lesson 5: igneous rocks 1/8/15. igneous rocks are rocks formed by molten, or melted rock as it cools...
TRANSCRIPT
Igneous Rocks are rocks formed by molten, or melted rock as it
cools and hardens.
This process can occur fairly quickly when
molten rock is forced to Earth’s surface, or slowly deep beneath
Earth’s crust.
Discovery Education Video:
Igneous Rocks
Intrusive igneous rocks are formed from magma (molten rock beneath
Earth’s surface).
These rocks cool slowly and will often have large mineral crystals present.
Extrusive igneous rocks are formed from lava (molten rock that is forced to
Earth’s surface).
These rocks cool quickly and will often have few, if any, mineral crystals present.
Crystals often form in igneous rocks when the molten rock cools slowly enough for
individual minerals to crystallize together.
Quartz (white)
Mica (black)
Feldspar (pink)
Many types of igneous rocks will be full of small holes. These are caused by gasses
escaping from the molten rock as it cools.