tectonics

Question 1

where can earthquakes and volcanoes occur

Answer 1

• most activity is found in zones along the plate boundaries

Question 2

what are intra-plate earthquakes

Answer 2

• earthquakes that occur near the middle of plates
• associated with ancient faults, which resulted from the solid crust cracking

Question 3

why do some volcanoes occur in the middle of plates

Answer 3

• at hotspots
• either the result of the upwelling of hot molten material from the core/mantle boundary (e.g. Hawaii, Pacific Plate) or from the top of a huge mantle plume just under the crust (e.g. African Plate)

Question 4

what boundaries are the most powerful earthquakes associated with

Answer 4

convergent/destructive or conservative

Question 5

what is the oceanic fracture zone

Answer 5

a belt of activity through the oceans along the mid ocean ridges, coming onshore in Africa, the Red Sea, the Dead Sea riff and California

Question 6

what is the continental fracture zone

Answer 6

a belt of activity following the montain ranges from Spain, via the Alps, to the middle East, the Himalayas

Question 7

where is volcano activity found

Answer 7

• along divergent oceanic ridges e.g.mid-Atlantic ridge
• along riff valleys
• near subduction zones - e.g. the Pacific ring of fire
• over hot spots e.g. Hawaiian islands

Question 8

what is a convergent plate boundary

Answer 8

when two plates move toward each other

Question 9

what is a divergent plate boundary

Answer 9

when two plates move away from each other

Question 10

what is a transform plate boundary

Answer 10

when two plates slide past each other

Question 11

what is subduction
which plate boundary does it occur at

Answer 11

when one plate is more dense than another, the more dense plate does underneath the less dense one
occurs at convergent plate boundaries

Question 12

explain collision boundaries

Answer 12

when two plates are the same material (and same denseness). when they hit, the both buckle up
making fold mountains
e.g. Mount Everest

Question 13

examples of rift valley and mid-ocean ridge

Answer 13

great rift valley - Africa
mid-atlantic ridge - Atlantic ocean

Question 14

what hazard do transform boundaries create

Answer 14

earthquake
e.g. California - Pacific plate slides past the North American plate

Question 15

what is a chain of volcanic islands callled

where are they found

Answer 15

island arcs
found on destructive boundaries when two plates are moving together
e.g. Aleutian islands

Question 16

how is a hotspot formed

Answer 16

• extreme heat from the core magma plume is heated by the core
• convection causes heat and material to move up the mantle
• when the mantle plume reaches the crust it melts to make the crust thinner
• molten rock finds its way to the surface through fisssures in the crust
• lava flows create seamound and over time these reach the surface as islands
• as the plate moves, the hotspot volcano leaves behind the magma plume

Question 17

what is slab pull

Answer 17

• today seen as a major driving force for plate movement
• newly formed oceanic crust at mid-ocean ridges becomes denser and thicker as it cools
• this causes it to sink into the mantle under its own weight - pulling the rest of the plate further down with it

Question 18

what is ridge push

Answer 18

• as the new seafloor cools over time, it becomes mroe dense and slides laterally down slope
• this pushes the plates apart by ridge push

Question 19

what is passive convection

Answer 19

• convectional upwelling of hotter mantle rock below the divergent margins
• the thinning of the plate above due to tension in the plate allows the mantle below to upwell
• this convectional rising is seen as an induced rising, not spontaneous rising that occurs by itself

Question 20

what is decompression melting

Answer 20

• as the mantle rock rises closer to the lithosphere, it experiences a reduction in pressure
• this results in partial melting of the mantle rock
• as the mantle rock is composed of different materials, it does not all melt at once
• the minerals with more silica have lower melting points and so are the first to melt

Question 21

what type of volcano do each plate boundary create

Answer 21

convergent - composite volcano (more violent)
divergent - shield volcano (runny lava)

Question 22

how does viscosity affect strength of eruptions

Answer 22

more viscous –> less fluid –> stronger eruptions

Question 23

palaeomagnetism

Answer 23

• evidence of sea-floor spreading is gained from an examination of the polarity of the rocks that make up the ocean floow
• at regular intervals, the polarity of the earth reverses
• this striped pattern which is mirrored on either side of a mid-oceanic ridge, suggests that the ocean crust is slowly spreading away from the boundary

Question 24

4 pieces of evidence for sea floor spreading

Answer 24

1. active fractures in the lithosphere along the ocean floor, in a pattern that mimics the shapes of the continental coastlines
2. the age of the seafloor rock increases as you get further away from the mid-ocean ridge
3. the thickness of the layer of sedimetns deposited on the ocean floor increases as you get further away from the mid-ocean ridge
4. patterns of seafloor magnetism on either side of mid-ocean ridges match up with one another

Question 25

what is the benioff zone

Answer 25

the boundary where an oceanic plate is undergoing subduction between an overiding continental plate. the sinking oceanic plate is colder than the crust into which it is sinking this causes sudden stress that may trigger earthqyakes within the zone that the subduction oceanic plate is melted

Question 26

state the types of seismic wave

Answer 26

- primary - secondary - rayleigh - love

Question 27

primary waves: speed, movement, depth, effects

Answer 27

- fastest wave - can go through liquids, push waves, can reflect back from the core - travels through the crust - rarely does much damage

Question 28

secondary waves: speed, movement, depth, effects

Answer 28

- second fastest wave - side to side, can reflect back from the core, can't go through liquids - travels through the crust - slightly more damage than primary

Question 29

rayleigh waves: speed, movement, depth, effects

Answer 29

- second slowest - move in a circular rolling motion - travels through the surface - damaging but less destructive than love

Question 30

love waves: speed, movement, depth, effects

Answer 30

- slowest - can't move through liquids - move in all directions (side to side, front to back) - travels through the surface - most destructive

Question 31

what is liquefaction

Answer 31

when a saturated or partially saturated soil loses its strength and integrity as a result of the shaking that occurs during an earthquake

Question 32

state the hazard-risk equation

Answer 32

risk = (hazard - vulnerability) / capacity to cope

Question 33

what are the parts of the Pressure and Release model / crunch model

Answer 33

- root causes e.g. limited access to power and recourses, corrupted government - dynamic pressures e.g. lack of training, population growwth, lack of appropriate skills - unsafe conditions e.g. fragile physical environment. vulnerable society - hazards e.g. earthquakes, flooding

Question 34

Turkey Syria earthquake facts

Answer 34

- rates 7.8 on the Richter scale - occurred in 2022 - initial earthquake was followed by thousands of after shocks, some almost as strong <-- facilities struggling to be improved in between shocks

Question 35

Turkey Syria earthquake impacts

Answer 35

- impacted at lleast 15.73 million people in both Turkey and Syria (over 55,000 lives lsot and nearly 130,000 injured) - Epicentre was located in a Turkish City called Gaziantep containing many poorly constructed properties - overall at least 230,000 buildings were damaged or destroyed across 11 provinces in Turkey - millions left in need of immediate assistance including food, water and shelter - many hazardous substances such as debris and chemicals were released into the air from damaged buildings, contributing significantly to air pollution

Question 36

Turkey Syria earthquake - responses/capability

Answer 36

- government wasn't preapared so even the most basic of needs were not met even weeks after the event - many people left for long periods in difficult conditions - even a year after the event, many citizens are living in container city (essentially just pieces of shipping container) <-- reflects the insufficient recovery of the city - despite slow governmental responses, the countries recieved help from international organisations such as the EU

Question 37

Haiti Earthquake 2010 the event

Answer 37

- 7.0 magnitude earthquake - epicentre was 15km from Port-au-Prince (the capital of Haiti) - focus was just 8km below the surface - shallow earthquake often cause severe ground shaking - caused by stress building up along the transform plate margin

Question 38

Haiti Earthquake 2010 - impact

Answer 38

- there were 2 million people living in the most affected area - 230,000 people died - over 180,000 homes have been damaged or destroyed - 1.5 million people have been made homeless - 19 million cubic metres of rubble and debris in Port-au-Prince - 1.5 million people have ended up living in camps, including over 100,000 at critical risk from storms and flooding - cholera has become a major issue (lack of clean water), with hundreds dying from it - there are over 1100 camps and 54 of these are home to 5000 or more - 600,000 people have left their home area in Port-au-Prince and most are staying with host families - near;y 5000 schools have been damaged or destroyed

Question 39

Haiti earthquake 2010 - responses

Answer 39

- enough emergency shelter, mostly tarpaulins, has been provided for 1.9 million people - three-quaters of the nearly 120,000 buildings that have been inspected so far can be lived in now or repaired - 200,000 people have recieved cash or food for public work - there was one emergency toilet for every 200 survivors - 300 truckloads of rubble and debris a day are being cleared - total cost of rebuilding was estimated $US11.5 billlion, taking 5 - 10 years

Question 40

Haiti earthquake 2010 - UK disaster emergency committee

Answer 40

- provided over 100,000 medical consultations - over 3000 latrines built - clean drinking water has been provided for over 250,000 people - supplementary feeding has supported 1890 malnourished children

Question 41

Mount Pinatubo 1991 - Philippines

Answer 41

- one of the biggest eruptions in the 20th century - everyone within 20 miles of the summit was evacuated - eruption caused ash and molten rock to go thousands of feet in the air - Pyroclastic flows lasted as long as 40 square miles from the volcano - 320 people killed from collapsing roofs and sickness in refugee camps

Question 42

Mount Pinatubo 1991 - philippines secondary effects

Answer 42

- lahars - mud flows - furhter typhoons meant rain mixed with the ash from the eruption --> this caused estensive mud flows which destroy everything in their path and trap people

Question 43

4 parts of the Hazard management cycle

Answer 43

- response (a re-active measure of how a country or community reacts to events) - recovery (another re-active post-event measure in terms of the time it takes for recovery and action plans to be put in place) - mitigation (pro-active strategies put in place before an event occurs to prevent a hazard from occurring) - preparedness (another pro-active method to help increase resilience to a disaster)