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School Revision > Geo - Tectonic plates > Flashcards

Geo - Tectonic plates Flashcards

1
Q

tectonic plates

A
  • large slabs of solid rock that floats on the mantle
  • constantly move
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2
Q

layers of the earth

A
  1. crust
  2. mantle
  3. outer core
  4. inner core
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3
Q

crust

A
  • a layer of sand and rock
  • 5-50km thick
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4
Q

mantle

A
  • 2850km thick
  • reaches about half distance to the center of the earth
  • hot enough to liquify and become slow moving molten rock or magma
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5
Q

outer core

A
  • mass of molten iron
  • 2200km thick
  • surround the solid inner core
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6
Q

inner core

A
  • mass of iron
  • 3870oC
  • iron melts at this temp but immense pressure keeps it solid
  • 2400km in diameter
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7
Q

movement of plates

A

convection currents

core heats rock in mantle => hot semi-molten rock becomes less dense than its surrounding and rises => semi-molten rock reaches the crust above => semi-molten rock spreads out carrying the plates above it (conveyor belt) => semi-molten rock cools and sinks back down to be re-heated

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8
Q

2 types of crusts

A
  1. oceanic crust
  2. continental crust
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9
Q

oceanic crust

A
  • 6km (4 miles) thick
  • 200 million years old
  • made of basalt
  • density: 3g/cm
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10
Q

continental crust

A
  • 6 to 47 miles in thickness depending on location
  • 1 to 4 billion years old
  • made of granite
  • density: 2.6g/cm
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11
Q

where do earthquakes happen

A
  • margins / boundaries of tectonic plates
  • pacific ring of fire
  • hotspots (areas under the crust where magma is hotter than surrounding magma)
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12
Q

pacific ring of fire

A
  • string of tectonic activity
  • 90% of all earthquakes
  • 75% of all active volcanoes on Earth
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13
Q

4 types of plates boundaries / margins

A
  1. constructive boundaries
  2. conservative boundaries
  3. destructive boundaries
  4. destructive boundaries - collision zones
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14
Q

constructive boundaries

A

plates are moving apart (convection currents) => magma rises from the mantle => magma erupts to surface of earth (accompanied by earthquakes) => magma reaches the surface and cools => solidifies to form new crust of igneous rock => repeated

  • new rocks builds up to form a volcano
  • constructive boundaries tend to be found under the sea, eg. mid Atlantic
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15
Q

conservative plate boundary

A

slide in opposite direction / same direction different speed => plates move and create friction and get stuck => pressure builds => pressure releases and sends out huge amounts of energy => causes earthquake

  • earthquakes on conservative plates can be destructive bec occurs to earths surface
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16
Q

destructive boundaries

A
  • oceanic plate and continental plate

o.p and c.p collide => o.p forced beneath the c.p (subduction) => results in ocean trench => plate sinks into mantle and melts into magma => pressure builds up beneath earth surface => magma escapes thru weaknesses in rock and rises up thru a composition volcano (stratovolcano)

  • volcanic eruptions are often violent with steam, gas and ash
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17
Q

destructive boundaries - collision boundaries

A

2 continental plates collide => weigh the same so both are forced up => forms fold mountains

  • can be very powerful and destructive
  • landslides can be triggered by earthquakes
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18
Q

how are volcanoes formed

A
  • rupture in the crust of the earths
  • allows hot lava, volcanic ash and gases to escape from a magma chamber below the surface
  • volcanoes are most found where tectonic plates are diverging / converging and most are underwater
19
Q

main features of a volcanoes

A
  • ash cloud
  • pyroclastic flow
  • crater
  • main vent
  • lava flow
  • magma chamber
  • secondary vent
  • secondary cone
  • volcanic bombs
20
Q

2 types of volcanoes

A
  1. composite volcanoes
  2. shield volcanoes
21
Q

composite volcanoes

A
  • found at destructive plate margins
  • steep sides
  • made up of alternate layers of ash and lava
  • doesn’t flow far, sticky acidic lava
  • eruptions can be violent
22
Q

shield volcanoes

A
  • constructive plate margins
  • wide base
  • gentle sloping sides
  • lava is runny, flows a long way, basic (opposite acidic)
  • frequent eruptions
  • not violent
23
Q

why do people live near volcanoes

A
  1. geothermal energy
  2. tourism
  3. mining
  4. farming
24
Q

geothermal energy - volcanoes

A
  • energy created by using steam from underground
  • steam drives turbines in stations
  • energy for domestic and industrial use.
  • cheap and environmentally friendly
25
Q

tourism - volcanoes

A
  • scenery attracts tourists
  • creates many jobs for local people (tour guides, restaurants, hotel, gifts shops)
26
Q

mining - volcanoes

A
  • brings earths riches to the surfaces
  • minerals in lava underground can be mined when cooled (gold silver, diamonds, copper, zinc)
  • can be dangerous to work in
27
Q

farming - volcanoes

A
  • soil is mineral-rich and fertile
  • ideal for farming
  • will produce healthy crops and high yield harvests

soil naturally contains
- potash
- nitrogen
- sulphur

28
Q

causes of earthquakes

A
  • movement of the tectonic plates
  • seismic waves (shock waves like ripples on a pond)
  • more damage occurs near the epicenter (directly above the focus)
29
Q

how do earthquakes happen

A

plates are constantly moving => friction the plates become stuck => pressure builds => pressure release and sends huge amounts of energy => earths surface shake violently (earthquake)

30
Q

how are earthquakes measured

A

seismometers

31
Q

seismometers

A
  • detects seismic waves
  • recorded by a series of zig-zags
  • can determine time, location and intensity of an earthquake
32
Q

Richter scale

A
  • measures the magnitude of a tremor
  • scale of 1 to 10
33
Q

factors of how severely a country is impacted

A
  1. geographical location
  2. level of development - predict / prepare for hazards
  3. magnitude - scale of the hazard
  4. natural factor
  5. population distribution - lower no of deaths
  6. time
  7. education - allow more people to survive
  8. frequency - how often hazard occurs
34
Q

how do countries reduce the impacts of an earthquakes

A

3 P’s
1. prediction
2. protection
3. preparation

35
Q

prediction - 3 p’s

A
  • use of seismometers
  • can predict where and when they will happen
36
Q

protection - 3 p’s

A
  • building adjustments
  • rubber shock absorbers
  • steel frames
  • assembly area
  • lightweight roof
  • safety glass
37
Q

preparation - 3 p’s

A
  • earthquake drills
38
Q

montserrat

A

location: the Caribbean
area: 12km - 8km
population: 11000
capital: Plymouth
tectonic plates: Caribbean and north American plates, destructive plates
volcano: Soufriere hills volcano, composite

39
Q

cause of eruption - Montserrat

A

destructive plates
…
oceanic plate and continental plate

40
Q

info about eruption - montserrat

A
  • began 18 July 1995
  • Plymouth was evacuated bec pyroclastic flows and mudflows began occurring
  • built a huge lava dome, lava was sticky and couldn’t flow
  • lava dome became unstable and collapsed
  • hot fast moving avalanches of lava blocks, gas and dust
  • pyroclastic flow travelled down mosquito ghaut
  • pyroclastic flow couldnt be controlled by the ghaut and spilled out of it
  • killed 19 people, several others were burned
41
Q

primary effects - montserrat

A
  • 2/3 island was covered in ash
  • couldnt aid to people
  • ash polluted the air
  • over populated the evacuation place
  • forest fires & tsunamis caused by pyroclastic flow made more damage
  • only airport was closed
  • poor sanitation
42
Q

secondary effects- montserrat

A
  • eruption destroyed two main industries; tourism and farming
  • ash covered field killed crops
  • farmers had no income
  • vegetation was destroyed by acid rain
  • polluted lakes and rivers, animal life almost impossible
  • population decreased, making it difficult for the country to recover (11,000 ppl to 4,000)
43
Q

immediate / long term responses- montserrat

A
  • MVO (montserrat volcano observatory) was set up to monitor the volcano / predict eruptions
  • scientists prevented progression in island for they believed another eruptions would have wiped out the whole island (no investment went to waste)
  • risk map was devised to show residents where it was safe on the island
  • 41 million dollars will donated by the British government to help the nation rebuild the island
  • 24 thousand was given to individual families as financial aid
44
Q

why do people still live near the montserrat

A
  • adventure tourism
    => tourists visit ruins and towns which are still buried in ash
  • geothermal energy
    => plans to increase geothermal energy
  • volcanic sand
    => exports sand for construction
  • beaches
    => distinctive ‘black sand’
  • poverty
    => no income to move countries

School Revision (34 decks)

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