Restless Earth

Restless Earth

1. Moving tectonic plates

   • Three layers of the Earth
     • Crust - made from thin layers of tectonic plates
     • Mantle - divided into solid upper part and semi-liquid lower part, which can flow
     • Core - consists of a liquid outer core and a solid inner core
   • Convection currents
     • 1. The core heats up the molten rock which creates convection currents
     • 2. Heated rock rises to the Earth's surface
     • 3. The convection current moves the tectonic plates
     • 4. Molten rock cools and flows back down to the core

2. Plate boundaries, volcanoes and earthquakes

   • Three main plate boundaries
     • Conservative: e.g. San Andreas Fault, California. Two plates slide past each other. Earthquakes
     • Destructive: e.g. Nazca Plate. Two continental plates collide, one plate flows beneath another (subduction). Many earthquakes and volcanoes
     • Constructive: e.g. Eurasian plate. Rising convection currents pull crust apart forming volcanic ridge, e.g. Mid-Atlantic Ridge

3. Volcanic and earthquake hazards

   • Types of volcano
     • Composite: e.g. Pinatubo, Philippines. Found on destructive plate boundaries. Erupts viscous, sticky lava and ash that doesn't flow far. Steep slopes. Narrow base. Layers of thick lava and ash. Less hot andesitic magma with lots of silica and gas. Erupt infrequently but violently, including pyroclastic flows (mix of ash, gases and rock)
     • Shield: e.g. Mauna Loa, Hawaii. Found on constructive plate boundaries & hotspots. Thin, runny far flowing lava. Wide base. gently sloping sides. Hot basaltic magma with low silica and gas. Frequent eruptions but not violent
   • Two contrasting earthquakes, why is there a difference?
     • Kashmir. 2005. 75000 dead. 75000 injured. 2.8 million homeless. $440 million property damage. Remote, mountainous area. LEDC
     • California. 1989. 63 dead. 3757 injured. Up to 12000 homeless. $10 billion property damage. Built up, accessible area. MEDC

4. Managing earthquake and volcanic hazards

   • The difficulties of predicting earthquakes and volcanoes
     • We don't know... when it will happen, exactly where it will happen, how big it will be, what other impacts it may have or how many people live there.
   • What can help us predict earthquakes and volcanoes
     • Look out for... animals and birds moving away from the area, an increase in gas emissions, an increase in soil temperature, the volcano swelling, an increase in small earthquakes or water in ponds getting warmer

5. Earthquake case study: Haiti, 2010

   • Main facts
     • 250000+ homes and 30000 offices and factories destroyed or badly damaged
     • 316000 dead
     • Rubble blocked roads
     • Buildings destroyed including nursing school, midwifery school and the presidential palace
     • Primary impacts
       • People sleeping in streets because of fear
       • Mass graves because there are too many dead people
       • Injured and dead trapped under rubble
       • Phone and power lines down
       • Streets blocked by rubble
   • Relief efforts: 2 years on
     • Only 18% of required homes built.
     • Shortage of clean water
     • 350000 people still living in tents
     • Only 111000 out of 125000 shelters planned had been built
     • Not all promised aid money sent, making recovery difficult
     • 80% of rubble cleared

6. Volcanic eruptions

   • Monsterrat, 1995
     • Whole island was affected
     • Dormant since 17th century
     • 6500+ out of 10000 left the island
     • Sent out large amounts of ash and lava, including pyroclastic flows
     • had a devastating economic and social effect
   • Laki, Iceland, 1783-84
     • The eruption waas huge, occuring in a remote area where people could not escape
     • Poisonous gases caused vegetation and subsequently animals to die, leading to the death through starvation of over 25% of Iceland's population.
     • No aid from other countries was possible
     • A huge dust cloud covered much of Europe and led to poor summers for years afterwards