Earthquakes and Volcanoes Flashcards
How are earthquakes made?
When friction between moving plates work against convection currents to build up stress, and when the plates can’t take it anymore, they release a powerful wave of energy.
Where do earthquakes occur? Where do most earthquakes occur?
Anywhere on Earth.
Earthquakes often occur at tectonic plate boundaries.
Define focus.
The location inside Earth where an earthquakes starts.
What begins at the focus?
Energy release of an earthquake.
Define epicentre.
The point on Earth’s surface directly above the focus.
How do scientists classify earthquakes?
By the depth of the foci (plural for focus)
How deep is a shallow focus?
1 to 70 km
How deep is a intermediate focus?
70 to 300 km
How deep is a deep focus?
300km +
The amount of surface damage an earthquake can cause depends on its ________.
depth
Do shallow-focus earthquakes cause more damage or deep-focus earthquakes?
Shallow-focus earthquakes
Define seismology
The study of earthquakes and seismic waves.
Define seismic waves.
Vibrations from energy released by an earthquake.
What can P-waves travel through?
Everything
What affects the movement of body waves?
The composition and depth of the different layers of Earth.
What are seismometers (seismographs)?
Devices that measure the amount of ground motion caused by an earthquake.
What is a seismogram?
A record of ground motion produced by a seismometer.
Define magnitude.
A number that rates the strength of an earthquake.
Ratio of magnitude and size of seismic waves.
1-step increase on magnitude scale = 10 times larger seismic waves
What can seismograms show scientists?
- Time of the earthquake
- How long it lasted
- Amount of ground shaking
- How fast seismic waves are travelling
What are the three distinctive types of volcanoes?
`composite volcanoes
- shield volcanoes
- rift eruptions
What is a composite volcano?
A large, cone-shaped, belching ash, rocks, and lava volcano. Basically the typical one.
Why are composite volcanoes cone-shaped?
It’s because of repeated eruptions of ash and lava, wich builds up layers. (or strata)
Describe the process of eruption.
As the magma approaches the surface, gas gets trapped below, and pressure builds up. Once the pressure is too great to be contained, there is an explosive eruption.
Where are composite volcanoes usually found?
Near subduction zones
What are the largest type of volcanoes?
Shield volcanoes.
Where do shield volcanoes form?
Over hot spots.
Where does a hot spot occur?
It occurs where a weak part of the lithosphere allows magma to break through.
Where do shield volcanoes typically occur?
In ocean basins.
Define supervolcano.
A term used to describe past volcanoes with massive eruptions that not only destroy nearby areas, but also affected life around the planet.
Where do rift eruptions occur?
Through long cracks in the lithosphere.
What are the characteristics of rift eruptions?
- not very explosive or violent
- curtain-like eruptions
- Releases enormous amounts of lava.
