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Tectonics > EQ1 > Flashcards

EQ1 Flashcards

1
Q

inner core

A

7000° C
very dense-13.5g/cm³
20% nickel
80%iron

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2
Q

outer core

A

4400-6100°C
dense-10 to 12 g/cm³
iron and nickel

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3
Q

mantle

A

870°C
less to medium density-3 to 5 g/cm³
phases of liquid and solid-partially molten

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4
Q

what is the mantle made of?

A

peridotite=igneous rock made of minerals olivine and pyroxine
higher-more olivine
lower-more magnesium silicate

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5
Q

what waves pass through the crust?

A

crust=solid

surface and body waves can pass through.

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6
Q

what waves pass through the mantle?

A

mantle=partially molten

body waves pass though at variable rates due to changes in density.

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7
Q

what waves pass through the outer core?

A

outer core=liquid (generates magnetic field)

only p waves can pass through, so an s wave ‘shadow zone’ is created.

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8
Q

what waves pass through the inner core?

A

only p waves reach the inner core and pass through but their refraction at the core mantle boundary creates a ring p wave ‘shadow zone’ between 105 and 140 degrees from the focal point.

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9
Q

what is the hypocentre?

A

‘focus’ point within the ground where seismic waves are first released.

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10
Q

what is the epicentre?

A

point on land directly above the hypocentre.

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11
Q

where are the active intra plate volcanoes?

A

1) east africa

2) hawaii

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12
Q

what is happening in the east african rift zone?

A

actively splitting African and Arabian plate meet at a triple junction, where the Red Sea meets the Gulf of Aden. When the crust stretches beyond its limits, tension cracks begin to appear on earth’s surface. Magma rises and squeezes through these widening cracks, sometimes erupting and forming volcanoes.

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13
Q

what is the Benioff zone ?

A

an area of seismicity corresponding with the slab being thrust downwards in a subduction zone

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14
Q

what is an example of a constructive plate boundary ?

A

mid Atlantic ridge

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15
Q

what is an example of a destructive plate boundary ?

A

Nazca plate and South American plate - andes mountains

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16
Q

what is an example of a conservative plate boundary ?

A 
Pacific plate (faster) and North American plate (slower) 
San Andreas fault
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17
Q

What’s an example of a collision boundary ?

A

Indian plate and Eurasian plate

Himalayan mountains

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18
Q

What activity happens on constructive plate boundaries?

A

new crust
submarine volcanoes which may become islands
Ridges

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19
Q

What activity happens on destructive plate boundaries ?

A

Composite volcanoes
Fold mountains
Earthquakes- depth up to 700km
Trenches

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20
Q

What activity happens at conservative plate margins ?

A

Shallow/ medium focus earthquakes

Ridges and scars on surface

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21
Q

What activity happens on collision plate margins ?

A

Fold mountains
Plateaus
Shallow focus earthquakes

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22
Q

What happens at constructive plate margins ?

A

Decompression in the asthenosphere due to gap between the plates enables magma to rise, it cools and spreads up to form new crust. Rifting creates undersea valleys.

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23
Q

What happens at a destructive plate margin ?

A

Hydration melting happens in subduction zone- water involved lowers melting temp. Parallel to plate, unstable mantle material forces itself to the surface. In the Benioff zone, crust rocks melt and chemical reactions occur at the high temps and pressures. Slab pull pulls the oceanic plate down.

24
Q

What happens at a collision plate boundary ?

A

Faulting at connection of 2 plates leads to v wide, mostly shallow, earthquake zone. Slab pull pills down the continental plate. Both plates are the same densities, leading to fold mountains.

25
Q

what are jokulhaups ?

A

A heavy and sudden flood caused when the heat of a volcanos eruption melts the snow and ice in a glacier.

26
Q

What is the elastic rebound theory ?

A

The process of strain, stress, and failure, in a locked fault.

27
Q

What is a locked fault ? And example

A

A fault that is not slipping because the frictional resistance of the fault s greater than the shear stress across the fault. e.g. The 2004 Indian Ocean tsunami was the result of a mega thrust locked fault.

28
Q

on a general level, what do earthquake waves cause?

A

crustal fracturing
ground shaking
secondary hazards (liquefaction and landslides)

29
Q

what are the primary hazards of volcanoes?

A

lava flows
pyroclastic flows
ash falls
gas eruptions

30
Q

What activity happens at divergent oceanic-oceanic plate boundaries ?

A

Rising convection currents bring magma to the surface resulting in small, basaltic eruptions creating a new oceanic plate.
Minor, shallow earthquakes.

31
Q

What happens at divergent continental- continental plate boundaries?

A

Caused by a geologically recent mantle plume splitting a continental plate to create a new ocean basin.
Basaltic volcanoes and minor earthquakes.

32
Q

What happens at convergent oceanic-oceanic plate boundaries ?

A

One oceanic plate is subducted beneath another, generating frequent earthquakes and a curving chain of volcanic islands -violent eruptions.

33
Q

What key discoveries developed the theory of plate tectonics ?

A

1) wegener, 1912
2) Holmes,1930s
3) the discovery of the asthenosphere in 1960
4) magnetic stripes discovery in 1960s
5) Tuzo Wilson,1965

34
Q

What did Holmes do?

A

Had ideas that earth’s internal radioactive heat was the driving force of mantle convection that could move tectonic plates.

35
Q

What did tuzo wilson do?

A

Recognised transform faults

36
Q

What happened at the plate boundary of Nepal 2015?

A

Collision zone cut by huge thrust faults that generate shallow, high magnitude earthquakes.

37
Q

What is a disaster ?

A

500 or more deaths (UN)

38
Q

What is a mega disaster ?

A

Over 2000 deaths OR
Over 200,000 made homeless OR
GDP reduced by 5% OR
a year or more of foreign aid

39
Q

what is the cause of an earthquake?

A

when plates build up frictional stress until it is released in seismic waves when the tension exceeds its threshold.

40
Q

how does a tsunami form?

A

landslides, underwater volcanoes, or underwater earthquakes displace sea bed vertically-column water displacement-grow in shallower water because energy gets compressed.

41
Q

what is the evidence supporting plate tectonics?

A

wegener
seismic waves determine mantle is semi plastic
ocean floor mapped-ridges, mountains, volcanoes
world map of tectonic hazarsds reveals pattern
seafloor spreading
GPS

42
Q

what is an example of a megathrust earthquake?

A

2004 indian ocean tsunami caused by megathrust locked fault. (MMS 9.2)

43
Q

what are p waves?

A 
arrive 1st
fastest waves
can move through solid+liquid
longitudinal-compress in direction of travel
cause ground to shake up and down
44
Q

what are s waves?

A

arrive second
only travel through liquid
up+ down movement of particles- tranverse wave
cause ground to shake side to side

45
Q

what are rayleigh waves?

A

surface waves-only travel through surface or crust in rolling motion
responsible for most shaking felt by people

46
Q

what are love waves?

A

fastest of surface waves land moves side to side in L like the one im gonna take in biology if they ask any 3.1

47
Q

how hot can a lava flow be?

A

1200C

48
Q

how fast can a pyroclastic flow go?

A

700km/h

49
Q

what toxic gases are emitted from a volcano?

A 
CO2
SO2
HCl
CO
H2S (hydrogen sulphide lol @chemistry)
50
Q

what are the 2ndary hazards of earthquakes?

A

lahars

jokulhaup

51
Q

what is a lahar?

A

masses of mud, rock and water (water and tephra) that travel down slopes of volcano. largest can be 100s of ms wide. impossible to outrun-v fast.

52
Q

what is jokulhaup?

A

heavy+sudden flood caused by the heat of a volcanic eruption heating the snow+ice of a glacier. suddenly release large amounts of water, rock, gravel, and ice.

53
Q

what are the primary hazards of earthquakes?

A

crustal fracturing

ground shaking

54
Q

what are the 2ndary hazards of earthquakes?

A

liquefaction

landslides

55
Q

what is liquefaction?

A

loosely packed grains of soil held together by friction, pore spaces filled with water. shaking destabilises soil by increasing space between grains-structure lost. soil loses ability to support building foundations-buildings and roads tilt and sink.

56
Q

why does liquefaction differ in different bedrock?

A

seismic waves travel at different speeds with different amplitudes.
bedrock-high frequency low amplitude waves (less destructive)
saturated sediment-low frequency high amplitude waves (more destructive)

Tectonics (3 decks)

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