EQ1 Tectonics

Question 1

What was Alfred wegeners theory

Answer 1

Continental drift

Question 2

Evidence for continental drift

Answer 2

• Truncated geological features
• continents fit together
• paleoclomactic indicators
• fossils found across continents

Question 3

What are convection currents

Answer 3

Hot rocks heated by mantle rise
Cool rocks sink as more dense

Question 4

Plate boundary types

Answer 4

Conservative - plates move parallel to one another
Constructive - plates more away from eachother and new land forms where hot magma rises
Destructive- ocean and and plates move towards eachother, oceanic plate subducted as is denser
Collision - two land plates move towards eachother

Question 5

features at each boundary

Answer 5

Desmuctive - volcano, earthquake, fold mountain
Conservative - earthquakes
Collision - gold mountain, earthquakes
Constructive- volcanoes, fold mountains, earthquakes

Question 6

What is slab pull?

Answer 6

Gravity acting on dense plates being subducted

Question 7

What is mantle drag

Answer 7

Friction acting on plates as thick viscous mantle moves underheitnand drags at lithosphere

Question 8

What is ridge push

Answer 8

Driving force for plate motion that occurs mid ocean ridge
Newer plates less dense so rise to form ridges
Elevation causes gravity to pull them away from older plates
Plates slide down into asthenosphere

Question 9

What is paleomagnetism

Answer 9

Study of ancient magnetism preserved in rocks
Allow former latitudes to be determined by measuring direction of magnetism in iron bearing minerals

Question 10

How is paleomagnetism applied in plate tectonics

Answer 10

Sea floor spreading at divergent boundaries
Variations in magnetic field show striped pattern across ocean floor
Confirms newest rock along ridge and older rock progressively further away

Question 11

What is a hotspot

Answer 11

Extra hot region deep in mantle

Question 12

What is a mantle plume

Answer 12

Heat rising from hotspot through convectional processes
Facilitates rock melting at base of lithosphere, rises to form volcanos

Question 13

What is subduction?

Answer 13

Destructive boundary Oceanic lithosphere is recycled into mantle

Question 14

Difference in subduction angle

Answer 14

Shallow angle results in belt of deformation characteristic see by crustal thickening and mountain building

Steep angle characterised by formation of back arc basins

Question 15

epicentre and hypocentre

Answer 15

hypocentre- the point within the earth that the rupture starts
epicentre- the point at the surface of the earth above the hypocentre

Question 16

seismic waves

Answer 16

waves that transmit energy released by an earthquake

Question 17

secondary impact- soil liquefaction

Answer 17

– Christchurch 2010
surface rock loses strength and become like liquid due to violent shaking
causes buildings to tilt, settle or even collapse
short term impact on delivery of aid, LT impact on recovery costs

Question 18

secondary impact- lateral spreading

Answer 18

when sloping ground slides across liquefied layer
creates large fissures and cracks in ground surface

Question 19

secondary impact- quake lakes

Answer 19

landslides block rivers and cause flooding
water collects quickly, flooding huge areas
aftershocks collapse natural dams, sending a torrent of water

Question 20

secondary impact- landslides/ avalanches

Answer 20

2010 Christchurch, 2010 Nepal
occur when magnitude 4<
slopes weaken and fail, made more likely by heavy rain or fractured rock
around 70% of all earthquake deaths caused by landslides

Question 21

secondary impact- fire

Answer 21

Kobe Japan 1995, Indonesia 2009
caused by fractured gas mains
hard to out out due to fractured water mains

Question 22

secondary impact- Tsunamis

Answer 22

Japan 2011
Generated by earthquakes under the ocean displace large amounts of water

Question 23

secondary impact- comms and infrastructure destroyed

Answer 23

San Fransisco, USA
road and rail links, telephone masts and wifi
hampers rescue efforts, causes injury and loss of life

Question 24

secondary impact- disease

Answer 24

Indonesia 2004
lack of water and sanitation cause cholera and dysentery to spread quickly
dead bodies add to risk when buried

Question 25

why do intra-plate earthquakes occur

Answer 25

- reactivation of old fault lines - subsidence from mining or fracking - pressure on surface rocks from water in reservoirs - large manmade explosions - large avalanches and landslides

Question 26

what is a megathrust earthquake

Answer 26

after frictional stress has built from plates locked together for some time and failure occurs

Question 27

what is the benioff zone

Answer 27

where plates converge and one is subducted different speeds of rock create numerous deep-focused earthquakes determines position and depth of hypocentre

Question 28

where to seismic waves originate

Answer 28

Benioff zone

Question 29

3 ways to measure an earthquake

Answer 29

- Richer scale- vibrations plotted on a seismometer, numbered 0-10 - Moment magnitude scale- moment is product of distance moved and force required to move it - Mercalli scale- measures damage, based on visual or experienced effects. ranges from unnoticeable shaking to catastrophic damage

Question 30

Characteristics of P waves

Answer 30

First wave to arrive at seismic recording stations Compresses and expands land (moves backwards and forwards) in the direction of travel

Question 31

Characteristics of S waves

Answer 31

Travel through solids Secondary because Second to arrive at seismic recording stations Shake the ground side to side perpendicular to the direction of wave travel

Question 32

Characteristic of Rayleigh waves

Answer 32

Surface waves Travel in rolling motion like ocean waves Can travel through solids Slow moving

Question 33

Characteristic of a love wave

Answer 33

Surface waves Travel through solids - not liquids Horizontal motion that moves surface from side to side perpendicularto direction wave is travelling

Question 34

What conditions are needed for formation of a volcano

Answer 34

Partially molten rock, magma below surface of the earth. Rises through natural cracks in crust, or gets safer underground while pressure rises until it erupts explosively

Question 35

What is tephra

Answer 35

Solid material, ranging from volcanic bombs to ash particles ejected into the atmosphere

Question 36

What are pyroclastics

Answer 36

Very hot gas charged material, includes gas and tephra

Question 37

Name some volcanic gases

Answer 37

Carbon dioxide, carbon monoxide, hydrogen sulphide, sulphur dioxide, chlorine

Question 38

Name primary effects / processes of a volcanic eruption

Answer 38

Tephra, pyroclastic flows, lava, volcanic gases

Question 39

Name secondary effects in a volcanic eruption

Answer 39

Lahars, flooding, tsunamis, volcanic landslides, Short term climate change, jokulhlaup

Question 40

What are lahars

Answer 40

Volcanic mud flows

Question 41

Why do volcanos cause flooding

Answer 41

Melting of icecaps and glaciers

Question 42

What is a jokulhlaup

Answer 42

Glacial melting outburst floods

Question 43

How to volcanos form tsunamis

Answer 43

Caldera forming events (eg Krakatoa) generate giant waves

Question 44

How to volcanos cause short term climate change

Answer 44

Inject vast amounts of debris into the atmosphere which reduced global temperatures

Question 45

Difference between dormant, active and extinct

Answer 45

Active = still erupts Dormant= not currently erupting but supposed to erupt again Extinct = won’t erupt again

Question 46

What are the 3 landform characteristics of volcanos

Answer 46

Shield= wide and gentle slopes, runny lava Stratovolcano= steep sloping side built up over millions of years with compositions, typically more violent Calderas =large couldron hollow forming after magma chamber empties in volcanic eruption, ground collapses leaving a depression at the surface

Question 47

What types of eruption are there

Answer 47

Explosive- gas driven eruptions nwhich propel magma and tephra Effusive- outpouring of lava without significant explosive eruption

Question 48

What are the three groups of lava

Answer 48

Basaltic Andesitic Rhyolitic

Question 49

How does silica connect affect lava and eruptions

Answer 49

More silica means more gases! More violent, more viscous lava

Question 50

Features of basalt lava

Answer 50

Fluid Low silica content Basic Hottest lava Produces shield volcanos- wide with low slopes Located at divergent margins and hotspots Effusive

Question 51

Andesite lava

Answer 51

Viscous Medium silica content Medium heat Produces steep sided cones Convergent margins Violent and explosive

Question 52

Rhyolitic lava

Answer 52

Viscous Hugh silica content Lowest heat around 900°C Produces steep sided cones Convergent margins Explosive

Question 53

How many people have died due to eruptions in the last 300 years

Answer 53

250000