11. What type of rock is obsidian? How do you know?
Obsidian is a naturally occurring volcanic glass formed when felsic lava
extruded from a volcano cools rapidly with minimum crystal growth.
Igneous. Because it’s volcanic
12. What type of rock is Granite? Explain how you know.
It is formed from magma. Most of it forms deep in the crust of the Earth. Most granite
is more than a mile deep in the continental crust. Scientist still do not agree how much
of it makes its way to the surface. What type of rock is it?
Igneous. Because it’s formed from magma
13. What type of rock is Slate? Explain how you know.
Slate is formed when sedimentary or igneous rocks are exposed to conditions of very
high pressure or temperature, or are exposed to large amounts of very hot water. Slate
is formed when fine-grained sedimentary rock (shale) is buried and exposed to high
pressure deep beneath the Earth's surface.
Metamorphic. Because it’s exposed to very high temps and
pressure
14. What type of rock is Pumice? Explain how you know.
Pumice is a very light colored, frothy volcanic rock. Pumice is formed from lava that is
full of gas. The lava is ejected and shot through the air during an eruption. As the lava
hurtles through the air it cools and the gases escape leaving the rock full of holes.
Igneous because it’s coming from volcano and formed from lava
15. What type of rock is shale? Explain how you know.
It is formed when the debris or sediment becomes compacted by pressure and a rock
forms.
Sedimentary because it’s formed from sediment
16. What type of rock is Limestone? Explain how you know.
It was formed from small particles of rock or stone that have been compacted by
pressure.
17. What type of rock is Gneiss? Explain how you know.
Gneiss is a typical rock type formed by regional metamorphism, in which a
sedimentary or igneous rock has been deeply buried and subjected to high
temperatures and pressures.
Metamorphic because it’s subjected to
high temperatures and pressure
18. What type of rock is Marble? Explain how you know.
Marble is a rock formed when limestone is exposed to high temperatures
and pressures. Marble forms under such conditions because the calcite
forming the limestone recrystallises forming a denser rock consisting of
roughly equigranular calcite crystals.
Metamorphic because it forms under high temperatures
and pressure