MY Geography 🌏 Flashcards
4 Evidence to support plate tectonic theory
Jigsaw fit, convectional currents, fossils, geological patterns
What is the evidence of a jigsaw fit between the continents?
They all fit together
What is plate tectonic theory?
The theory that the earth’s crust is made up of large plates moving in constant slow motion. Convection currents in the mantle move the plates. The source of heat driving the convection currents is the radioactive decay which is happening deep in the earth.
What is an example of a jigsaw fit in continents?
East of South America and West of Africa
How does jigsaw fitsupport plate tectonic theory?
If all the plates fit together at a certain point, they would’ve had to move to be broken up like they are today
What is proof of convection currents?
Underwater volcanoes and mountains show something is pushingor pulling the Earth.
How do convection currents support the plate tectonic theory?
It provides a cause for the pushing and pulling of the earth.
What is an example of how the study of fossils has helped support plate tectonic theory?
Mesosaurus fossils found on west coast of africa and east coast of south america only
How does the study of fossils support plate tectonic theory?
It shows the continents were likely connected as the mesosaurus could not have swam or flown across the ocean.
What is an example of geological patterns supporting plate tectonic theory?
Coal deposits in antarctica
Why does coal being in antarctica support plate tectonic theory?
Coal is fossilised plants. Plants currently don’t grow in Antarctica so they must’ve at a certain point.
Which geologist proposed the idea of one big content being formed which he called pangaea?
Alfred Wegener
What are the names of the plates?
Pacific, NA, SA, Eurasian, African, Phillipine, Juan de fuca, indo-australian, antarctican, nazca, cocos. arabian, caribbean
Three types of boundaries
Divergent, Convergent (destructive) , Transform
What is oceanic crust?
plate that is made up of more dense rock. It sinks easily due to its
density and is constantly created at boundaries. It is ‘new
rock’ and forms our ocean bed.
What is a subduction zone?
where one plate is forced downwards below another plate and
grinds past it causing huge amounts of friction and heat.
What is a convergent (destructive) plate boundary?
where two plates are moving towards each other, one of which is
continental crust and one is made of oceanic crust
What is continental crust?
this is a plate that is made up of less dense rock. Because it is less
dense it doesn’t sink. It is exceptionally old and makes up our land
surfaces
What is a plate boundary?
where two very large crustal plates meet on the earth’s surface.
Earthquakes and volcanoes happen here.
What are fold mountains?
large mountain ranges formed by the collision and ‘folding’
of two plates as they plates continually push into one another.
What is an Ocean trench?
a particularly deep point of the ocean bed where the oceanic and
continental crust have dragged each other downwards.
What is a composite volcano?
very steep
volcano which is formed at a
destructive boundary. The
magma under the surface has
high silica and is very explosive –
these are the most dangerous
What are pyroclastic flows?
Pyroclastic flows are fast-moving currents of hot gas and rock, which reaches speeds moving
away from a volcano of up to 450 mph. The gas can reach temperatures of about 1,000 °C.
Pyroclastic flows normally hug the ground and travel downhill, or spread laterally under gravity.
What is a volcanic bomb?
A volcanic bomb is a mass of molten rock larger than 64 mm in diameter, formed when
a volcano ejects viscous fragments of lava during an eruption.
Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire
aerodynamic shapes as they cool during their flight. The largest have been evidenced in
Japanese eruptions, up to 6 metres in diameter.
What are properties of lava flows?
Lava flows destroy everything in their path, but
most move slowly enough that people can
move out of the way. Speeds can reach
30mph if it is low viscosity (runny) e.g.
Mauna Loa, Hawaii
What are lahars?
- Lahars are when a snow-capped volcano erupts, melting the snow and ice.
- They have the thickness of wet concrete, and travel at 30 miles per hour.
- This scalding water travels down the volcano, and eventually mixes with mud and debris from surrounding forests and communities.
What causes tsunamis at destructive plate boundaries?
- caused by the sudden uplift of the oceanic plate which displaces huge amounts of water.
- When these reach land, they can cause waves up to 30m high and can kill over 300,000 as it did in the Indian Ocean Tsunami.
What are some hazards of a volcano?
Pyroclastic flows, volcanic bombs, volcanic ash, lava flows, lahars,
What is an earthquake
Earthquakes are vibrations of the Earth’s crust caused by movement at
plate boundaries and major fault lines.
Where do earthquakes happen?
Earthquakes can occur at all major fault boundaries but the most
severe are usually conservative and convergent (destructive).
What is the epicenter?
The point on the surface above where an earthquake
happens is called the epicentre.
What is the focus?
The point along the fault in
the crust where an earthquake
happens is called the focus.
What are the two ways to measure an earthquake?
Richter and Mercalli Scale
What does the richter scale measure?
measures the magnitude of
the earthquake (how much the ground
shakes)
What does the mercalli scale measure?
measures the intensity of
the earthquake (based on observations of
the resulting damage)
What is a logarithmic scale?
Every 1.0 is ten times more powerful than the previous 1.0 . Eg) 5.0 = 4.0 x 10
