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Flashcards in C2b Deck (12)
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1
Q

How are igneous rocks formed?

A
  • made when molten rock cools down and solidifies
  • igneous rock type depends on how quickly the magma cooled and the composition of magma
  • various minerals
  • randomly interlocking crystals
  • big air gaps, means it cooled down slowly (inside volcano)
  • small air gaps, means it cooled down quickly (outside volcano)
2
Q

How are metamorphic rocks formed?

A
  • heat and pressure on sedimentary igneous rocks over long periods of time
  • mineral and texture may be different to original rock, but chemical composition is the same
  • as long as the rock doesn’t melt it is classified as metamorphic
  • if it melts and turns to magma its gone
3
Q

How are sedimentary rocks formed?

A
  • layers of sediment laid down in lakes or seas
  • buried in more layers over millions of year
  • weight presses down and squeezes out the water
  • fluids flowing through pores deposit natural mineral cement
4
Q

Give an example of a metamorphic rock and what are the properties?

A
  • marble
  • a form of calcium carbonate
  • very high temperatures and pressures break down the limestone and reforms as small crystals
  • giving marble a more even texture and making it harder
5
Q

Give an example of a igneous rock and what are the properties?

A
  • granite
  • very hard
  • ideal for steps and buildings
6
Q

Give an example of a sedimentary rock and what are the properties?

A

-limestone
-mostly formed from seashells
original shells mostly crushed, but fossils can remain

7
Q

How are volcanoes formed?

A
  • oceanic plates are denser than ontinental plates
  • oceanic plates are also cooler at the edges –edges sink easily, pulling the oceanic plate down
  • as the oceanic crust is forced down underneath continental crust (subduction) it melts and starts to rise
  • if this molten rock finds a way to the surface volcanoes form
8
Q

How do geologists try to predict volcanic eruptions?

A
  • looking at signs that a volcano eruption might happen

- e.g.magma movement below the ground near a volcano

9
Q

Why do geologists try to predict volcanic eruptions?

A
  • to try and find out if there are signs a volcano may erupt soon
  • spotting these things means scientists can predict eruptions with greater accuracy than in the past
  • tricky as volcanoes are unpredictable
  • scientists can most likely just say when an eruption is more likely to happen than usual
10
Q

Why do people choose to live near volcanoes?

A

-volcanic ash creates fertile soil

11
Q

How do volcano eruptions differ?

A
  • volcanoes that form iron-rich basalt, eruptions have runny lava and eruptions are safer
  • silica-rich rhyolite magma, eruptions are explosives, producing thick lava that can be blown violently from the top
12
Q

What is subduction?

A
  • two tectonic plates colliding

- dense oceanic plate is forced underneath a less dense continental plate