Transcript Igneous Rock

Igneous Rock 12/1/14
4-2 pgs. 87-90
IN: Explain, using words
and pictures, how rocks
form.
sedimentary
compaction,
rock
cementation
metamorphic
rock
sediment
igneous
rock
magma
How are igneous rock formed?
 Rocks are heated enough to melt its minerals
into magma.
 Magma cools into various types of igneous
rock depending on the composition of the
magma and the amount of time it takes the
magma to cool and solidify.
How are igneous rock classified?
 Like all other rock, igneous rock is classified
according to its composition and texture.
How does magma form?
 Temperature
 An increase in temperature deep within the
Earth’s crust can cause the minerals in a rock to
melt.
 Different minerals melt at different temperatures,
from about 700 to 1250 degrees Celsius.
How does magma form?
 Pressure
 The high pressure deep within the earth forces
minerals to stay in the solid state, so when hot
rocks rise to shallow depths the pressure is
released and they melt.
How does magma form?
 Composition
 Sometimes fluids like water and carbon dioxide
enter a rock that is close to its melting point.
 Remember, water melts above 0 degrees
Celsius and carbon dioxide melts above -78
degrees Celsius.
Composition
 Felsic - light-colored (Light as a Feather)
 Less dense…light
 Rich in elements such as silicon, aluminum,
sodium and potassium.
Granite, Obsidian,
Pumice
Composition
 Mafic - dark-colored (dark as Midnight)
 More dense…heavy
 Rich in elements such as iron, magnesium, and
calcium
Basalt
Texture
 Intrusive Igneous Rock
 When magma cools beneath the Earth’s
surface.
 Coarse-grained texture
 Cools slowly
Granite & Basalt (because
the pressure of the ocean
makes the crystals small)
Big amount of time=Big
crystals=Coarse Grain
Texture
 Extrusive Igneous Rock
 When lava cools on the Earth’s surface.
 Fine-grained texture
 Cools quickly
Small
amount of
time=
small
crystals
Pumice & Obsidian
Granite
 Igneous plutonic rock formed when magma cools
slowly.
 Remember it’s made up of mica, feldspar, and
quartz...all silicates.
 Felsic
 Intrusive
 Coarse-grained
Basalt
 Igneous volcanic rock with small crystals made
when lava cools.
 Mafic
 Intrusive/Extrusive
 Fine-grained
Obsidian
 Igneous rock formed from volcanoes that has
sharp edges and looks like glass.
 Felsic
 Extrusive
 Fine-grained
Pumice
 Igneous rock with holes and can float on water.
 Felsic
 Extrusive
 Coarse-grained
OUT: What are some
features of igneous rocks?