C2A - Volcanos & Rocks Flashcards
Where is the molten rock from ? How does it get out ?
From the mantle and it emerges through the earths crust
What are volcanos formed by ?
Molten rock
Once magma has risen through the crust what happens ?
It boils over
If the pressure is released suddenly what happens ?
The magma will emerge quite violently
What’s the difference between magma and lava ?
They are the same thing but inside the mantle. It’s called magma. When it erupts it’s called Lava.
There is crust at both the ocean floor and below the continents. Which one is more dense ?
The ocean floor crust
What is subduction ?
When two tectonic plates collide. The dense oceanic plate will be forced under the continental plate.
If oceanic crust is cooler at the edges what result could this have ?
The edges sink easily. Pulling the oceanic plate down.
What happens when the oceanic crust is forced down ?
It melts and starts to rise. If the magma gets to the surface. You have a volcano
Why do geologists study volcanos ?
To see if there are signs of a soon volcanic eruption
What things do scientists use to help the study volcanos ?
Magma movement
What is there more of with the prediction of volcanos than there was in the past ?
Accuracy
Why is it tricky to predict volcanos ?
They are very unpredictable
What are the three different types of rock. And an example ?
Sedimentary - Limestone
Metamorphic - Marble
Igneous - Granite
How is igneous rock formed ?
When molten rock cools down and solidifies
If a volcano has a safe eruption. What type of magma is produced ?
Iron rich basalt. It is runny
If the eruption is dangerous what magma is formed ?
Silica rich rhyolite
The igneous rock that is formed depends on the cooling time of lava. Explain ?
Fast cooling = small crystals
Slow cooling = large crystals
There are three steps in the formation of sedimentary rock. what are they ?
1) formed from layers of sediment in lakes or seas
2) over millions of years layers get buried over more layers. The pressure squeezes out the water
3) fluids flowing through the pores deposit natural mineral cement
Limestone is mostly formed from what ?
Sea shells
What is the equation for the thermal decomposition of limestone ?
Calcium Carbonate = Calcium Oxide + Carbon Dioxide
How is metamorphic rocks formed ?
By the action of heat and pressure on sedimentary or igneous rocks over long periods of time
What is the same in most metamorphic rocks ?
The chemical composition
What do limestone and marble have in common ?
Both forms of calcium carbonate
How is marble made from limestone ?
very high temps and pressures break down the limestone and it reforms as small crystals
