Transcript Table of Contents - Mr. Tobin's Earth Science Class

Table of Contents
Title: Metamorphic Rocks
Page #: 45
Date: 12/04/12
Objective
 Students will be able to recognize
metamorphic rocks.
 Students will be able to explain the
processes by which rocks are
metamorphosed.
Word of the Day
 Metamorphosis: A change in form.
Recognizing Metamorphic
Rocks
 Metamorphic Rocks: Rocks that have been
changed.
 Metamorphic Rocks are pre-existing rocks that
are exposed to increases in temperature and
pressure, or hydrothermal solutions, that change
the rock’s texture, mineral composition, or
chemical composition.
Recognizing Metamorphic
Rocks
 Increases in temperature and
pressure do not melt the rock,
but they do change it.
 High temperatures come from
Earth’s interior.
 Rocks are either buried or located
near igneous intrusions (magma
pockets.)
 High pressures come from
deep burial or from
compression during mountain
building.
Recognizing Metamorphic
Rocks
 Metamorphic Minerals - Metamorphism changes
minerals that are present in rock to new minerals “solid state alterations.”
 Specific minerals are associated with specific
conditions during metamorphosis.
Recognizing Metamorphic
Rocks

Metamorphic Textures:
2 Kinds:
1. Foliated: Layers and bands or minerals (stripes.)
Bands always form perpendicular to pressure.
Example: Gneiss - formed from granitic rock.
2. Nonfoliated: Minerals that form blocky crystal shapes.
Examples: Quartzite - formed from quartz rich sandstone.
Marble - formed from limestone.
Recognizing Metamorphic
Rocks
Quartzite - Nonfoliated
Gneiss - Foliated
Recognizing Metamorphic
Rocks

Porphyroblasts:
Large crystals that
have grown in solid
rock. Surrounded
by smaller crystals.

Example: Garnet