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Flashcards in C2b Deck (12):

How are igneous rocks formed?

-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)


How are metamorphic rocks formed?

-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


How are sedimentary rocks formed?

-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


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

-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


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

-very hard
-ideal for steps and buildings


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

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


How are volcanoes formed?

-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


How do geologists try to predict volcanic eruptions?

-looking at signs that a volcano eruption might happen
-e.g.magma movement below the ground near a volcano


Why do geologists try to predict volcanic eruptions?

-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


Why do people choose to live near volcanoes?

-volcanic ash creates fertile soil


How do volcano eruptions differ?

-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


What is subduction?

-two tectonic plates colliding
-dense oceanic plate is forced underneath a less dense continental plate