Transcript How Are Igneous Rock Formed? - White Plains Public Schools

How Are Igneous Rock
Formed?
• Igneous rocks are called fire
rocks and are formed either
underground or above
ground
• Underground, they are formed
when the melted rock, called
magma, deep within the earth
becomes trapped in small
pockets
• Magma - cools slow….ly
underground forming Large
grains or crystals. The atoms
have Time to make orderly
arrangements
• Igneous rocks can also form
above ground when
volcanoes erupt, causing
the magma to rise above the
earth's surface. It will now
be called Lava
• As the lava cools above
ground it cools Quickly. The
grains or crystals do not
have time to form and
arrange themselves
• Quick cooling causes small grain
sizes and sometimes no grain
sizes at all. When grains do not
take any shape at all the term used
is called
• non-crystalline(no grains) or glassy
• Intrusive – refers to magma
that cooled slowly
underground forming large
grains or crystals
• Extrusive – refers to Lava that
cooled quickly above the
ground it forms small-tiny grain
sizes or no crystals
(
) in the rock
• Lets look at some pictures
and compare what you see
to your reference table
Lets look at some pictures
and compare what you see to
your reference table
• http://volcano.und.edu/vwdocs/vwlessons/l
essons/Slideshow/Igrocks/Igindex.html
Granite
Gabbro
Rhyolite
Basalt
Scoria (vesicular – holes in it)
Vesicular Basalt
Obsidian (non-crystalline)
Pumice
Basaltic Glass