G1 - Question 2 - Rivers and tectonics - Part 1 - Tectonics

Question 1

What are the four layers of earth?

Answer 1

Lithosphere
Mantle (Aesthenosphere and Mesosphere) 2900km thick
Outer core
Inner core

Question 2

What are the two types of crust on the lithosphere?

Answer 2

Oceanic (7-10km thick, denser than Cont, basaltic)

Continental (10-35km thick, granitic)

Question 3

What drives plates to move across the face of the earth?

Answer 3

Convection currents?

Question 4

Name four types of plate margin with examples

Answer 4

Destructive (Nazca-South America)
Constructive (Mid Atlantic Ridge)
Conservative (San Andreas fault)
Collision (Himalayas)

Question 5

What is a hotspot

Answer 5

a weak part of the crust where magma is capable of breaking through to form a shield volcano, such as Hawaii. Technically intra plate volcanism, and basaltic flows

Question 6

Montserrat: Briefly outline causes and consequences of the Soufrieres eruption of 1997

Answer 6

Causes:
As an island arc formed by subduction, eruption was inevitable. The subduction of the North American Plate beneath the Caribbean plate led to the rise of magmatic material. This led to pryoclastic flows, an ash cloud of 40,000ft and highly viscous lava at 800DegC
Consequences
Plymouth (capital) evacuated, 6000 evac., 19 killed, govt buildings lost, seven villages destroyed, 175 homes destroyed, Tephra damaged 80% of buildings, silicosis threat

Question 7

Secondary impacts of Montserrat’s eruption

Answer 7

11,000 permanently migrated, psychological problems amongst victims, hospitals temporary incapacitated, traffic congestion, unemployment from 7-50%, tourism collapsed, long term ecosystem damage.

Question 8

Causes: Mt St Helens

Answer 8

Destructive boundary - Juan De Rico subduction beneath the Northern Plate. several smaller earthquakes of 3.3-3.6M on richter. 5.1M Quake led to collapse of north face, causing lateral blast of 19 miles (pyroclastic flow), alongside 16 mile high plume

Question 9

Impacts: Mt St Helens

Answer 9

57 deaths, 15 million trees destroyed (large carbon sink and storage), $1.1 billion property and business damage; loss of huge area of ecosystem

Question 10

Management Strategies for volcanoes (7)

Answer 10

Volcanocams
Gas Analysis (sulpher)
Seismic Studies
Boreholes
Ground deformation studies
Gravity Surveys
Hydrological Surveys (test temp and contam)

Question 11

Name a i. Less Viscous Magma

ii. A destructive magma

Answer 11

i. Rhyolite, andesitic

ii. Acidic

Question 12

What is a batholith?

Answer 12

large emplacement of igneous rock commonly at margins

Question 13

What is an ocean trench (and example?)

Answer 13

A deep topographic depression near subduction zones, such as the Mariana Trench

Question 14

Eyjafjalljokull: causes

Answer 14

Magma rise into the volcanic chamber due to the movement of the mid atlantic ridge. Eventual explosion was a VEI of 2-4

Question 15

Eyjafjalljokull: Consequences

Answer 15

Consequences:
63,000 flights cancelled in 23 countries
20% of African exports went into rot.
European airspace closure cost £6mill/day
Animals threatened by fluoride poisoning
Volcanic tourism rose by 64%

Question 16

Loma Preita 1989: Causes and consequences

Answer 16

slip-strike of the pacific and north american plate, causing a 6.9 M earthquake.
63 killed, 12,000 displaced, major damage in San Fransisco Bay due to amplification of the soft geology - unconsolidated sediment - infrastructure damage- viaducts and minitiz bridge

Question 17

List techniques to mitigate earthquake damage

Answer 17

Base Isolators in buildings - LA City Hall
Hydraulic Decompressors
Retrofitted steel jackets on bridges (San Fransisco Bay Bridge)
Earthquake Days - Tokyo
Education and guidance booklets
Triangular shape with deformation zones (Trans-America building)

Question 18

Causes of the Asian Tsunami

Answer 18

Rupturing of the Sundra and Indian plates at the trench near the subduction zone caused a megathrust of water due to a 9.0M Quake - jolt of the Indian plate some 5m - wave height 5-40m

Question 19

How many casualties were there from the Asian Tsunami?

Answer 19

294,000 immediate

Question 20

Why was the Asian Tsunami so destructive?

Answer 20

Sumatra was a low lying island with no defences or warning systems. The wave could travel far up the island quickly. 70% of industries were located on the coast in predominantly agriculture. People went towards the sea as the water retreated prior to the wave

Question 21

Haiti Earthquake: Causes

Answer 21

Conservative boundary - movement of the ~Enriquillo plate-platain garden fault. 25km from Port Au Prince - a dextral fault, which emitted a 7M quake

Question 22

Consequences of Haiti

Answer 22

Leogane - 90% property destroyed
UN HQ and governmental bodies destroyed
222,000 killed immediately, 3.5 million impacted
Thousands more died in aftershocks due to building damage
75,000 buried in mass graves
People reliant on NGO and international aid
Most live in temporary accommodation as recovery continues - suffered from a cholera epidemic - 8,000 killed

Question 23

Causes of 2011 Japanese Tsunami

Answer 23

Megathrust Tsunami caused by the tectonic stress from the subduction of the Pacific plate beneath Honshu - 9.0M

Question 24

Consequences: 2011 Japanese Tsunami

Answer 24

1.5 million without water
15,000 deaths
Nuclear irradiation from the Fukushima Nuclear Plant
$34.6 billion damage

Question 25

Details of three gorges dam

Answer 25

$38 billion
13 cities, 1600 villages submerged
1.3million people displaced
11 times more power than the Hoover dam
Supplies fresh water to north china, where only 15% freshwater is available