Igneous Rocks Basics
Which process turns magma or lava into solid rock?
Crystallization/Freezing/Cooling
On the surface of Earth
What are the 3 main factors that determine whether a rock will melt?
Temperature, pressure, and water content
Which type of igneous rock forms from magma cooling underground?
Intrusive
What do we call a very large mass of intrusive rocks that forms deep underground?
Batholith
What are igneous rocks made out of?
Cooled/crystallized magma/lava
Where is magma found?
Underground
Why do some rocks remain solid deep underground even at high temperatures?
High pressures can keep the rocks solid
Which type of igneous rock forms from lava cooling on the surface of the Earth?
Extrusive
What is a thin sheet of igneous rock that forms between horizontal rock layers?
Sill
What are the three main components of magma?
Melt (liquid), solid(crystallized) minerals, and dissolved gases (volatiles)
Which substance is hotter: magma or lava?
Magma
It lowers the melting point, allowing the rock to melt
What is the most common felsic igneous rock?
Granite
What is a thin wall of igneous rock that cuts across pre-exisiting rock layers (vertical intrusion)?
Dike
Intrusive(felsic) or Extrusive(mafic)
Why does lava have more minerals than magma?
As the magma rises towards earths surface, it rocks surrounding rocks which adds mineral to the melt
At what location does water typically get introduced to rocks, and therefore melt them?
At subduction zones
What is the most common mafic igneous rock?
Basalt
What type of igneous rock feature is saucer shaped and deforms the rock layers below it?
Lopolith
What is the difference between mafic and felsic igneous rocks?
Felsic rocks are light-colored and high in silica; mafic rocks are dark-colored and low in silica.
What happens to gases in magma when it reaches the surface?
They are released due to a drop in pressure, like opening a soda bottle.
How does water influence rock melting?
Water weakens bonds between minerals, lowering the melting point
How does silica (quartz) content affect the color of an igneous rock?
The more silica(quartz) there is in the magma, the lighter in color the rock will be (and vice versa)
Why do batholiths sometimes become exposed at the surface?
Erosion and weathering remove the overlying rock, revealing the batholith