely to occur?

Answer 19

Along constructive and destructive boundaries
Active volcanos (75%) are near ring of fire
Hotspots -> at plate boundaries -> columns of magma which escape

Question 20

What are effects of earthquakes?

Answer 20

Primary:
Ground shakes
Surface ruptures

Secondary:
Liquefaction (shaking)
Landslides
Tsunamis
Fires
After shocks

Question 21

What are effects of earthquakes? (Pt.2)

Answer 21

Overall:
Loss of life + injury
Building collapse
Destruction of transport
Loss of jobs and businesses
Loss of crops
Damaged environment

Question 22

What factors can effect the impact of an earthquake?

Answer 22

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)

Question 23

How are volcanos formed at hotspots?

Answer 23

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

Question 24

What are effects of volcanoes?

Answer 24

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

Question 25

What are effects of volcanoes (pt.2)?

Answer 25

Loss of life + injury
Destruction of buildings
Destruction of transport network
Loos fo job and businesses
Loss of crop
Power and water supply damaged

Question 26

What can effect the impact of a volcanic eruption?

Answer 26

Proximity
Planning and prep (evacuation plans)
Magnitude
Type of volcano
Amount of ash ejected

Question 27

What are some advantages of living near a volcano prone area?

Answer 27

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

Question 28

What can be done to reduce the impact of an earthquake?

Answer 28

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

Question 29

What can be done to reduce the impact of volcanoes?

Answer 29

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