Download Section 4-2

Section 4-2
• How are igneous rocks formed?
• What is the difference between magma and
lava?
• What is the difference between intrusive and
extrusive rocks?
• Describe the 3 types that igneous rocks can be
classified into.
• Igneous rocks are formed when molten
material from a volcano or from deep inside
the Earth cools and hardens.
• Magma is molten rock that is beneath the
Earth’s surface and lava is magma that has
reached the Earth’s surface and flows from a
volcano.
• Intrusive rocks are igneous rocks that form
below the Earth’s surface.
• They cool slowly and have large mineral
grains.
• Extrusive rocks are igneous rocks that form
when lava cools on or near the Earth’s surface.
• They cool quickly and have a fine-grained
texture.
• Sometimes the lava cools so quickly that air
bubbles get trapped in the lava leaving behind
holes in the rock.
Types of Igneous Rocks
• Basaltic – are dense, heavy, and dark-colored;
are rich in iron and magnesium; are produced
by Hawaiian volcanoes
• Granitic – are light-colored and less dense;
contains a lot of silicon and oxygen; can cause
violent volcanic eruptions
• Andesitic - have mineral compositions
between basaltic and granitic
Basaltic
Granitic
Andesitic
Igneous rocks are the most abundant
type of rock on Earth.