what is the temperature and structure of the lithosphere?
how thick is the lithosphere?
over 100km is places
What is the mantle?
The solid section between the crust and the core
What are the temperature and structure of the mantle?
near the crust = very rigid
as you go deeper... temperature increases
becomes less rigid and can slowly flow, semi liquid
How big is the earth's core?
just over half the earth's radius
Is the inner core solid or liquid?
is the outer core solid or liquid?
What creates a lot of heat inside the earth?
What is the effect of the heat of created inside of the earth?
heat creates convection currents in the mantle
these cause the plates of the lithosphere to move
What are tectonic plates?
big rocky rafts
float on the mantle
less dense than the mantle
What speed do the plates move?
2.5 cm per year
What happens when plates meet?
volcanoes and earthquakes can happen
Why can't you study the inner structure of the earth?
The crust is too thick to drill through
What are seismic waves?
used by scientists to study earth's structure
they are shock waves
produced by earthquakes or man-made explosions on earth's surface
measure time for waves to travel and where they are detected draw conclusions about structure
What are the two types of seismic waves?
How are the two types of seismic wave used?
S-waves travel through solids but not liquid.
S-waves travel through the mantle.
Mantle is therefore solid.
S-waves do not travel through core (not seen in core's shadow).
Therefore outer core must be liquid.
P-waves travel faster through the middle of the core therefore suggests inner core is solid.
Who, and when, hypothesised that Africa and South America had previously been one continent?
What evidence was found for theory of continental drift?
matching layers in rocks in different continents
similar earthworms in South America and Africa
observations not previously explained inc
fossils of very similar plants and animals
coastline of Africa and S America seem to fit together
fossils of sea creatures in alps
What is the theory of continental drift?
300 million years ago one supercontinent
broke into smaller chunks
still slowly drifting apart
based on theory of plate tectonics
Why wasn't continental drift theory accepted at first?
was big change
movement wasn't detectable
said caused tidal forces and earths rotation which was shown by other geologists as impossible
It did explain things which couldn't be explained by land bridge theory (continents linked by land bridges which have sunk) such as mountains - continental drift says due to continents smashing into each other
When did scientists investigate mid-atlantic ridge?
Mid Atlantic ridge investigation - what was found about under water mountains?
magma (molten rock) rises up through sea floor
roughly symmetrical either side of ridge
suggests sea floor spreading at about 10 cm / year
Mid Atlantic ridge investigation - what was found due to magnetic orientation?
iron particles align themselves with Earth's magnetic field
as cool set in position
every half million years earth's magnetic field swaps direction.
rock either side has bands of alternate magnetic polarity
proved sea floor created as continents moving apart
What are volcanoes?
molten rock (magma) emerges through Earth's crust from mantle
if pressure then violently erupts
magma becomes lava when erupts
Oceanic and continental crusts collide - what happens?
crust of ocean floor is denser than crust below continents
two tectonic plates collide - a dense oceanic plate will be forced underneath a less dense continental.
This is called subduction.
Oceanic crust tends to be cooler at the edges of a tectonic plate - so edges sink easily pulling the oceanic plate down.
As oceanic crust forced down it melts and starts to rise.
if this molten rock finds way to surface volcanoes form
What is igneous rock?
made from any sort of molten rock cooling down and solidifies
I think its a funny word
lots of rocks on earth surface formed this way
what effects the type of igneous rock formed?
composition of the magma
how quickly it cools
name two types of magma and info on them?
iron rich basalt
lava from eruption is runny. Fairly safe (as safe as you can be with molten rock at 1200 degrees C!)
silica-rich rhyoliteeruption is explosive. Thick lava violently blown out of the top.
How do geologists predict volcanic eruptions?
study magma movements below the ground near to a volcano
still unpredictable but saves lives
What are the three types of rock?
How is sedimentary rock formed?
Layers of sediment laid down in lakes or seas
Millions of years, layers get buried under more layers and the weight pressing down squeezes out the water
Fluids flowing through the pours deposit natural mineral cement
What is limestone?
A sedimentary rock
Mostly formed from seashells
Mostly calcium carbonate
Grey/white in colour
Most shells crushed, but still quite a few fossilised shells too
What is thermal decomposition?
When one substance chemically breaks down into at least two new substances when it is heated
What is the word equation for limestone thermal decomposition?