Hazards BK 2 - Plate Tectonics Flashcards
How old is the Earth said to be?
4.5 billion years old
List the earths internal structure from the middle to the outside
Inner core, outer core, lower mantle, asthenosphere, upper mantle, crust
What is the crust and upper mantle collectively called?
The lithosphere
What is the radius of the Earth proximately?
over 6000 km
what are the two different types of crust called?
Oceanic and continental
what separates the crust from the mantle?
The Mohorovičić (MOHO) discontinuity
What is beneath the lithosphere and could be described as semi molten
The asthenosphere
What are the two elements that the mantle is made up from?
Silica and oxygen
What is the thickness of the mantle?
2900 km
What state is the outer core?
Semi molten/liquid
what is the thickness of the inner core?
5100 km
What is the state of it inner core?
Solid
What alloys are always found in the earths core
Iron and nickel
What is the temperature of the earths inner core?
5 to 6000 Celsius
what is the type of heat called That’s left from the earths formation.
Primordial heat
what is the type of heat produced by radioactive decay of isotopes?
Radiogenic heat
What is Alfred Wegeners theory of plate tectonics that the majority of people believe?
the earths crust and upper mantle layer is cracked and divided into a series of plates that float on the semi molten asthenosphere
why is the continental crust nicknamed sial
Because it is dominated by silica, rich, minerals, and aluminium
why is the oceanic crust nicknamed sima
Because of the silica in magnesium content
what are some factors of the continental crust?
older, lighter, thicker, made of granite, lighter in colour, contains silica and aluminium and can be uplifted
what are some characteristics of the oceanic crust?
Younger, heavier, thinner, middle of basalt, darker in colour, contain silica and magnesium, and sink
what does wegeners theory of plate tectonics centre around?
The idea that the different crustal plates move in different directions due to convection currents in the mantle, cause in continental drift
What was the supercontinent called when all landmasses were joined together
pangeae
What are some geological evidence for plate tectonics?
South America and west Africa fit together perfectly
rock sequences in northern Scotland closely agree with one is found in eastern Canada
carboniferous glaciation formation deposits are both found in Antarctica and India, so must have formedtogether, then moved apart
What are some biological evidence for plate tectonics?
fossil brachiopods found in Indian limestone are comparable with ones found in Australia
Fossil remains of the reptile mesosaurus are found in South America and South Africa
What is palaeomagnetism also known as seafloor spreading?
The study of ancient magnetic fields
what are constructive margins also called?
Divergent plate boundaries
What is a constructive margin?
Where plates are moving apart are away from each other
what is an example of a constructive margin
Where the North American plate meet the Eurasian plate in the middle of the Atlantic Ocean
how do constructive plate margins work?
The two plates move apart through seafloor spreading, as they pull a part subsidence happens, and a rift Valley is formed. This creates a weakness where by magma can penetrate, creating a mid ocean ridge in terms of a volcano.
What types of hazards occur at a constructive plate margin?
Earthquakes volcanoes are the main hazard
what is a collisional margin also known as
Destructive plate boundaries
explain what happens at a collisional margin
Where two continental crust plates move together or towards each other
How are food mountains formed at a collisional margin
Neither continental plate is subducted, which causes uplift to occur. This creates many fold mountains.
What is an example of a collisional margin
where the Eurasian plate meets the Indian plate where are the Himalayas are found
What hazards occur at a collisional margin?
Earthquakes
why can Earthquakes not happen at a , collisional plate margin
There is no subduction that happens here
what is a conservative margin also called
A transform boundary or fault
What happens at a Conservative margin?
Where two plates move alongside each other, sometimes in opposite directions, but mostly in the same direction
What process occurs at a Conservative margin?
both plates will eventually Jerk apart leading to an earthquake
What is an example of a Conservative plate margin
why, the Pacific plate and North American plate moves alongside each other in the same direction
What is the fault called where the North American and Pacific plate meet?
The San Andreas fault
Do volcanic eruptions happen at a Conservative plate margin
No, because there is no subduction
what sort of plates are involved at a destructive plate margin?
Continental and oceanic or oceanic and oceanic
What is an example of a destructive plate margin involving a continental and oceanic plate
where are the South American plate is moving towards the oceanic nasca plate where are the Andes are found
what happens when a continental and oceanic plates meet at a destructive plate margin?
The continental crust is uplifted on the oceanic crust is subducted, which creates a chain of fold mountains
do both volcanoes and earthquakes happen at a continental and oceanic destructive plate margin
Yes
What is increased where 2 oceanic plates meet at a destructive plate margin?
Subduction
What is created at both a continental and oceanic plate and oceanic and oceanic plate
A deep sea trench
what is also created when two oceanic plates converge at a destructive plate margin
A volcanic island arc
What is an example of where two oceanic plates meet
Where are the Pacific and the Philippine plates move together create in the Marianas Trench
can volcanic and seismic activity take place away from plate margins
Yes
what percentage of earthquakes occur away from plate margins
10%
What are hotspots?
Hotspots are found within tectonic plates were, the crust is thin, so McMacken rise to the surface, escaping through cracks
what do hotspots tend to create
Shield volcanoes
What is gravitational sliding also known as ridge push?
When gravity causes old and denser lithosphere to slide away from the middle ocean ridge
what are deep sea trenches
where oceanic and continental plates meet, the denser plate is forced under the light one which causes a deep trench in the ocean
what are rift valleys
a lowland region that forms when tectonic plates move apart, found on land and in the ocean (created by sea floor spreading)
what are island arcs
where heat from subduction and friction begins to melt a plate, it begins to rise towards the surface as magma, these eventually reach the surface to form complex volcanoes
what is slab pull
as a plate moves down into the mantle it pulls the rest of the crust on that plate with it
what are some arguments supporting plate tectonics
long standing theory so has some truth
associated with other theories like continental drift
a lot of landforms have been created by tectonics
what are some arguments supporting gravitational sliding
convection currents lack power to move in various directions meaning the plate theory can’t be fully true
both slab pull and ridge push explain what happens at opposite ends of plates
