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Physical Geography > [Unit 1: Enquiry Question 1] > Flashcards

[Unit 1: Enquiry Question 1] Flashcards

Tectonics

1
Q

Constructive (divergent) boundary

A

A plate boundary where two plates move away from each other. Plates move by sea floor spreading. magma rises from mantle creating new crust which pushes the plates further apart.

DRC on boundary, mt nyiragongo

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2
Q

Collision plate boundary

A

A plate boundary where two (continental & continental) plates move toward each other, neither can subduct. so they both crumple and form mountains (e.g. Himalayas)

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3
Q

destructive boundary

A

A plate boundary where two (oceanic & continental OR oceanic & oceanic) plates move toward each other, the more dense one subducts. Moves via slab pull

cause deep ocean trench, fold mountains, earthquakes (tsunamis).

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4
Q

Conservative boundary

A

Where two tectonic plates slide past each other, but where crust is neither formed or destroyed. earthquakes form from the friction build up (e.g. San Andres Fault)

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5
Q

Intra-plate earthquakes

A

These occur in the middle or interior of tectonic plates and are much rarer than boundary earthquakes. ancient fault lines are reactivated forming seismic waves. Some may form new plate boundaries. weakened crust cracks under pressure

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6
Q

Intra-plate volcanoes

A

formed at hotspots, this is fed by a mantle plume which is an area with really hot and low density magma. This breaks through the crust and forms a volcano

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7
Q

Slab Pull

A

the pulling of a tectonic plate as its edge subducts deep into the mantle. denser oceanic plates subduct at cold downwellings. This causes cooler mantle areas. affecting convection

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8
Q

Oceanic Crust

A

7km deep. 28-400°C. low. Basalt. Solid

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9
Q

Continental crust

A

70km thick. 28-400°C. low. Granite. Solid.

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10
Q

Mantle

A

700-2890km thick. 870°C. medium. Peridotite. Solid & liquid layers

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11
Q

Outer Core

A

2890-5150km thick. 4400-6100°C. dense. Iron (mainly) and sulphur. Liquid generating magnetic field.

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12
Q

Inner Core

A

5150km-centre. 7000°C (radioactive decay). very dense. Iron (mainly) & nickel. Solid

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13
Q

Structure of the Earth (Chemical & Physical layers)

A

Oceanic crust (basalt)
Continental crust (granite)
Mantle (Peridotite)

Lithosphere - crust + upper mantle
Asthenosphere - upper mantle
mesosphere - (lower) mantle

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14
Q

How do plates move (divergent boundary)?

A

divergent plate boundaries - the crust thins as it is pulled apart, mantle rises to fill gap. This creates new seafloor. This new seafloor pushes the plates apart on either side.

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15
Q

How do plates move (destructive boundary)?

A

the less dense plate subducts into the mantle.
the older/cooler rock pulls the plate into the mantle behind it
(slab pull)

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16
Q

what discovery was made for tectonics in 1915

A

Alfred Wegner - theory of continental drift.
-fossils oceans apart (same green plants) on all continents (once all had same climate)
-mountain ranges have similar rock types. Pangea lines them up as one big mountain range
-What causes continents to move? Scientists mocked it.

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17
Q

what discovery was made for tectonics in 1918

A

Sonar tech developed.

Map ocean floor (thought it was flat at first)

They were now aware of crust under ocean (ocean floor move)

Belief isn’t credible but gaining support

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18
Q

what discovery was made for tectonics in 1919

A

Arthur Holmes - suggests convection currents in mantle

-upwards ruptures surface

-downwards causes buoyant continents to crumple into mountains

-lateral moves surface like conveyor belt

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19
Q

what discovery was made for tectonics in 1946

A

Ocean floor mapped completely.

-mid oceanic ridge

-mountains

-volcanoes

-deep ocean trenches

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20
Q

what discovery was made for tectonics in 1954

A

J.P.Ruthé - Map of volcanic eruptions & earthquake zones

21
Q

what discovery was made for tectonics in 1960

A

Harry Hess & Robert Dietz - sea floor spreading theory

22
Q

what discovery was made for tectonics in 1963

A

pattern of magnetic striped rock. Provides evidence for seafloor spread theory.

23
Q

what discovery was made for tectonics in 1965

A

J.Tunzo Wilson - plate tectonics theory

24
Q

what discovery was made for tectonics in 1983

A

GPS available for public use to track movement of Earth’s surface.

25
Q

define Earthquake

A

caused by a sudden movement near to surface along a fault

26
Q

define the Benioff Zone

A

Area of seismicity corresponding with the slab being thrust downwards in a subduction zone. cause multiple earthquake at once

27
Q

Two types of seismic waves

A

body waves and surface waves

28
Q

Two types of body waves

A

P waves and S waves

29
Q

Features of P waves

A
  • Longitudinal
  • Travel through solids and liquids
  • Travel faster than S-waves

-first waves to come

-compress and expand the ground

-cause buildings to expand and contract

30
Q

Features of S waves

A

after P waves

vibrate side to side and up and down

shake ground back and forth

shake buildings

cant move through liquids

slower than P-Waves

31
Q

What are the two types of surface waves

A

Love waves and Rayleigh waves

32
Q

features of surface waves

A

slower
more violent

Rayleigh:
make the ground roll like ocean waves

Love:
shake from side to side

33
Q

What is primary hazard (and examples)

A

immediately, direct result of the earthquake

e.g crustal fracture and ground shaking

34
Q

What is secondary hazard (and examples)

A

as a consequence of ground shaking

e.g. land slides, soil liquification and tsunamis

35
Q

2011 Tohoku tsunami case study

list as many facts as you can

A

18500 deaths
$220 billion damages

caused by magnitude 9 earthquake (focus of 24.4km)
-pacific plate subducting under Okhotsk plate
wave height was 3-40m high hitting at 35km/hr

hit Japans low lying east
surrounded by deep waters
-allowing waves to retain energy as they travelled
estuaries funnelled the waves

4.4million left without electricity
7 reactors at fukushima meltdown
transport lines damaged

36
Q

what is soil liquification

A

When loosely packed grains of soil held together by friction get shaken by the earthquake, the soil becomes destabilized, increasing the space between grains. Soil flows like liquid.

Causes buildings to tip/sink/collapse

37
Q

What determines the impact of a tsunami

A

-duration
-wave amplitude
-physical geography of the coast
-coastal ecosystem buffer
-timing
-coastal development & proximity from coast

38
Q

what is a volcano

A

extrusive structure found on Earth’s surface ranging from gentle fissure eruptions to explosive composite cones.

39
Q

The shape of a volcano is related to its type of lava.

What are the 3 main types of lava?

A

-basaltic
-andesitic
-rhyolitic

40
Q

give the eruption temp, gas content, viscosity and SiO2 content of all three types of lava

A

Temp, Gas, Viscosity, SiO2
basaltic: high, low, low, 50%
andesitic: mid, mid, mid, 60%
rhyolitic: low, high, high, 70%

41
Q

Explosivity depends on: temp, gas, viscosity and SiO2 content.

how do each of these impact the explosiveness?

A

higher temp increases explosion

higher gas content increases explosion

lower viscosity increases explosion

lower SiO2 increases explosion

42
Q

what are pyroclasts

A

in all explosive eruptions
hot fragments projected
damage on impact

43
Q

what is tephra

A

all explosive eruptions

collective term: airborne or ground-flowing pyroclasts

major destruction over distances

44
Q

what are landslides

A

disturbing of land by magmatic pressure

flows of rocks, mud and tephra

destruction of property and land

45
Q

what are poisonous gases

A

any eruption

gases (HCl, CO2, HF, SO2)

Toxic (1700 in Cameroon (1986) died of asphyxiation)

46
Q

what are lahars

A

volcanic mudflow

depends on slope and volume

triggered by rainfall

47
Q

example of a lahar

A

columbia:
-Armero was buried by lahar in 1985.
-6 major valleys
-travelled at 60kmhr
-50m deep
-killed 23000
-buildings swept away and buried

48
Q

What is a jokulhlaup

A

glacial outburst flood

causes erosion and deposition

large volumes of water

caused by failure of ice dam

49
Q

example of jokulhlaup

A

Iceland

EFJ erupted in 2010, roads damaged, bridges and house washed away towns evacuated.
was anticipated though.

Physical Geography (4 decks)

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