Tectonics Flashcards
What are the properties of continental plates?
Thicker plate (30-50km)
Less dense than oceanic plates
Made of granite
What are the properties of oceanic plates?
Thinner plates (6-8km)
Denser than continental plates
Made of basalt
Describe what occurs at a convergent plate boundary (oceanic-continental)
Plates move together
Oceanic subducts and sediment melts
CO2 and magma is formed, force through cracks and builds pressure
Explosive composite volcano formed
Describe what occurs at a convergent plate boundary (continental-continental)
Plates move together Same density plates so no sinking Both plates crumble and form mountains Severe earthquakes, no volcanoes Himalayas are an example
Describe what occurs at a convergent plate boundary (oceanic-oceanic)
Plates move together
Earthquakes occur and volcanoes formed
Magma forces way through crack and make volcanic islands
Iceland is an example
Describe what occurs at a divergent plate boundary (oceanic-continental)
Plates move apart
If lots of magma escapes then volcano forms
No earthquakes
The middle is an oceanic ridge
Describe what occurs at a conservative plate boundary (oceanic-continental)
Plates slide past eachother They get stuck Pressure builds up When they release, there is a big earthquake San Andreas is an example
What is the difference between the Mercalli scale and the Richter scale?
Mercalli- numbered 1-12 in roman numerals, measures the damage and how many people could feel it
Richter- numbered 1-9, measures how powerful each quake is, each level is 5X more powerful than the last
What is an epicentre?
The point on the surface where there is the worst damage
What is the focus?
Where the actual earthquake starts, usually underground
What are the pros of living by a volcano and an earthquake zone?
Volcano -Land is cheaper from the danger -Land if fertile from lava -Volcanoes attract tourists Earthquakes -Land is cheaper from danger -Not obvious to see that it is dangerous, people cant afford to move away
What is a case study example for an LIC volcanic eruption and some key facts and figures?
- Montserrat, Sufriere Hill
- Atlantic plate and Caribbean plate
- 1995 and 1997
- 1km squared of coral reef ruined
- Pyroclastic flows move at 100mph
- 43 deaths
- 11,000 people lived there but had to migrate north in 1996
- 5,000 people fled
What is a case study example for an LIC earthquake and some key facts and figures?
- Kashmir, South Asia
- 8th Oct 2005
- Magnitude was 7.6, lasted 37 seconds
- 79,000 deaths
- $5 billion came from other countries to help
- Broken sewers, landslides, entire villages wiped out, cost to rebuild buildings and roads
What is a case study example for an HIC earthquake and some key facts and figures?
- San Francicso, California
- 17th Oct 1989
- Magnitude was 6.9, lasted 15 seconds
- 9 deaths
- Bay bridge upper deck collapsed, Cyprus freeway had 1 and a half of collapsed road, lots of gas pipes triggered fires
How do people predict earthquakes?
Seismologists predict 6-10s as they cause damage but not everyone as there are around 35,000 a year. Gas from burning uranium is found in rocks and there are changes in electromagnetic fields. More success predicting aftershocks.
How do people protect themselves from earthquakes?
They secure objects inside houses with velcro, floating buildings absorb energy and some buildings electronically sway the opposite way to the ground.
How do people prepare for earthquakes?
There is an earthquake preparedness day in the USA, learning centres and simulations help people experience earthquakes and smoke chambers to help people practise escape- they do lots in Japan.
What is a HIC case study for predicting volcanoes and some key facts and figures?
- Mount St Helens
- Lots of signs of eruptions, earthquakes, landslides, animal behaviour etc
- Reduced car speed to 15mph, stopped airports, told people to stay inside, had $1 million ready
- Was a growth in tourism and fertile land but crops were ruined and unemployment increased
What is a LIC case study for predicting volcanoes and some key facts and figures?
- Nyirogongo
- Lots of signs of eruptions, tremors, plumes of ash and rock
- Not much was done because there was little communication and money
- 120,000 people left homeless
- 80% of local infrastructure damaged
- HIC countries gave lots of food and medicine but not money as government might not spend it wisely
