restless earth Flashcards
state one difference between oceanic and continental crust
- continental crust-granite carries land
* oceanic crust- basaltic carries water
what is meant by the idea of a convection current in relation to plate tectonics?
- Heat rises and falls in the core
- generated by radioactive decay
- this causes the tectonic plates in the mantle to collide or move apart
describe a constructive plate boundary and give an example
- two plates move apart
- causes volcanoes
- eg. Mid Atlantic ridge
describe a destructive plate boundary and give an example
- two plates collide and one plate is subducted beneath the other
- oceanic underneath continental as it is less dense
- causes earthquakes and volcanoes
- eg. andes mountains
describe a conservative plate boundary and give an example
- two plates slide past each other
- causes earthquakes
- eg. San Andreas fault
describe a collision plate boundary and give an example
- two continental plates collide
- causes earthquakes and mountain ranges
- eg. Himalayas
describe the distribution of plate boundaries
- Long lines and bands all over the world
- earthquakes are mainly clustered together with anomalies in the ocean
- less volcanoes than earthquakes on land but more in Ocean
described a shield volcano and give an example
- found on constructive plate boundaries
- formed by eruptions of thin runny lava which flows along way before it solidifies
- Gentle sloping sides and a wide base
- contains basaltic magma - very hot with low silica and gas content
- low explosivity
- eg. Mauna Loa Hawaii
describe a composite volcano and give an example
- found on destructive plate boundaries
- formed by eruptions of viscous sticky lava and ash that don’t flow far
- steep sloping sides and a narrow base
- layers of thick lava and ash
- contains and andesitic magma - less hot but contains lots of silica and gas
- high explosivity
- frequent eruptions
compare two contrasting earthquake hazards
1)Christchurch- 22nd Feb 2011 • magnitude 6.3 • depth of focus 5Km •185 people killed • buildings destroyed
2)Sendai, Japan- 2011 • magnitude 9 •depth of focus 24km • 15,883 deaths •129,225 collapsed buildings
overall Japan more devastating
contrast the primary and secondary impacts of an earthquake hazard
Kashmir Pakistan 2005 Primary- • 780,000 buildings damaged • 3.5 million left homeless •6000 school buildings collapsed
secondary-
• landslides blocked roads and electricity lines
• families left village
compare the primary and secondary impacts (social and economic) of a volcanic event
Chances Peak Monserrat social Impacts- • 23 people died and airport was damaged •Plymouth covered by 1m of ash • extensive damage to peoples homes and transport routes
economic impacts-
• British government gives $4000 for adults and $1700 for children as compensation for losses
•British government promises to send $64 million to replace housing, hospital and airport
explain the ways we can predict for a volcanic event
- Seismometers to detect large numbers of miniature earthquakes
- satellite images to detect the warming of the ground surface
- Chemical sensors to measure increased sulphur levels
Explain how we can plan and prepare for an earthquake
- money to cover the cost
- emergency supply of basic provisions e.g. food and water
- earthquake drills
- transport and good roads for evacuation
- Build earthquake proof buildings
describe a hazard resistant design in a developed country
Japan •damper in roof - reduces building sway •cross bracing - stops floor collapsing •strong steel frames - flexible •shock absorbers •strong double glazed windows - stop glass showering down •deep foundations - prevent collapse
