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my geography 🌍 > hazardous earth > Flashcards

hazardous earth Flashcards

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1
Q

define lithosphere

A

the upper most layer of the earth - the top of the mantle and the crust

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2
Q

define asthenosphere

A

lower part of the earth’s mantle

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3
Q

how hot is the inner core

A

6000°C

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4
Q

how hot is the outer core

A

5000°C

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5
Q

how hot is the mantle

A

3800°C

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6
Q

how thick is the oceanic crust (km)

A

6-8 km

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7
Q

what is the oceanic crust made of

A

basalt

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8
Q

how thick is the continental crust (km)

A

30-50 km

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9
Q

what is the continental crust made of

A

granite

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10
Q

is the oceanic or continental crust denser

A

the oceanic crust is denser

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11
Q

which type of crust can be destroyed (continental or oceanic)

A

oceanic can be destroyed when two techtonic plates meet

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12
Q

what makes the core so hot

A

radioactive decay of some elements eg
uranium

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13
Q

what is the magnetosphere

A

a huge invisible magnetic field that surrounds the earth, protecting us from harmful radiation from space

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14
Q

what part of the earth produces the earth’s magnetic field

A

the outer core

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15
Q

what is pangea and how long ago did it exist

A

250 million years ago, the continents were once all joined together as one large supercontinent

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16
Q

give two points as to how we know that pangea existed

A
  • there are the same fossils in different continents
  • some continents appear to fit together
17
Q

define plate boundary

A

where two plates meet

18
Q

conservative plates - direction
- features/ hazards

A
  • alongside each other or against each other
  • destructive earthquakes up to 8.5. small earth tremors almost daily
19
Q

divergent - direction
- features/ hazards

A
  • away from each other
  • small earthquakes 5-6 magnitude. not very dangerous volcanoes
20
Q

convergent - direction
- features/ hazards

A
  • towards eachother
  • very destructive earthquakes up to 9.5. very destructive volcanoes. tsunamis can form
21
Q

collision - direction
- features/ hazards

A
  • toward eachother
  • destructive earthquakes 9. landslides. volcanoes are very rare
22
Q

what are destructive plate boundaries

A

it’s another name for convergent plate boundaries

23
Q

compare a convergent and collision plate boundary (4)

A

• both go in the same direction (towards each other)
• both produce extremely destructive earthquakes
• convergent have 1 continental and 1 oceanic but collision have 2 continental
• only convergent can form tsunamis

24
Q

define hotspot and give an example of one

A

where a rising plume of magma breaks through the earth’s surface in the middle of a plate. this causes a volcano. eh hawaiii

25
Q

define volcano

A

an opening or vent in the earth’s surface through which molten material erupts and solidifies as lava

26
Q

where are composite volcanoes found

A

convergent boundaries

27
Q

what are composite volcanoes made of and what is the lava Iike

A

alternating layers of ash and lava

andesitic, thick, sticky lava which doesn’t flow very far before solidifying

28
Q

what are eruptions like for composite volcanoes and why

A

they are explosive due to more silica and more gases

29
Q

what are pyroclastic flows and what kind of volcano are they caused by

A

fast moving current of hot gas and volcanic matter. found at composite volcanoes

30
Q

where are shield volcanoes found

A

divergent plate boundaries

31
Q

what are shield volcanoes made of and what is the lava Iike

A

formed by layers of basaltic runny lava which can flow long distances before solidifying so the volcano is low with gentle sloping slides

32
Q

what are explosions like for shield volcanoes

A

frequent but gentle eruptions produced under low pressure

33
Q

explain the differences between shield and composite volcanoes (4)

A

• shield are formed at divergent boundaries. composite are formed at convergent
• shield are broad, gently sloping. composite are tall and thin
• shield have frequent, gentle eruptions. composite have explosive eruptions
• shield formed from layers of solid lava. composite formed form layers of lava and ash layers

34
Q

two ways that volcanoes can be predicted

A
  • thermal imaging
  • seismometer
35
Q

define earthquake

A

a vibration of the earth’s crust. tectonic plates try to push past each other, pressure is built up which is suddenly released

36
Q

what is magnitude measured with?

A

a seismometer

37
Q

what does it mean that the Richter scale is logarithmic

A

a magnitude of 5.0 is 10 times more powerful than 4.0

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