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Geography 2016 > Tectonics > Flashcards

Tectonics Flashcards

1
Q

Wegners climatological evidence

A

Coal which must have been formed in tropical conditions found in Uk, Antarctica and USA

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2
Q

Wegners geological evidence

A

Glacial deposits found in India South America and Antarctica
Striations in same directions in Brazil and west Africa

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3
Q

Wegners continental evidence

A

Appeared fit of the continents and shorelines

Seen as Africa and South America

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4
Q

Two types of constructive margin

A

Oceanic-oceanic
Continental- continental
Plates move apart

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5
Q

Landform found at oceanic divergent boundaries + example

A

Oceanic ridges

Mid Atlantic ridge as North American plate moves away from Eurasian plate

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6
Q

How are oceanic ridges formed?

A

Constructive oceanic plate boundary
As plate moves apart at vary rates, the crust expands and becomes weaker
Increased heat at the surface and eventually the brittle crust subsidies into magma and forms ridge

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7
Q

Landform at continental divergence and example

A

Rift valleys
East African Rift Valley
Nubian-Somalian

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8
Q

How are Rift Valleys made?

A

As 2 continental plates move apart the brittle crust fractures and sinks at parallel faults towards the lithosphere

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9
Q

Form, lava type and eruption style of volcanoes at oceanic divergent boundary + example
VEI

A 
Lava plateaux/fissure 
Basaltic 
Icelandic 
Typically submarine volcanoes but can reach surface 
Surtsey 
VEI:0-2
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10
Q

Wegners biological evidence

A

Fossils of Mesosaurus found in South America and South Africa with migration unlikely

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11
Q

Volcanicity at continental divergent margins

A 
Example Mount Kilimanjaro 
Form: basic shield volcano 
Lava: basaltic 
Eruption: Hawaiian possibly Vesuvian 
VEI: 0-2
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12
Q

Volcanicity at continental divergent margins

A 
Example Mount Kilimanjaro 
Form: basic shield volcano 
Lava: basaltic 
Eruption: Hawaiian possibly Vesuvian 
VEI: 0-2
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13
Q

What is a transform fault?

A

90 degrees to plate boundary as new crust is formed

As pressure builds can result in an earthquake

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14
Q

Can earth quakes occur at divergent plate boundaries?

A

Yes

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15
Q

3 types of destructive plate boundary

A

Oceanic-oceanic
Oceanic-continental
Continental-continental

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16
Q

Landforms at O-C destructive boundary

A

Deep sea trench

Fold mountains

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17
Q

How are deep sea trenches formed?

A

O-C destructive
O-o destructive
Peru chile trench as max a subducted under South American
Marianas trench as Pacific subducted under Philippine

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18
Q

How are fold mountains formed

A

O-C destructive
C-C destructive margins
As plates come together sediments are deformed by faulting and forming and are uplifted to form fold mountains

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19
Q

What is the Benioff zone?

A

Part of the subduction zone

Point at which the oceanic plate is melted/ destroyed

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20
Q

Volcanic activity at O-c destructive margins

A

Oceanic plate descends towards the mantle and becomes hotter
Increased friction also increases heat
Results in plate melting
Lava erupted in gaps in crust in volcanoes

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21
Q

Why is lava andesitic at o-c destructive margins

A

Oceanic plate melts which is typically basaltic but it combines with older elements of the crust which have a higher silica content

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22
Q 
Form 
Lava type 
Eruption style 
VEI 
Volcanoes at O-C destructive margins
A

Composite cone or ash and cinder cones
Andesitic lava
Peléan eruptions
VEI 4-6

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23
Q

What % of active volcanoes are found at subduction zones

A

80

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24
Q

Do earthquakes occur at O-O destructive margins

A

Yes typically shallow focus
Very powerful
Up to magnitude 9

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25
Is there volcanic activity at C-C destructive margins
No as no subduction | Few earthquakes occur
26
What are conservative plate margins
Plates move parallel to the boundary No crust is made or destroyed No volcanic activity Pressure builds and released as earthquakes
27
Example of a conservative plate boundary
San Andreas fault California | Pacific against North American
28
What are hotspots
Volcanic activity that does not occur at plate boundary Concentration of radioactive elements increases heat Generates convection currents More magma near surface eats into plate above Lava breaks into surface
29
Is a hotspot stationary or moving?
Stationary
30
Where are volcanoes found
Oceanic ridges Oceanic trenches:/ subduction zone Rift Valleys Hotspots
31
What is intrusive volcanic activity
Magma which is viscous does not reach surface and cools and intrudes the crust to form features
32
How are intrusive features exposed
Erosion and weathering
33
Batholith formation
Large mass of magma cools and solidifies Forms granite crystals in Igneous rock Formed as a dome
34
Example of a batholith
Dartmoor | Isle of Arran
35
What is a metamorphic aureole?
During batholith formation the surrounding rock is altered by heat and pressure of the magma intrusion Dynamics of rock change eg limestone to marble
36
Laccoliths
Small injections of magma in rock strata Causes the rock to arch upwards Forms a lens shape
37
Example of a laccoliths
Eildon hills Scotland
38
What is a dyke
Vertical intrusion with horizontal cooling cracks Magma shoots upwards when forming a batholith Cut across the bedding Plane of rock which has been previously intruded
39
Collection of dykes
Dyke swarm
40
Example of a dyke
Isle of Skye
41
What are sills
Horizontal intrusions with vertical cooling cracks | Run along the bedding plane
42
Example of a Sill
Great Whin Sill Scotland
43
What are extrusive landforms
Molten rock reaches the surface
44
Solfatara | Example
Gases mainly sulfur escape onto the surface from a dormant volcano Bay of Naples, Italy
45
Geysers
Large discharge of water followed by steam Water is heated by the contact with hot rock and then constricted and pressurised Plumbing system allows a jet of water Old Faithful Yellowstone
46
Mud volcanoes
Deposition of hot water and mud onto the surface, not dangerous Philippines
47
Fumaroles
Superheated water changes state into steam as a result of a large pressure decrease Gases such as CO2 and SO2 released
48
Examples of intrusive and extrusive activity in the UK
Granites Dykes and sills Basaltic flows Volcanic plug
49
Granites in UK
Intruded rock in the Grampians Batholiths exposed Tors made= distinctive landscape
50
Dykes and sills in the UK
More resistant than surrounding rock | Great Whin
51
Basaltic flows UK
Antrim lava plateaux in N Ireland
52
Volcanic plug UK
Long extinct volcano found in Edinburgh | Active 300mn years ago
53
Primary impacts of volcanic activity
Tephra Pyroclastic flows Lava Volcanic gases
54
What is tephra
Solid material ejected from a volcano | Range from ash to volcanic bombs
55
Pyroclastic flows
Gas charged, high velocity flows of tephra and gas
56
Examples of volcanic gases | Example
``` Sulfur dioxide Carbon dioxide Carbon monoxide Chlorine 1700 suffocated in Nyos Cameroon ```
57
Example of volcanic gases
1986 Nyos Cameroon 1700 suffocated
58
What are lahars?
Volcanic Mud flows
59
Example of lahars
Village of Amero Colombia destroyed in 1985
60
Why is flooding a secondary effect of volcanoes and example
Melting of glaciers Iceland 1996
61
Example of volcanic tsunami
Krakatoa 1883 36,000 people drowned
62
Example of climate change due to volcanoes
Krakatoa caused 0.5degree global drop in temperature
63
Final secondary effect
Landslides
64
Focus of earthquake
point at which the pressure of plate movement has been released
65
Epicentre of an earthquake
Point directly above the focus on the earths surface
66
Depth of a shallow focus
0-70km
67
Which waves travel fastest
p
68
Movement of P waves
Compressional | Vibrate in direction that they travel
69
Which of the Earth's layers can P waves travel through
Mantle and core
70
Can P waves travel through solids, liquids or both
Both
71
At what speed do s waves travel
1/2 speed of P
72
Movement of S waves
shear rock as they vibrate at 90 degrees to the direction of travel
73
Can S waves travel through solids, liquids or both
Solids only
74
Which of the Earth's layers can S waves travel through
Mantle
75
2 types of surface wave
Love and Rayleigh
76
Speed of Surface waves
travel slowest and nearest to the Earth's surface
77
Describe L waves
travel through solids only and move side to side and result in rock shearing
78
Describe Rayleigh waves
Travel in a rolling motion and through liquids and solids
79
What are the 4 causes of earthquakes
Plate Movement, Reactivation of old fault lines, subsidence and pressure on rocks through reservoirs and fracking
80
Example of reactivation of fault line quake in Uk
4.8 in Birmingham 23/09/2002
81
Are destructive or constructive earthquakes the most powerful
Destructive
82
Describe the Richter Scale
Logarithmic scale where an increase of 1 on the scale translates to 10 higher amplitude and 31 times more energy released
83
Mercalli Scale
measures the intensity of an earthquake using observations eg photos to assess the damage caused

Geography 2016 (4 decks)

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