2.1 - EQs and Volcanoes

Question 1

Name the 2 types of volcano:

Answer 1

-shield
-strato (ie composite)

Question 2

Describe and give an example of a shield volcano:

Answer 2

Mauna Kea

-very wide
-made of layers of basalt (cooled lava) with no ash layers
-thin lava (low viscosity)

Question 3

Describe and give an example of a strato/composite volcano:

Answer 3

Mt Sinabung/Eyjafjallajökull

-very steep
-made of alternating basalt (cooled lava) and ash layers
-thicker layers than other volcanoes
-thick lava (high viscosity)

Question 4

Describe the states a volcano can be in:

Answer 4

active - recent activity

dormant - no signs of activity but erupted in past 10,000 years

extinct - no chance of eruptions in future

Question 5

Draw the internal structure of a general volcano:

Answer 5

draw

Question 6

How are volcanic eruptions measured?

Answer 6

VEI, Volcanic Explosivity Index (log, goes from 1 to 8)

-factors in the amount of material ejected and how far it was dispersed

Question 7

Define focus and epicentre:

Answer 7

-focus is exactly where the EQ originated from

-epicentre is the place on the ground directly above the focus

Question 8

How are EQs measured?

Answer 8

Richter scale (log)

-measured by a seismometer

Question 9

What is a tectonic plate?

Answer 9

-rock formed from lithosphere
-sits on top of the asthenosphere
-moved by convection currents in mantle

Question 10

Describe the 2 types of tectonic plates:

Answer 10

continental (never subducts) - granite, thick but less dense

oceanic (subducts continental/less dense oceanic) - basalt, thin but more dense

Question 11

Name the layers (and their properties) of the Earth:

Answer 11

-inner core (solid)
-outer core (liquid)
-mantle (plastic solid)
-asthenosphere (plastic solid)
-lithosphere (solid)

Question 12

Describe and give an example of a constructive/divergent margin:

Answer 12

-plates move away
-volcanoes + small EQs

-N. America + Eurasian

Question 13

Describe and give an example of a destructive/convergent margin:

Answer 13

-plates move towards
-volcanoes + largest EQs

-Nazca + S. American

Question 14

Describe and give an example of a conservative/transform margin:

Answer 14

-plates move alongside (in different/same directions/speeds)
-EQs ONLY

-Pacific + N. American (San Andreas Fault)

Question 15

What is a collision zone?

Answer 15

-2 continental plates at a destructive/convergent margin
-both are uplifted, no subduction

Question 16

Explain how a volcano/fold mountain can form at a destructive/convergent margin:

Answer 16

-convection currents in mantle carry plates together, and oceanic subducts at the oceanic trench

-water dragged into subduction zone causes some of the asthenosphere directly above it to melt into liquid magma

-less dense magma rises up through asthenosphere, accumulating in the continental plate, eventually piercing through to form a volcano
-collision can also result in fold mountains

visual explanation from 1:03 by Kurzgesagt

Question 17

Why do EQs have more devastating effects in LEDCs?

Answer 17

-poor infrastructure
-high population densities so more affected
-poor medical/emergency services (which also collapse) so no treatment
-lack of education/evacuation procedures
-lack of money for rebuilding and training of emergency services

Question 18

How might the impacts of volcanoes/EQs be reduced?

Answer 18

(both)
-monitoring activity
-educating public on evacuation procedures

(EQs)
-tsunami walls + warning alarms
-EQ proof buildings + strict regulations (eg reinforced/shatterproof glass)
-don’t build many high rise buildings

Question 19

Why might an eruption not cause many deaths, even though lots of people live nearby?

Answer 19

-signs of eruption before it erupts (eg smoke coming out of crater)
-eruptions can be predicted so people can be warned
-lava often moves slowly and only affects a limited area
-lava diversion channels are built
-education on how to stay safe in an eruption (eg planned evacuation routes)

Question 20

How are fold mountains formed?

Answer 20

-convergent/destructive margin (mention convection currents)
-mention subduction if applicable
-other/both plates are uplifted

Question 21

Define an earthquake:

Answer 21

the shaking of the ground caused by sudden movement of the Earth’s crust

Question 22

Give some direct and indirect hazards faced by those who live in areas affected by volcanoes:

Answer 22

-lava/ash/pyroclastic flow
-poisonous fumes
-volcanic bombs
-mudflow

-death/injury from collapsed buildings/fire
-damage to roads/possessions (eg cars)
-loss of water/electricity/gas supply

Question 23

How would you describe the distribution of EQs in this image?

Answer 23

-in lines
-mostly along plate margins
-a few in the middle of plates
-lots along Pacific Ring of Fire

Question 24

Explain why it is necessary to provide clean water and sanitation after an EQ:

Answer 24

-no place to clean themselves
-disease could spread (cholera) due to damaged sewage systems
-could develop into a larger pandemic