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Geography > Tectonic Landscapes and Hazards > Flashcards

Tectonic Landscapes and Hazards Flashcards

1
Q

what are the two types of the Earths crust

A

continental and oceanic

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2
Q

what is the lisophere

A

the crust and uppermost mantle which is split into tectonic playes

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3
Q

what are convection currents

A

the movement of magma below the crust. Hot magma rises cools and sink back down creating circular currents

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4
Q

how do tectonic plates move

A

convection currents

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5
Q

where are earthquakes/volcanoes most likely to occur

A

near/on plate boundaries

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6
Q

what is a destructive plate boundary

A

a plate boundary where oceanic and continental plates move towards each other (converge)

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7
Q

what is a constructive plate boundary

A

a plate boundary where a continental and oceanic plate move away from each other (diverge)

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8
Q

what is subduction

A

the process in which a plate is subducted under another plate at a destructive boundary. The denser oceanic plate is pushed under the continental plate. subducting plate melts in mantle

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9
Q

what is a conservative plate boundary

A

a plate boundary where two plate move against eachother in opposite directions

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10
Q

what causes a destructive/constructive plate boundary

A

dependent on the way the convection current travels below. If two circles go towards then destructive, if two flow away from each other then constructive

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11
Q

Where/how is an ocean trench formed

A

where subduction takes place at destructive boundary. e.g. Marina trench

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12
Q

How/where are fold mountains formed

A

at destructive plate boundary. The continental plate is crushed and folded upwards. e.g. Andes Mountains

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13
Q

How/where are explosive volcanoes formed

A

at destructive margin as oceanic plate sinks it melts and molten magma rises to surface. e.g. Mount Merapi

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14
Q

How/where is a new crust formed

A

At constructive plate boundary where two oceanic plates move apart and space created between the two fills with magma. e.g. Mid-Atlantic

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15
Q

How/where is an ocean ridge formed

A

At constructive margin when lava cools forming a ridge in the ocean. e.g. Mid-Atlantic ridge

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16
Q

How/where are submarine and island volcanoes formed

A

At constructive plate boundary when submarine volcanoes sometimes rise to the surface. e.g. Surtsey, Iceland

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17
Q

How/where is an rift valley formed

A

At constructive margin where two continental plates pull apart.

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18
Q

Rift valley example: Thingvellir, Iceland

A

Iceland slowly being torn apart as North American and Eurasian plate diverges.

  • Rift valley 7.7km wide
  • average 7mm wider a year
  • valley floor subsiding by average of 1mm a year
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19
Q

What is a volcanic hotspot

A

area in the middle of a plate w/ unusual amount of volcanic activity

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20
Q

how are volcanic hotspots formed

A

intense radioactivity in core causes massive plume of magma which melts and pushed through crust. Plume then lies at fixed position, as plate moves over new hotspot, upwelling magma creates a line of volcanoes.

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21
Q

What are the types of volcano

A

shield volcanoes, stratovolcanoes and caldera

22
Q

features of a shield volcano

A

constructive boundaries and hotspots; circular shape with gently sloping sides; composition of lave with no layers; runny lava; regular eruptions

23
Q

how does a shield volcano form

A

basaltic magma w/ high temp gets to surface via cracks in crust. magma makes fluid lava which travels far before cooling creating gentle slopes.

24
Q

Features of a stratovolcano

A

destructive plate boundary; conical shape w/ steep sides; alternate layers (strata) of ash and lava. explosive eruptions

25
Q

how are stratovolcanoes formed

A

acidic lava w/ high viscosity that cools quick, doesn’t flow far before solidifying making steep sides. explosive eruptions of ash and lava bombs

26
Q

what is a caldera

A

large scale volcanic crater that can be up to several km in diameter

27
Q

how are calderas formed

A

either by magma chamber emptying causing roof to collapse; or massive explosive eruption

28
Q

how does a lava tube form

A

forms beneath surface when low viscosity develops a hard crust through which lava flows

29
Q

what is a geyser

A

a vent in crust that ejects hot water and steam. it erupts when super heated groundwater confined at depth becomes hot enough to blast to surface

30
Q

Volcanic explosivity index (VEI)

A

measure of the explosiveness of a volcanic, measures how much is ejected, how high material is thrown up and how long eruption lasts. Logarithmic scale 1-8

31
Q

what is magnitude

A

a quantitative measure of the size of an earth quake using Richter scale

32
Q

what is the Richter scale

A

a measure of the magnitude of an earthquake. uses logarithmic, each level is ten times stronger from 1 to 10

33
Q

characteristics of a lava flow

A

molten rock flowing down volcano, lava from shield goes further. local effect may travel few km endangering close villages/towns

34
Q

characteristic of lahars

A

volcanic mudflows of ash and water form rain melted snow etc. travels at great speed down mountain. local effect travels several km endangering close villages/towns

35
Q

characteristics of ash clouds

A

ash thrown into atmosphere, blocks sun. settles on everything eg. crops and buildings. Large effect, may reach 10-15 km high and spread over thousands of km

36
Q

characteristics of pyroclastic flows

A

burning clouds of gas and ash w/ temps up to 1000°c travelling up to 200km/h. local effect, travel several km

37
Q

the four earthquake hazards

A

ground shaking, liquefaction, landslides, tsunamis

38
Q

physical factors that increase vulnerability to earthquakes

A

magnitude, duration, predictability, regularity

39
Q

what is the epicentre

A

the point on the surface directly above the focus

40
Q

what is the focus

A

the originating point of an earthquake

41
Q

what are aftershocks

A

ground tremors occurring after a major earthquake but from same focus.

42
Q

human factors that increase vulnerability

A

wealth, education, governments, age, health, population density, time of day, emergency services

43
Q

what is a seismograph

A

a device used to detect vibration in earths crust. an increase may indicate an oncoming earthquake

44
Q

monitoring techniques for earthquakes

A

laser beams - detects plate movement
levels of radon gas, increase indicates earthquake
seismograph

45
Q

Pacific Tsunami Warning System

A

uses a network of seismographs and ocean buoys to detect earthquakes that can cause tsunamis. warning given to local centres who warn people

46
Q

monitoring techniques for volcanic eruptions

A

remote sensing - satellites monitoring gas emissions w/ thermal imaging
visual signs, seismographs, tiltmeters - monitor shape of volcano
GPS

47
Q

Hazard map

A

a map highlighting areas most affected by volcanoes, earthquakes and tsunamis

48
Q

what does hazard mapping allow authorities to do

A

limit access to hazardous areas, control development in areas at risk

49
Q

emergency planning features

A

education, divert lava flows, emergency services trained and have correct resources, exclusion zone, emergency kits, infrastructure designed to withstand disasters

50
Q

features of earthquake buildings

A

steel frame, rolling weights on roof, cross bracing to support frame, open areas for evacuees, shock absorbers in foundation, deep foundation sin solid rock, roof covering area immediately outside building.

Geography (6 decks)

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