Unit 1 - Hazardous Earth Flashcards
On average, how thick is the earths crust?
50km
How thick is the mantle?
2900km thick
What are the two parts of the mantel?
Lithosphere and asthenosphere
How thick is the outer core?
2266km
What is the temperature of the inner core?
5700 C
What is the lithosphere
The uppermost layer of the earth, the top part of the mantle and the crust
What is the asthenosphere
Part of the mantle, semi molten layer beneath the tectonic plates
Give 3 points about continental crust
Thick granite (10-15 miles)
Low density
Floats high on mantle
Give 3 points about oceanic crust
Very thin (1-3 miles)
High density
Basalt rock
What is the difference between oceanic and continental crust
Oceanic crust is below water, continental crust is below ground
Where is the heat from the earth from? (2)
50% from radioactive decay
50% from the Big Bang
Why do tectonic plates move?
Due to convection currents
Explain what convection currents are
When the rock is heated near the core, it rises, travels across and cools when get closer to the surface.
Why is the earths crust unstable? (2)
Plates are moving
Plates move in different directions
What is continental drift?
250 million years ago, the land masses were one big continent called Pangea. They slowly began to drift away into the continents we know today
Give 3 pieces of evidence for continental drift
The fossil of the Mesosaurus are found in Africa and South America yet it can’t swim long distances
Some continents interlock like a jigsaw
Plants and animal fossils are similar in India and Australia
What are the 4 types of plate movements?
Collision, convergent, divergent and conservative
What is a divergent movement?
Moving away form each other (both oceanic)
What is a collision movement?
Moving towards each other (both continental)
What is convergent movement.
Oceanic plate sub-ducts beneath a continental plate
What is conservative movement?
Sliding past each other (both continental)
What is a hotspot?
A place in the centre of a plate where magma rises
How does a hotspot cause the formation of a volcano?
The hotspot causes the lithosphere to melt so magma pushes through the crust
Where can volcanoes form?
Plate boundaries
Middle of plates e.g hotspots
What does the volcanic explosivity index show
It measures the destructive power from 1 (lowest) to 8 (highest)
What are volcanic bombs?
Large pieces of rock ejected from the volcano
What is a volcanic cloud?
Gas, steam and ash escaping from the volcano
What is pyroclastic flow?
Hot gas and volcanic matter from the volcano
What forms the sides of a volcano that was formed from a hotspot
Layers of pyroclastic flow over time
What are the two types of volcano?
Composite and shield
What is a composite volcano (shape, lava, frequency, plate boundaries)
Pointes / coned
Viscous (sticky)
Very rare, value of 6
Convergent
What is a shield volcano? (shape, lava, frequency, plate boundaries)
Quite flat and broad
Runny and quickly spreads
Very frequent, value of 1 or 2
Divergent
Give an example of a composite and shield volcano
Pinatubo
Queen Mary’s Peak
How did the Montserrat eruption happen? (2)
North and South American plates sub ducted under Caribbean plate
The me,ted plate was less dense so magma rose
Where is Montserrat? (2)
Caribbean on a small island
North America
Give 3 primary effects of the Montserrat eruption
2000 people left straight away
9000 in total left
Killed 19 people