Geology and the Human Environment.

Eyjafjallajokull (ICELAND)

When and where: 2010 and the south of Iceland.

Cause: Mid-atlantic ridge, which is a divergant plate boundry where new continental plate is being added by the formation of basalt pillows.

Impacts:

• lava deforms land on the side of the volcano.
• glacial melt water cools lavas quickly, causing them to form fragmented highly abrasive particles.
• glacial melt water increases amount of water in rivers and streams, flooding chances increased.
• Europes air travel disrupted over six days.
• animals kept inside to prevent ash entering the food chain.
• contamination of water supply due to ash.

Predication and Management:

• a seismograph is used to see whether the plates are moving.
• many small earthquakes occured in 2009 suggesting plates were active.

Mount Pinatubo (PHILIPPINES)

When and where: 1991 and in the Philippines.

Cause: Philippines plate and Eurasion plate converging, causing the subduction of the Philippines plate, causing andesitic magma to rise and erupt.

Impacts:

• cloud and dust turned day to night.
• earthquakes and heavy rain.
• mudslides caused by typhoons and pyroclastic flow travelling at up to 60km/hr.
• 15000 personal from airbase evacuated.
• 50cm of ash landed on nearby farmland.
• estimated 600000 people lost their jobs.

Prediction and Management:

• assumed to be extinct, but small earthquakes in April/May indicated otherwise.
• predictions allowed for evacuations.

Canterbury (New Zealand)

When and where: 2010 and in Canterbury, southern island of New Zealand.

Causes: A strike-slip fault between the Pacific plate and the Austrailian plate which shows increased pressure and friction over time.

Impacts:

• soil liquifaction.
• sewer systems damaged meaning a contamination of drinking whater.
• damage to historic buildings such as Lyttleton which showed cracks in the church walls.

Prediction and Management:

• earthquake was unknown and not predicted.
• welfare centres were set up where 244 people slept after night of the quake, red cross and salvation army.
• after initial quake large aftershocks were predicted six months later.

Christchurch (New Zealand)

When and where: 2010 and in Christchurch, New Zealand.

Causes:

• aftershock.
• soil liquifaction.
• Alpine fault (thrust fault).
• blind faulting.

Impacts:

• ground displaced.
• subsidence.
• soil liquifaction.
• 160 people killed.
• infrastructure damaged.
• no electricity.

Prediction and Management:

• radar images from orbiting satalites.
• Japanease alos spacecraft which mapped ground deformation.
• aftershock to the previous earthquake.

Staylbridge, Tameside, England

• uses toe weights to reduce the weight of the rock above the road.
• uses metal netting to retain any failing rubble or rock.
• rock bolts used in some places to retain any structures liable to falling due to gravity out weighing friction.

Rock type/structure:

Stronge, hard rock such as igneous or metamorphic rock. Sedimentary rocks such as Limestone are liable to cavaties if water is slightly acidic. Found on syncline not anticline as anticlines are more unstable and can result in slippage of beds under weight and gravity.

Faults/Joints:

Faults or joints as they reduce the stability of the rock allowing water to leak out of the reservoir. Also risk of fault being reactivated by the reservoir.

Permeablilty or Porosity:

Has to be highly impermeable and non pourus so not to allow any water to leak from the reservoir.

Valley:

Water is likely to fall in this area due to the high watertable draining water into the lowest part of the vally.

Rock type/structure:

Hard rock can be used which does not require many additional stability features but does take a long and expensive time to excavate. Whereas soft rock will need support such as metal ribbing and netting and also concrete pillars but will take less time and expense to excavate. Anticlines will reduce the stabililty of the tunnel under gravity increasing likelhood of slippages.

Faults or Joints:

Joints may cause weaknesses in the tunnel as water is able to seep into the tunnel making flooding a risk, but also if a fault were to reactivate then the whole tunnel may be shifted therefore making it useless.

Permeabilty/Porosity:

Should be impermeable to stop any water from getting into the tunnel and causing flooding, rock should also not be porous as this allows the storage of water in the rock which may later lead to flooding also.