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Tectonics Flashcards

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1
Q

What are primary seismic hazards?

A

earthquakes

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2
Q

What are secondary seismic hazards?

A

tsunamis, landslides, liquifaction

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3
Q

What are primary volcanic hazards?

A

volcanic eruption (lava flow, ash etc.)

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4
Q

What are secondary volcanic hazards?

A

lahar (boiling hot mud flow), jokellhaup (glacial burst)

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5
Q

What is the name for a glacial burst?

A

jokellhaup

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6
Q

What is a lahar?

A

a boiling hot mud flow

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7
Q

What three things make a plate move?

A

1- heat created by the core by radioactive decay
2- this creates convection currents in the mantle
3- crust is moved by Frictional drag where the plates come into contact with a convectional cell

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8
Q

What is slab pull, ridge push?

A

ridge pushes, weight of slab end pulls down

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9
Q

How does ridge push work?

A

the convectional currents push up the plates at the ridge and gravity causes them to slide apart

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10
Q

How does slab pull work?

A

the new crust being created at the ridge as the plates slide apart is much thinner than the bottom of the plate, so the bottom is heavier, causing it to slide more.

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11
Q

What else does slab pull, ridge push lead to?

A

it also causes subduction- gravity causes the plates to move faster at destructive plate boundaries as they slip under one another because the heaviest part of the plate subducts (like pulling a chain off a table)

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12
Q

What is another name for conservative plate boundaries?

A

transform boundaries

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13
Q

What is another name for constructive plate boundaries?

A

divergent boundaries

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14
Q

What is another name for destructive plate boundaries?

A

convergent boundaries

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15
Q

What happens at conservative/transform plate boundaries?

A

plates move past each other

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16
Q

Are there earthquakes at conservative plate boundaries?

A

yes- as the plates move past each other friction builds as they snag. When the stress energy is released, shock waves through the crust cause earthquakes

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17
Q

Are there eruptions at conservative plate boundaries?

A

no, because no crust is made or destroyed

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18
Q

What is an example of a conservative plate boundary?

A

the San Andreas Fault in California

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19
Q

What is happening at the San Andreas Fault in California?

A

The Pacific plate is moving NW at a faster rate than the North American plate.

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20
Q

What are the earthquakes usually like along conservative boundaries?

A

almost always very shallow in focus because of the lateral movement

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21
Q

What happens at constructive boundaries?

A

As the plates move apart they leave cracks and fissures that allows magma to escape from the highly pressurized interior of the planet. Magma fills the gaps and eventually erupts to the surface and cools as new land.

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22
Q

What type of lava is erupting under the sea?

A

Basaltic, so it can travel long distances and create gentle sloping features- this can result in huge ridges of undersea mountains and volcanoes

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23
Q

What is an example of an underwater constructive plate boundary?

A

the mid Atlantic Ridge

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24
Q

What happens at the mid Atlantic Ridge?

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A

the Eurasian Plate moves away from the North American plate a rate of around 4cm a year- this is how Iceland came to exist

25
What is an example of a constructive plate boundary on land?
the Great African Rift Valley in Eastern Africa
26
What is happening along the Great African Rift valley?
the Eastern section is moving North East while the Western section is moving West and North West- the crust is fracturing, so as it moves apart, sections drop downwards.
27
Which volcanoes are along the Great African Rift Valley?
Kilimanjaro in the East and Ruwenzori in the West
28
What happens at destructive plate boundaries?
a dense oceanic plate is pushed towards a less dense continental plate at a subduction zone creating a deep ocean trench
29
Where are destructive plate boundaries mainly found?
around oceans- mostly the Pacific Ring of Fire
30
At what angle do tectonic plates subduct?
it varies- beneath Peru is 10-15 degrees, while beneath Japan it is 40-45 degrees
31
What happens to a subducting plate as it descends?
it is melted by friction and increasing pressure and heat from the asthenosphere
32
What is the asthenosphere?
the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.
33
What are volcanoes caused by?
they are caused by molten material making its way up through fissures in the crust to collect in magma chambers, from which it eventually emerges- creating volcanic mountains or islands
34
Why are volcanoes explosive?
because magma from subduction is silica rich, gas laden, and under a lot of pressure
35
Do earthquakes occur along destructive plate boundaries?
yes- they are caused by the movement of the plates grinding past each other, when one plate slips past releasing seismic energy
36
Where do earthquakes occur along destructive plate boundaries?
they occur along the inclined zone of subduction in the Benioff Zone
37
Why do earthquakes occur in subducting tectonic plates?
shallow earthquakes in the descending slab are from fracturing in the outer part of the downward bending oceanic crust- in the continental crust they are caused by block uplift and subsidence
38
At what boundaries are fold mountains formed?
destructive/convergent plate boundaries
39
What is an example of fold mountains?
the Andes- the South American plate is being crumpled up above the subducting Nazca plate.
40
Where are the world's highest volcanoes?
in the fold mountains of the Andes
41
What is a major secondary hazard at destructive plate boundaries?
tsunamis
42
How are fold mountains formed?
at continental collisions at destructive plate boundaries, neither plate is denser, so fold mountains form
43
What is Moho Discontinuity?
where the mantle meets the crust- the crust is melting
44
What is an Upwelling?
when the magma comes up at plate boundaries at constructive margins (gentle- not very explosive- more gradual)
45
Can there be earthquakes at constructive plate boundaries?
yes- because the different part of the plates can move at different speeds, causing TRANSFORM FAULTS to appear at right angles to the boundaries, and act as mini conservative boundaries causing small earthquakes of magnitude 3 or 4
46
What is a Natural Hazard?
extreme natural events that have the potential to threaten life and property
47
What is a DISASTER?
a sudden, calamitous event that seriously disrupts the functioning of a community and causes human, material, and economic or environmental losses that exceed the community's ability to cope using its own resources
48
What is the RISK EQUATION?
Risk= (Hazards x Vulnerability) / Capacity
49
Explain the RISK EQUATION?
the risk of a disaster grows as global hazards and people's vulnerability increases, while their capacity to cope decreases
50
What is a community's threshold for resilience or capacity to cope?
a resilience to a natural hazard because some communities are better prepared
51
What is the Pressure and Release Model (PAR)?
helps us to understand the underlying causes of disaster that create vulnerability against the hazard event- the two most important causes of vulnerability are governments and economic status
52
What is Vulnerability?
the conditions determined by physical, social, economic, and environmental factors which increase to susceptibility of a community to the impact of national hazards
53
What is Degg's Model?
a venn diagram with Vulnerable Population in one bubble, Hazardous Event in the other, and Disaster in the intersection
54
What was the supercontinent called?
Pangaea
55
When was Pangaea around?
300 million years ago
56
When did Pangaea begin to break up?
200 million years ago
57
Who came up with the theory of continental drift and when?
Wegener in 1912- he stated that all the continents used to be stuck together
58
How did Wegener come up with the theory of continental drift?
he noticed that mountain ranges were formed when the edge of drifting continents crumpled and folded when they collided with other continents as was the case for Himalayas, forming when India collided with Asia
59
Who came up with the idea of Sea Floor Spreading and when?
Harry Hess in 1962

Physical Geography (5 decks)

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