1.3 Physical processes causing hazards Flashcards
1
Q
what is a hypocentre?
A
the point at which the earthquake actually happens
2
Q
what is the epicentre?
A
directly above the hypocentre (on the Earths surface)
3
Q
what are seismic waves?
A
- waves that transmit the energy released by an earthquake
- 3 types- P, S, L
4
Q
what is a fault?
A
- a fracture in the rocks that make up the earths crust
5
Q
what are primary or p waves?
A
- vibrations caused by compression
- travel fastest
6
Q
what are secondary or s waves?
A
- slower, vibrate at right angles to direction of travel, cannot pass through water
- up and down
7
Q
what are long or l waves?
A
- surface waves, vibration in horizontal plain- high amplitude
- side to side
8
Q
what are primary hazards?
A
- caused by the direct interaction of seismic wave energy with the ground- usually surface rupture or ground shaking
9
Q
what are secondary hazards?
A
- caused as a consequence of the ground shaking e.g. ground settlement, liquefaction and landslides
10
Q
what is soil liquefaction?
A
- shaking from the earthquake destabilises the soil by increasing the space between grains
- with its structure lost, the soil flows like a liquid
11
Q
what does the richter scale measure?
A
- measure the amount if energy released (magnitude)
- logarithmic scale e.g. a magnitude 5 is 10x more powerful than a 4
- biggest ever- 9.5, Chile 1960
12
Q
what does the mercalli scale measure?
A
- measures the effects of an earthquake
- scale 1-12 based on observations
13
Q
what are the three ways volcanoes are formed from?
A
- hotspot volcano
- constructive boundaries
- destructive boundaries
14
Q
what are the 4 types of volcanoes?
A
- lava dome
- shield
- composite
- cinder cone
15
Q
what measures volcanoes?
A
- the volcanic explosive index (VEI)
- 0-8, logarithmic scale
- dependent on- the amount snd height of material ejected, length of eruption
16
Q
what is a lava flow?
A
- streams of molten rock that pours or oozes from an erupting event
- a primary hazard
17
Q
what is a pyroclastic flow?
A
- a dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing at great speed.
- a primary hazard
18
Q
what is a tephra?
A
- also known as ash fall, tephra is a solid material of varying grain size ejected into the atmosphere
- a primary hazard
19
Q
what are volcanic gases?
A
- the fluid gas phase released by active volcanoes, composed of mainly water, carbon dioxide and sulphur dioxide
- a primary hazard
20
Q
what are lahars?
A
- a hot or cold mixture of water and rock fragments that flow quickly down the slopes of a volcano
- a secondary hazard
21
Q
what are jokulhlaups
A
- floods caused by the sudden release of water and rocks when glacial ice is melted by the volcanic eruption
- a secondary hazard
