G1 - Question 2 - Rivers and tectonics - Part 1 - Tectonics Flashcards
What are the four layers of earth?
Lithosphere
Mantle (Aesthenosphere and Mesosphere) 2900km thick
Outer core
Inner core
What are the two types of crust on the lithosphere?
Oceanic (7-10km thick, denser than Cont, basaltic)
Continental (10-35km thick, granitic)
What drives plates to move across the face of the earth?
Convection currents?
Name four types of plate margin with examples
Destructive (Nazca-South America)
Constructive (Mid Atlantic Ridge)
Conservative (San Andreas fault)
Collision (Himalayas)
What is a hotspot
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
Montserrat: Briefly outline causes and consequences of the Soufrieres eruption of 1997
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
Secondary impacts of Montserrat’s eruption
11,000 permanently migrated, psychological problems amongst victims, hospitals temporary incapacitated, traffic congestion, unemployment from 7-50%, tourism collapsed, long term ecosystem damage.
Causes: Mt St Helens
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
Impacts: Mt St Helens
57 deaths, 15 million trees destroyed (large carbon sink and storage), $1.1 billion property and business damage; loss of huge area of ecosystem
Management Strategies for volcanoes (7)
Volcanocams Gas Analysis (sulpher) Seismic Studies Boreholes Ground deformation studies Gravity Surveys Hydrological Surveys (test temp and contam)
Name a i. Less Viscous Magma
ii. A destructive magma
i. Rhyolite, andesitic
ii. Acidic
What is a batholith?
large emplacement of igneous rock commonly at margins
What is an ocean trench (and example?)
A deep topographic depression near subduction zones, such as the Mariana Trench
Eyjafjalljokull: causes
Magma rise into the volcanic chamber due to the movement of the mid atlantic ridge. Eventual explosion was a VEI of 2-4
Eyjafjalljokull: Consequences
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%
Loma Preita 1989: Causes and consequences
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
List techniques to mitigate earthquake damage
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)
Causes of the Asian Tsunami
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
How many casualties were there from the Asian Tsunami?
294,000 immediate
Why was the Asian Tsunami so destructive?
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
Haiti Earthquake: Causes
Conservative boundary - movement of the ~Enriquillo plate-platain garden fault. 25km from Port Au Prince - a dextral fault, which emitted a 7M quake
Consequences of Haiti
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
Causes of 2011 Japanese Tsunami
Megathrust Tsunami caused by the tectonic stress from the subduction of the Pacific plate beneath Honshu - 9.0M
Consequences: 2011 Japanese Tsunami
1.5 million without water
15,000 deaths
Nuclear irradiation from the Fukushima Nuclear Plant
$34.6 billion damage
Details of three gorges dam
$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
