Notes: Types of Rocks
4.2: Igneous
Rocks
- Igneous
rocks are classified according to their origin, texture and mineral
composition
- Origin-
Extrusive vs. Intrusive
- Extrusive
are formed from lava that has erupted onto the surface
- Also
called volcanic rocks
- Examples: basalt, pumice, rhyolite
- Intrusive
form with magma solidifies under the surface
- Also
called Plutonic Rocks (Pluto was Greek Ruler of Underworld)
- Examples: granite, gabbro
- Texture
- Coarse-grained: grains can be easily seen with naked
eye
- Fine-grained: grains can be seen with a microscope
- Glassy: rocks have no grains
- Mineral
Composition
- Color
is clue to composition
- Magma
that is low in silica has dark colored rocks
- Magma
that is high in silica has light colored rocks
- Uses
of Igneous Rocks
- Building
Materials
- Granite
used in homes- walkways, bathrooms, kitchen
- Basalt
used to make gravel
- Other
Uses
- Obsidian
is used to make sharp tools for cutting
- Pumice
is a good abrasive for cleaning and polishing
4.3: Sedimentary
Rocks
- From
Sediment to Rock- most sedimentary rocks are formed through a series of
processes: erosion, deposition,
compaction, and cementation
- Erosion-
breaking down of the sediments and moving it
- Deposition-
depositing sediments in a new location
- Compaction-
presses the sediments together
- Cementation-
dissolved materials “glue” the sediments together
- Types
of Sedimentary Rocks
- Clastic-
forms when rock fragments are squeezed together; fragments range greatly
in size
- Organic-
forms when the remains of plants and animals are deposited in thick
layers
- Chemical-
form when minerals dissolved in a solution crystallize
- Uses
of Sedimentary Rocks
- Used
for many purposes including building materials and tools
4.5: Metamorphic
Rocks
- Changes
in the structure, appearance and composition of rock beneath the surface
- Is
caused by heat and pressure
- Types
of Metamorphic Rocks
- Foliated-
have their grains arranged in parallel bands or layers
- Foliated
rocks may split along their bands
- Nonfoliated-
mineral grains are arranged randomly
- Contact
vs. Regional Metamorphism
- Contact: magma intrudes rock-heat from magma
alters the rock-rock in contact with magma “cooks” first-minerals in
magma and rock mix-new mineral combinations from
- Only
affects a small area of rock- rock touching magma
- Regional: occurs when some rocks are in contact
with a magma chamber or at the margins of the continents
- Affects
a large area of rocks
- Uses
of Metamorphic Rocks
- Building
and sculpture
- I.e.
marble is used for buildings, floors, etc