Download Igneous Rock PPT - Effingham County Schools

Igneous Rocks
Igneous
Metamorphic
Sedimentary
3 types of rocks

Igneous rocks are formed from molten
rocks that has cooled and hardened.
Ship Rock, New Mexico
Formed when magma in a volcano cooled slowly
Igneous Rocks

Magma (or Lava) cool and crystallize to
form igneous rock.
Igneous Rocks

There are two
types of Igneous
Rock. Intrusive
and Extrusive
Igneous
Rocks

Extrusive Igneous Rock is formed from
lava, which is on the surface.

Intrusive Igneous Rock is formed from
magma, which is below the surface.

What is the difference between magma
and lava? Lava is on the earth surface
and magma is below.

Molten rock that flows on the surface of
the Earth is lava.

Molten rock that is below the surface of
the Earth is Magma.

Intrusive— large crystals
◦ WHY? The inside of the Earth is VERY hot!
Therefore, the magma cools slowly creating
larger crystals

Extrusive— small crystals
◦ WHY? Earth’s surface is much cooler, and
lower temperatures mean rocks cool quickly,
not leaving enough time for large crystals to
form.
Textures of Igneous Rocks

Igneous rocks are dominated by silicate
minerals.
Silicates

Molten rock with lower amounts of silica
flows faster than molten rock with higher
amounts of silica.

If lava has more silica, it will move slower
than lava with less silica.
Lava spread = small amounts of silica
Explosive eruptions = large amounts of silica
Extrusive Igneous Formations

Where are many Igneous Rocks found?
Divergent boundaries and volcanoes.

Igneous rock undergoes weathering (or
breakdown) to form sediment.

So it becomes……………………
◦ Sedimentary Rock
The Rock Cycle

Of the following three types of rocks,
igneous rocks are the hardest.
Igneous Rocks
Stone Mountain

The Stone Mountain granite is a relatively
small granite pluton that covers an area
less than a county in size.
Stone Mountain

Stone Mountain is made of granite and is
an igneous rock.
Stone Mountain

Magma that cools and hardens forms an
intrusive igneous rock

Lava that cools and hardens forms an
extrusive igneous rock