C2b

Question 1

How are igneous rocks formed?

Answer 1

• 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)

Question 2

How are metamorphic rocks formed?

Answer 2

• 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

Question 3

How are sedimentary rocks formed?

Answer 3

• 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

Question 4

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

Answer 4

• 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

Question 5

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

Answer 5

• granite
• very hard
• ideal for steps and buildings

Question 6

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

Answer 6

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

Question 7

How are volcanoes formed?

Answer 7

• 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

Question 8

How do geologists try to predict volcanic eruptions?

Answer 8

• looking at signs that a volcano eruption might happen

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

Question 9

Why do geologists try to predict volcanic eruptions?

Answer 9

• 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

Question 10

Why do people choose to live near volcanoes?

Answer 10

-volcanic ash creates fertile soil

Question 11

How do volcano eruptions differ?

Answer 11

• 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

Question 12

What is subduction?

Answer 12

• two tectonic plates colliding

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