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
-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?
-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