2.1 - EQs and Volcanoes Flashcards
Name the 2 types of volcano:
-shield
-strato (ie composite)
Describe and give an example of a shield volcano:
Mauna Kea
-very wide
-made of layers of basalt (cooled lava) with no ash layers
-thin lava (low viscosity)
Describe and give an example of a strato/composite volcano:
Mt Sinabung/Eyjafjallajökull
-very steep
-made of alternating basalt (cooled lava) and ash layers
-thicker layers than other volcanoes
-thick lava (high viscosity)
Describe the states a volcano can be in:
active - recent activity
dormant - no signs of activity but erupted in past 10,000 years
extinct - no chance of eruptions in future
Draw the internal structure of a general volcano:
draw
How are volcanic eruptions measured?
VEI, Volcanic Explosivity Index (log, goes from 1 to 8)
-factors in the amount of material ejected and how far it was dispersed
Define focus and epicentre:
-focus is exactly where the EQ originated from
-epicentre is the place on the ground directly above the focus
How are EQs measured?
Richter scale (log)
-measured by a seismometer
What is a tectonic plate?
-rock formed from lithosphere
-sits on top of the asthenosphere
-moved by convection currents in mantle
Describe the 2 types of tectonic plates:
continental (never subducts) - granite, thick but less dense
oceanic (subducts continental/less dense oceanic) - basalt, thin but more dense
Name the layers (and their properties) of the Earth:
-inner core (solid)
-outer core (liquid)
-mantle (plastic solid)
-asthenosphere (plastic solid)
-lithosphere (solid)
Describe and give an example of a constructive/divergent margin:
-plates move away
-volcanoes + small EQs
-N. America + Eurasian
Describe and give an example of a destructive/convergent margin:
-plates move towards
-volcanoes + largest EQs
-Nazca + S. American
Describe and give an example of a conservative/transform margin:
-plates move alongside (in different/same directions/speeds)
-EQs ONLY
-Pacific + N. American (San Andreas Fault)
What is a collision zone?
-2 continental plates at a destructive/convergent margin
-both are uplifted, no subduction
Explain how a volcano/fold mountain can form at a destructive/convergent margin:
-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
Why do EQs have more devastating effects in LEDCs?
-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
How might the impacts of volcanoes/EQs be reduced?
(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
Why might an eruption not cause many deaths, even though lots of people live nearby?
-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)
How are fold mountains formed?
-convergent/destructive margin (mention convection currents)
-mention subduction if applicable
-other/both plates are uplifted
Define an earthquake:
the shaking of the ground caused by sudden movement of the Earth’s crust
Give some direct and indirect hazards faced by those who live in areas affected by volcanoes:
-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
How would you describe the distribution of EQs in this image?
-in lines
-mostly along plate margins
-a few in the middle of plates
-lots along Pacific Ring of Fire
Explain why it is necessary to provide clean water and sanitation after an EQ:
-no place to clean themselves
-disease could spread (cholera) due to damaged sewage systems
-could develop into a larger pandemic
