Restless Earth Flashcards
What is the Asthenosphere?
The sticky, dense layer of rock in the mantle
What is the Lithosphere?
The crust and the solid top layer of the mantle
What is the core made of?
Iron and Nickel
Describe the differences between Oceanic crust and Continental crust.
Oceanic - made of Basalt, underneath water
Continental - made of Granite, underneath land
Describe the differences between Granitic rock and Basaltic rock.
Granite - large crystals, formed by magma cooling slowly, orange-brown colour, makes continental crust
Basalt - no visible crystals, occurs in lava flows and sheets, black-grey colour, makes oceanic crust
Explain how tectonic plates move.
Earth core gives off heat causing convection currents or movement of magma in the Asthenosphere causing the crust sitting on top of it to move and the tectonic plates move too.
Outline the key features of the Earths structure.
Core - inner core (solid), outer core (liquid)
Mantle - above core, low density, upper solid, lower liquid
Crust - solid, low density, tectonic plates - oceanic (more dense, basaltic rock, below water) continental (less dense,thick, granitic rock, below land)
Name all 12 tectonic plates.
Pacific, Antarctic, Philippines, Indo-Australian, North-American, Nazca, South-American, Caribbean, African, Eurasian, Iranian, Arabian
Name the 4 types of plate boundaries.
Constructive - Plates pull away from each other
Destructive - Plate pushes under other
Collision - Plates push into each other
Conservative - Plates slide past each other
Explain what happens at a Constructive plate boundary.
Convection currents cause oceanic plates move away from each other
Basaltic material and hot magma rises through gap
Mid ocean mountain range formed
Magma continues to rise to form a volcanic island
Explain what happens at a Destructive plate boundary.
Convection currents move plates
Oceanic plate subducts under less dense continental plate
Forms a fold mountain and ocean trench
Magma rises through weaknesses forming volcanoes
Explain what happens at a Collision plate boundary.
Convection currents cause two continental plates to move towards each other
Same density so no subduction
Crust buckles to form fold mountains
Explain what happens at a Conservative plate boundary.
Convection currents cause plates to slide past each other
No subduction or magma therefore crust neither created or destroyed Stress builds up in crustal rocks from friction which causes earthquakes when released
Define an earthquake.
The shaking of the Earth’s crust caused by rock movement.
Define a volcano.
A cone shaped hill or mountain formed by the lava and ash from eruptions.
Describe the 3 types of volcanoes.
Extinct - not erupted for 1000 years, shape worn away by wind and rain
Dormant (sleeping) - not erupted for years or even centuries but still seeps gas sometimes
Active - erupted recently and likely to erupt again
What is the hot spot theory?
When hot magma rises to the surface pushing through a continental plate crossing over it, forming chains of volcanoes over thousands of years.
Describe the features of a shield volcano.
Mainly formed by basaltic magma, Low, wide cone, large, gentle slope (lava drizzles/slides down)
Describe the features of a composite volcano.
Made of andesitic lavas, steep sided, bumpy cone, layers of lava and ash.
What are pyroclastics?
Pieces of ash and rock debris or material destroyed in explosive eruptions.
Describe the features of basaltic magma.
High temp, low silica/gas, fluid lava flow, little explosive activity, found in shield volcanoes on conservative plate margins
Describe the features of andesitic magma
Low temp, more silica than basaltic, dissolves gases, less fluid, more likely to explode when reaches surface, found in composite volcanoes at destructive plate margins.
Describe the features of granitic magma
Low temp, High silica, viscous, sticky, gets stuck before reaches surface so not found in volcanoes.
How is Ash formed?
From material destroyed in explosive volcanic eruptions.
Define vulnerability.
How prone or likely a region is to damage and destruction from a tectonic hazard like an earthquake
What is capacity?
The ability of a community to recover from the affects of a tectonic hazard.
What is the difference between primary and secondary impacts of a tectonic hazard?
Primary: take place at the time of the event, directly caused by it.
Secondary: follow the event, indirectly caused by it
Give two primary and secondary impacts of a tectonic hazard like an earthquake.
Primary: Building destroyed, people dying/injured
Secondary: spread of illnesses, social impacts like children can’t go to school, transport issues etc.
Summarise the Kashmir earthquake.
Remote, poor region Saturday 8th October 2005 During Ramadan 7.6 on Richter Scale Epicentre at Muzaffarabad (capital of administration) 75,000 died 2.8 million homeless Property cost $440 million
Summarise the Loma Prieta earthquake.
17.04 Tuesday 17th October 1989 During evening rush hour 6.9 on Richter Scale Epicentre in mountainous part of Santa Cruz 3,757 injured 12,000 homeless Property cost $10 billion
Define preparedness and give an example
How ready governments and communities are to respond to a tectonic hazard
E.g. Warning systems, emergency plans, training for rescue teams
Define mitigation and give an example
Measures taken to reduce the effect or impact of a hazard
E.g. Moving people away, strengthen buildings
Summarise the Montserrat volcanic eruption.
Dormant eruption 1995-1997
Violent eruption - very viscous lava, pyroclastic flows, gases,avalanches
Evacuation of area - small island
Population reduced from 10,500 to just 4,000 people
Summarise the Laki volcanic eruption.
Most devastating eruption in human history 1783-4 Part of Mid Atlantic Ridge (Iceland) Poisonous gases, not explosive Livestock lost Half population killed by famine Reduced global temperatures in Europe
What do aid packs usually include?
Canned food Tents Mobile field kitchens Antibiotics Blankets Prefab toilets
How are building strengthened for tectonic hazards in the developed world?
Cross bracing Strong flexible joints Heavy appliances fastened down Resistant reinforced framework Supported diagonal steel beams Base isolator with shock absorbers Deep foundations made of layers of steel and elastic synthetic rubber Shear wall and core made from concrete steel rods
How are existing buildings strengthened for tectonic hazards in the developing world?
Thick walks
Through stones binds wall together
Wire mesh and cement overlay at wall corners
Timber frame
Cross bracing
Band of concrete stop wall moving outwards
Removal of mud overlay on roof
How are new buildings strengthened for tectonic hazards in the developing world?
Cement and sand mortar shaped stones for walls
Concrete ring beam at roof level
‘Knee braces’ - timber frame reinforced
Limit thickness of mud overlay on roof to 200mm
