Slides in this set
The Ring of Fire, basin of Pacific Ocean: Example
of place where there are lots of volcanoes
around the pacific ocean. 90% worlds volcanoes
occur here as is margin of many destructive,
2.) Peru-Chile trench, South America: Example of an ocean trench.
An ocean trench such as the Peru-Chile trench is a deep depression in
the ocean floor which is formed at a subduction zone. Here the denser
oceanic Nazca plate is being subducted (pushed under) the less dense
continental South American plate to create the Peru-Chile trench.
3.)Mount St Helens, Washington State, USA: Example of destructive plate boundary &
· Convection currents in mantle due to hot spots on outer core cause Juan de Fuca
(oceanic) and North America (continental) to converge
· Denser oceanic Juan de Fuca subducted under continental N.A
· As Juan de Fuca descends into mantle melts due to friction and intense temperature.
· Lighter so pushed through continental NA crust through fissures to collect in magma
· Pressure builds up and explosive volcanic eruption may occur.…read more
Mid Atlantic Ridge, Iceland owes existence to: Example of constructive plate margin and ridge
of undersea mountains.
· Convection currents diverging move N.A and Eurasian
plates apart at rate of 4cm per year.
· Leave cracks and fissures allowing magma from the
mantle to escape rising to fill the gaps eventually
erupting through shield volcano as less viscous basic
lava, onto the surfaces and cooling as new land.
· Process can create huge ridges of undersea mountains
and volcanoes such as the Mid-Atlantic Ridge
· Iceland owes existence to ridge.
San Andreas Fault, California: Example of conservative margin
· 2 plates move sideways past each other, or in same
direction at different speeds
· As grind past each other stress released as seismic waves
· At San Andreas Fault, NA plate is moving slower NW by an
average of 1cm per year relative to the Pacific plate, which
is moving NW by an average of 6cm per year.…read more
How are shield and composite volcanoes different?
Shield E.g. Iceland Composite E.g. Mt St Helens
· `Shield like' profile · Steep sided with a distinctive cone shaped
· Gentle slopes and wide base (due to runny profile
lava cooling and solidifying far away) · High with a narrow base
· Frequent eruptions of basic lava · Spews out viscous silica rich, acid lava that
· This less viscous basic lava flows at high flows short distances before cooling
speeds and long distances before cooling forming the steep slopes
giving the characteristic shield profile · Eruptions are infrequent and explosive of
lava and ash
· Layers of alternating ash and lava build up
from successive eruptions
· Secondary or parasitic cones formed when
the main vent gets blocked…read more
Peruvian Andes, South America: Challenges of living in a fold mountain area and uses.
Run length of West Coast of South America
7000km cover 6 countries
Formed as a result of convergence of Nazca and South American plate at destructive boundary
x Harsh physical geography Higher mountain slopes used to graze animals instead of grow
x Steep relief, average 400m high makes farming difficult crops. Steep slope terraced to help retain water and make
x High altitude makes breathing difficult growing crops easier
x Mountainous terrain means isolates, makes communication Tunnels built through some fold mountains to make straight fast
difficult as hard to construct roads and railways roads improving communication
Zigzag paths carved in side of some mountains to reach mines.
Llamas who can sustain 25% bodyweight used to carry materials
· Subsistence food for personal consumption
· Terraces `steps' in mountains create flat land to Hydro Electric Power (HEP):
overcome steep relief, also retain water, limit movement · Steep slope and narrow valleys make ideal for HEP. Steep relief
already thin soils increases water velocities.
· Crops mainly grown in the lower valleys and include · A micro hydro has been built in La Peca that currently powers
soya, rice and cotton however the staple is potato. electricity at night, which is having a huge positive impact on the
· Llamas have (capacity to carry >25% of their body inhabitants including within education.
· Inca Trail, Machu Picchu which is South America's best-known track is
UNSECO ((one of only 23)world heritage site
· Andean countries rank top ten for tin, nickel silver and
· Inca trail covers 50km of old pathways linking together the old Inca
settlements in the inhospitable mountains. Strictly controlled and only 200
· More than half of Peru's exports are in mining.
trekkers and 300 guides allowed to start out each day.
· The Yanacocha gold mine in Peru is the largest in the
· Tourists pay $50 each.
· $40 mil to Peruvian govt.
· The nearby town of Cajamarca has grown from 30,000
· Issues: Erosion, Hotels owned by TNC's (Orient express), high paying jobs
when the mine started to 240,000 people in 2005.
taken by foreigners, litter, cultural leakage…read more
Yellowstone National Park, Seattle: Supervolcano
Large eruption VEI 8, 1000 x Mt. St Helens
Emit more than 1,000km3 of material
Caldera (depression) rather than conical
Magma chamber beneath Yellowstone is believed to be 80km x40km x8km
Hydrothermal features like Geyser Old Faithful
Infrequent last eruption 630,000 y.a
Destroy 10,000km2 of land killing 87000 people.
1 in 3 people affected by the eruption would die.
Ash cloud circle globe reaching UK within 5 days
Ash cloud block sunlight cooling by ~21oc
Famine, 75% crops die…read more
Indian Ocean Tsunami 26th December 2004: Tsunami causes, effects, responses)
Causes: Secondary effect of a 9.1-9.3 magnitude earthquake that was a result of the Indo-Australian plate subducted
beneath the Eurasian plate. At the epicentre of the quake, on the coast of Sumatra the energy released by the 20m upward
thrust of the seafloor displaced billions of tonnes of seawater sending a series of progressive waves to propagate over the
12 countries directly effected, most countries bordering Indian ocean e.g. Sri Lanka, Maldives, Thailand
No early warning system in Indian Ocean
In total >220,000 (identification of dead on large scale issue) died and 650,00 seriously injured, 2 mil homeless
Aceh province of Sumatra most badly hit closest to the epicentre, 1500 settlements wiped out,
Every 1.5m of coastline was exposed to 1000tons of water
¾ of the tsunamis victims died in Sumatra
Beach resorts on Phi Phi Island, Thailand, decimated
Sri Lanka was badly hit, with villages & tourist resorts flooded on coast
High population density and tropical climate means diseases are transmitted fast epidemic feared with diseases such as Cholera, Dysentery and
Hepatitis easily transmitted, especially with rotting corpses
1.7 million people were displaced
Coastal ecosystems such as mangroves, coral reefs and forests destroyed by wave surge
Many more ecosystems polluted by human and chemical waste in the floodwater
Short term Long term
Action Aid raised £13million and immediately sent food Action Aid offered Psychological counseling
aid £372 million raised by British public +1 year to rebuild
Fresh water, purification tablets, food. An early warning system for Tsunami in the Indian
100 million public donations from UK. Ocean established in June 2006, through co-operation
from many governments…read more