Tectonic Landscapes and Hazards

Question 1

what are the two types of the Earths crust

Answer 1

continental and oceanic

Question 2

what is the lisophere

Answer 2

the crust and uppermost mantle which is split into tectonic playes

Question 3

what are convection currents

Answer 3

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

Question 4

how do tectonic plates move

Answer 4

convection currents

Question 5

where are earthquakes/volcanoes most likely to occur

Answer 5

near/on plate boundaries

Question 6

what is a destructive plate boundary

Answer 6

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

Question 7

what is a constructive plate boundary

Answer 7

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

Question 8

what is subduction

Answer 8

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

Question 9

what is a conservative plate boundary

Answer 9

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

Question 10

what causes a destructive/constructive plate boundary

Answer 10

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

Question 11

Where/how is an ocean trench formed

Answer 11

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

Question 12

How/where are fold mountains formed

Answer 12

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

Question 13

How/where are explosive volcanoes formed

Answer 13

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

Question 14

How/where is a new crust formed

Answer 14

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

Question 15

How/where is an ocean ridge formed

Answer 15

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

Question 16

How/where are submarine and island volcanoes formed

Answer 16

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

Question 17

How/where is an rift valley formed

Answer 17

At constructive margin where two continental plates pull apart.

Question 18

Rift valley example: Thingvellir, Iceland

Answer 18

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

Question 19

What is a volcanic hotspot

Answer 19

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

Question 20

how are volcanic hotspots formed

Answer 20

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.

Question 21

What are the types of volcano

Answer 21

shield volcanoes, stratovolcanoes and caldera

Question 22

features of a shield volcano

Answer 22

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

Question 23

how does a shield volcano form

Answer 23

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

Question 24

Features of a stratovolcano

Answer 24

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

Question 25

how are stratovolcanoes formed

Answer 25

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

Question 26

what is a caldera

Answer 26

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

Question 27

how are calderas formed

Answer 27

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

Question 28

how does a lava tube form

Answer 28

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

Question 29

what is a geyser

Answer 29

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

Question 30

Volcanic explosivity index (VEI)

Answer 30

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

Question 31

what is magnitude

Answer 31

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

Question 32

what is the Richter scale

Answer 32

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

Question 33

characteristics of a lava flow

Answer 33

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

Question 34

characteristic of lahars

Answer 34

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

Question 35

characteristics of ash clouds

Answer 35

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

Question 36

characteristics of pyroclastic flows

Answer 36

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

Question 37

the four earthquake hazards

Answer 37

ground shaking, liquefaction, landslides, tsunamis

Question 38

physical factors that increase vulnerability to earthquakes

Answer 38

magnitude, duration, predictability, regularity

Question 39

what is the epicentre

Answer 39

the point on the surface directly above the focus

Question 40

what is the focus

Answer 40

the originating point of an earthquake

Question 41

what are aftershocks

Answer 41

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

Question 42

human factors that increase vulnerability

Answer 42

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

Question 43

what is a seismograph

Answer 43

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

Question 44

monitoring techniques for earthquakes

Answer 44

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

Question 45

Pacific Tsunami Warning System

Answer 45

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

Question 46

monitoring techniques for volcanic eruptions

Answer 46

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

Question 47

Hazard map

Answer 47

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

Question 48

what does hazard mapping allow authorities to do

Answer 48

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

Question 49

emergency planning features

Answer 49

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

Question 50

features of earthquake buildings

Answer 50

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.