Transcript Rocks: Mineral Mixtures

Igneous Rocks
What is an igneous rock?
• Born from fire
• Any rock that
forms from
magma or lava
• Most contain
mineral crystals
vent
lava
land surfac
e
conduit
magma
Anatomy of a Volcano
Characteristics of Igneous Rocks
• Classified according to their…
–Origin
–Texture
–Mineral composition
Origin
• Extrusive Rock- formed from lava that
erupted onto Earth’s surface (ex.
Basalt)
• Intrusive Rock- igneous rock that
formed when magma hardened
beneath Earth’s surface (ex. Granite)
Granite
Basalt
Texture
•
•
•
•
Fine-grained
Coarse-grained
Glassy
porphyritic
Fine-Grained
• Rapid cooling
lava
• Small crystals
• Extrusive rocks
Coarse-Grained
• Slow cooling
magma
• Large crystals
• Intrusive rocks
Porphyritic
• Large crystals scattered on a
background of much smaller
crystals
• Intrusive rocks cool in 2 stagesrate of cooling is changed from
slow to fast
What is the texture of the rock?
Flow banding
Mineral Composition
• Lava that is low in silica- dark
colored rocks
• Magma high in silica- light colored
rock
Uses of Igneous Rocks
• Igneous rocks are hard, dense, and
durable so they are used for
–Tools
–Building materials
• Granite- long history of building
material
Sedimentary Rocks
What is a sedimentary rock?
• Composed of sediments derived from
pre-existing rocks or by the
crystallization of minerals that were held
in solutions
• Sediment- small, solid pieces of material
that come from rocks or living things
• Can include fossils, leaves, etc.
How do the sediments turn into a
rock?
1.
2.
3.
4.
Erosion
Deposition
Compaction
Cementation
Erosion
• Water, wind, or ice loosen and
carry away fragments of rock
Deposition
• That’s when sediments stop
traveling by water or wind and
settle
Compaction
•
•
•
•
Sediments fit loosely
Years go by…thick layers build up
Layers are heavy and press down
Compaction- process that
presses sediments together
(squeezes)
Cementation
• During compaction…minerals
dissolve in water
• Dissolved minerals crystallize and
glue particles of sediments
together
• Whole process: millions of years
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0604/es
0604page01.cfm?chapter_no=visualization
Types of Sedimentary Rocks
• Clastic rocks
• Organic rocks
• Chemical rocks
Clastic Rocks
• Forms when rock fragments are
squeezed together
• Grouped by size of fragments &
of which they are made
• Ex. shale, sandstone,
conglomerate and breccia
Shale
• Forms from
tiny particles
of clay
• Thin, flat
layers
Sandstone
• Forms from sand
Contains holes- can
absorb water
Conglomerate & Breccia
• Mixture of rock
fragments of
different sizes
Organic Rocks
• Remains of plants & animals are
deposited in layers
• Coal and limestone
Coal
• From remains of swampy plants
Limestone
• From hard shells of living things
• Ex. chalk
Chemical Rocks
• Forms when minerals that are
dissolved in a solution crystallize
(ex. rock salt)
Metamorphic Rocks
What is a metamorphic rock?
• A rock that has changed its form
• Can change igneous,
sedimentary, or other
metamorphic rocks
How do metamorphic rocks form?
• Heat and pressure beneath Earth’s
surface change rock
• Its appearance, texture, crystal
structure, and mineral content
change
Formation of Metamorphic Rocks
1. Earth’s plates push rock down
toward mantle- HOT!
2. Magma also heats the rock
3. The deeper the rock is buried…the
greater the pressure
4. Pressure and heat change minerals
Formation of Metamorphic Rocks
Granite to Gneiss
GRANITE
Gneissic granite –
separation of dark
& light minerals is
just beginning
Well banded gneiss
Classifying Metamorphic Rocks
• Classify rocks by arrangement of
grains that make up the rock
• Two types: foliated and
nonfoliated
Foliated Rock
• Grains arranged in parallel layers
• Can split apart along the bands
Shale to Slate
Shale
Slate
Nonfoliated Rock
• Mineral grains are arranged randomly
• Do not split into layers
Marble
Sandstone to Quartzite
Uses of Metamorphic rocks
• Slate and marble- most useful
metamorphic rocks
• Marbles- buildings and statues
• Slate- flooring, roofing,
chalkboards