igneous rocks 1 .pptx - Igneous Rocks Overview Rock...

Igneous Rocks
Overview

Rock Definition
•
A naturally occurring, solid mixture composed of minerals, smaller
rock fragments, or organic matter.
•
Grains: the individual particles or crystals in a rock

Igneous Rocks
•
Are formed directly from the cooling of liquid rock (magma or lava)
•
Magma is liquid rock underground
•
Lava is liquid rock on the surface of Earth

Igneous
rocks
overview:
•
Extrusive Igneous rocks
form on the surface
•
Intrusive Igneous rocks
form underground

Nature of Magma
•
Minerals freeze/solidify (transition from liquid to solid) at very high
temperatures, from hundreds °C to > 1,000 °C
•
Magma must cool below the freezing/solidification temperature of a
mineral in order for it to begin crystallizing

Intrusive Igneous Rocks
•
Intrusive Igneous rocks:
•
form inside the earth’s crust
•
Olivine, Pyroxine, Plagioclase feldspars crystalize first, at higher
temperatures
•
These solidified minerals then to settle at the bottom of a pool of magma
because they are more dense
•
Later-forming, less dense minerals tend to form at lower
temperatures and float to the top of a magma pool

Igneous rocks rates of cooling