Year 9 Fragile world revision Flashcards
What is the earths structure
Crust
Mantle
Outer core
Inner core
What are the 5 pieces of evidence of plate tectonics
Jigsaw fit Convection currents Study of fossils Geological patterns Paleomagnetism
What is jigsaw fit
This is the theory that some countries fit together like in a jigsaw puzzle e.g. Africa and south America. This is because they were all one landmass called Pangea and overtime it broke up into smaller continents like the ones today. This supports continental drift
How do convection currents move
At the core, vast amounts of heat is given off because of radioactive decay. The rock nearest the core gets heated up and becomes less dense which causes the molten rock to rise. In the upper mantle temperatures are cooler and so the molten rock cools down and becomes more dense. This process repeats. Which proofs continental drift
What is the study of fossils
Similar fossils have been found in different continents which is evidence that these land masses were once joined together as such species could not cross oceans and so must have lived on the same land mass such as the Lystrosaurus which was found in Africa, India and Antartica. Which supports continental drift
What are Geological patterns
Similar patterns of rock in different continents is evidence that these rocks were once close to each other or joined. Similar patterns of rock have been found in Australia, S.America, Antartica and Africa. Coal has been found in Antartica which requires warm climate to form which indicates that it was once found near the equator. Which supports continental drift
What is continental drift
The idea that continents are slowly shifting there position over time
What is paleomagnestism
Along the Atlantic Ridge lava from shield volcanos have cooled and the iron in the lava is pulled towards the magnetic pole at the time before cooling. The magnetic pole switches from north to south every 100million years and the iron has is pointing in different directions depending on the time period it cooled in. This is proof of seafloor spreading.
What does viscous mean
Viscous is how runny or thick the lava is once it has erupted a highly viscous lava would be very slow moving and thick as it is high in silica but lava with little viscosity due to its lack of silica would be very runny and fast.
What are plate boundaries
Where to large crustal plates meet on the earths surface. Earthquakes and volcanos happen frequently here
What are destructive plate boundaries
Where to plates are moving towards each other one being a continental plate and the other an oceanic plate such as the Nazca and South American plate
What is continental crust
This is a plate made up of less dense rock. Because it is less dense it doesn’t sink and is extremely old and makes up are land surfaces.
What is Oceanic crust
A plate that is made up of more dense rock which sinks easily and is constantly created at boundaries. It is comparatively young and forms are Ocean beds
What is the subduction zone
Where one plate is forced downwards below another plate and grinds past in causing huge amounts of friction and heat
What is the Ocean trench
A particularly deep point of the ocean bed where the oceanic and continental crust have forced each other downward
What are fold mountains
Are large mountain ranges formed by the collision and folding of of two plates as they continually push into each other
What is pyroclastic flow
A superheated mass of rock,ash and gas that moves at over 450mph at a temperature of about 1000degrees C
What are composite volcanos
Very steep volcanos which are formed at a destructive boundary. The magma is high in silica and is very viscous so the volcanos dont erupt very much but are very explosive and dangerous when they do.
What is a conservative plate boundary
When to plates are moving past each other, this can been they are going in opposite directions or be moving at different speeds like the pacific (6cm a year) and North American (1cm a year) plates
What is a Divergent (constructive) plate boundary
Two plates are moving away from each other driven by convection currents
What are collision boundaries
Where two plates of the same density (usually continental plates) meet and push together -since they are the same density they both rise pushing against each other creating fold mountains
What kind of volcano is in Montserrat
Convergent (destructive) volcanos
Give 3 economic effects of the Montserrat erruption
Volcanic ash was sold and Montserrat now earns income from geothermic heat and quarrying in mines-secondary effect
Before the eruption Montserrat had an export economy based on agriculture, clothing, electronic parts and plants. Its GNP/person of $5000-primary effect
Tourism has now increased to see the volcano. This has created jobs and trip advisor rated it top trip of 2010- secondary effect
Name 3 social effects of the Montserrat erruption
The population declined from 12000 to 3000 due to the risk secondary effect
Over 20 villages and 2/3 of buildings were destroyed causing people to become homeless or with no jobs- primary effect
Volcanic ash contains quartz that causes silicosis which affects breathing. People today still suffer.-secondary effect
