enquiry 1 Why are some locations more at risk from tectonic hazards

Question 1

Hazard

Answer 1

the potential threat to human life

Question 2

natural hazard

Answer 2

can be:
hydro-meteorological (climatic processes)
geophysical (land processes)

Question 3

Divergent constructive (continental)

Answer 3

2 continental
magma plume pushes up and causes the crust to fall = rift valley
fluid basaltic magma from upper asthenosphere reaches the surface
east Africa rift valley

Question 4

Divergent constructive (oceanic)

Answer 4

magma pushes up and out of the surface
grows as new molten rock takes its place
magma is from the partial melting of the asthenosphere
fluid basaltic lava
VEI 1-3
effusive and frequent 
mid-Atlantic ridge

Question 5

Convergent collision

Answer 5

2 continental with same density move together
crumple and fold 
fold mountains 
Himilayas 
usually no associated tectonic hazard

Question 6

Convergent destructive

Answer 6

denser oceanic sinks under continental
melt in subduction zone into andesitic explosive magma
slab pull speeds up the process
high on the VEI 
magnitude 7-9 earthquakes
triggers tsunamis
less frequent

Question 7

Conservative

Answer 7

2 continental move past each other
friction builds and slips
shallow focus
San Andreas

Question 8

Benioff zone

Answer 8

area of deep earthquakes

Question 9

elastic rebound theory

Answer 9

Locked fault
stress builds
stress exceeds threshold= failure
strain energy releases seismic waves

Question 10

Volcanoes

Answer 10

all plate boundaries
highest magnitude= conservative
pacific ring of fire= 70%
intra-plate earthquakes= middle/interior of plate (Hawaii)

Question 11

Tsunamis

Answer 11

secondary hazard associated with earthquakes

destructive only

Question 12

volcanoes

Answer 12

violence depends on amount of gas in magma and how easily it can escape
more explosive = convergent and divergent
composite
less explosive= constructive and divergent
shield
P waves= immediate shock
S waves=longer wavelengths and arrives seconds later
L waves=travel through crust (crustal fracturing and secondary hazards like landslides)

Question 13

palaeomagnetism

Answer 13

The 1960s
showed magnetic patterns were arranged in direction of earths magnetic field
used to date the age of the crust
mid-Atlantic ridge

Question 14

convection currents

Answer 14

hot core heats up rock in lower mantle

hot rock rises slowly

as it rises it slowly cools and cant rise due to solid crust so it goes sideways

cools further and falls back down

Question 15

plate tectonic theory

Answer 15

earths crust divided into plates
radioactive reactions occur in core= convection currents
at mid-ocean ridges = slab push and pull (Pacific plate)

believed to be correct due to:
Wegners CONTINENTAL DRIFT THEORY
seismic waves- Benioff zone shows subduction of oceanic crust

Question 16

sea-floor spreading

Answer 16

sea floor widens

Question 17

secondary hazards

Answer 17

soil liquefaction leads to lateral spreading which creates fissures (damages roads)

Landslides- travel several miles and grow in size
rarely occur at less than mag 4
exacerbated by saturated ground (2015 Nepal summer monsoon rain)

Question 18

Mantle plumes

Answer 18

Concentrated areas of heat convection

At plate boundaries they are sheet like

Hot spots they are column like

Question 19

Plate boundary

Answer 19

The narrow linear zone where two tectonic plates meet

Question 20

Arthur Holmes 1930s

Answer 20

Earths internal radioactive heat was driving force of mantle convection that move tectonic plates

Question 21

Tuzo Wilson 1965

Answer 21

Transform faults

Question 22

Epicentre

Answer 22

Point in the earths surface directly above the focus

Question 23

Crustal fracturing

Answer 23

2004 Indian Ocean created a rupture line for up to 1000km

Energy pulses generated along entire daily length

Question 24

Pyroclasts

Answer 24

Any rock fragments ejected from a volcano (ash/tephra)

Question 25

Volcanic hazards

Answer 25

Jokulhlaup- floods caused when volcano erupt beneath glaciers and ice caps (common in Iceland)

Gas eruption- eruption of co2 and sulphur dioxide which can poison people (composite/shield)

Ash fall- ash particles and larger tephra particles can blanket huge areas, killing veg/ collapsing buildings/ poisoning water courses (constructive plate margin cinder cone or fissure eruption/ composite)

Question 26

Deadly tsunamis

Answer 26

2004 Indian Ocean

Magnitude 9.2

Wave height 24m

Deaths 230,000

2011 Japan

Magnitude 9

Wave height 9.3m

Deaths 16,000

Question 27

Tsunami generation

Answer 27

Sub marine earthquake displace sea bed vertically

Result of movement along a fault line at a subduction zone

Displaced large volume of water in ocean water column

Moves outward in all directions from point of displacement

Moves as ‘bulge’ in open water

Usually hit coast as ‘wave train’