Download The Rock Cycle

The Rock Cycle
•
• Types of Rocks
Forces that change rocks
• Weathering
• Erosion
• Deposition
• Heat and Pressure
Types of Rocks: IGNEOUS
Igneous rocks are “made by fire” because they are
formed from magma (molten rock) or volcanic
activity.
Igneous rocks include quartz, granite, obsidian,
geodes, ash, pumice, lava, feldspar, mica, silica,
and many minerals and crystals.
If the magma reaches the surface of the earth, it
can cool quickly, leaving little time for crystals to
grow. Magma that cools under the surface takes
longer to cool, and the crystals have time to
grow bigger. Large granite domes such as
Enchanted Rock (TX) and Half Dome (Yosemite)
were once magma “bulges” underground.
Igneous Rock Review
• Intrusive Igneous:
• Extrusive Igneous:
• Magma that cools under • Magma at the earth’s
the earth’s surface,
surface is called lava
underground
• The more silica in the
magma, the more
explosive the eruption
• Granite (same silica
content as obsidian)
• Gabbro (silica- poor)
• Obsidian, rhyolite
(silica- rich, like granite)
• Basalt (gentle flow of
lava, small grains)
Write what you learned about
igneous rocks
• What is magma?
• What is the difference
between magma and
lava?
• What kinds of rocks
are formed from
magma underground? • What kinds of rocks
are formed from lava?
• What other things did
you learn?
Types of Rocks: Sedimentary
• Sedimentary Rocks are made from sediments,
or small pieces of other types of rocks which
have been broken down (weathered,) carried
away (eroded,) and deposited in other places
on the earth’s surface.
• Sedimentary rocks usually show layers (as in
sandstone or shale) or small pieces that are
cemented together to form larger rocks (such
as conglomerates or aggregates.) Other
sedimentary rocks are formed by buried
decaying organisms such as plants and animals.
Types of Sedimentary Rocks
• Clastic Rocks: “stuck
together” rocks
• Sandstone (made from
sand grains)
• Siltstone/ mudstone
(made from mud or silt
stuck together)
• Shale (made from tiny
clay particles)
• Conglomerates (pebbles
and sand cemented by
minerals)
• Chemical Rocks: made
from minerals after the
water that carried them
evaporates)
• Rock Salt (Halite)
• Gypsum
• Limestone (from
evaporated seas/ lakes)
• Chert
More Sedimentary Rocks
• Organic Rocks:
formed from the
remains of plants and
animals
• Coal: see text p. E5859
• Chalk (from tiny sea
creatures)
• Limestone (from sea
animals with shells)
• Fossils: from plants
or animals buried in
layers of sediments,
then replaced by
minerals (text p. E7477)
• Mold: imprint, hollow
“cup.” “A mold can
‘hold’.”
• Cast: the actual 3-D
object turned to stone
Review
Sedimentary
Rocks
Clastic:
“stuck together”
Chemical:
“Mineral deposits”
Organic:
Decayed plants/
Animals
Write what you learned about
sedimentary rocks
• How are sedimentary rocks formed? Include
words such as:
–
–
–
–
–
–
–
–
Erosion
Deposits
Sediments
Cementing
Pressure
Layers
Evaporation
Dissolved
METAMORPHIC ROCKS
• The word “metamorphic” means “to
change form.”
• Metamorphic rocks begin as some other
type of rock (igneous or sedimentary) and
then change.
• Examples:
– Shale (sedimentary)
Slate (metamor.)
– Granite (igneous)
Gneiss (metamor.)
– Limestone
(changes to) marble
Rocks Can Change
• Changes are seen in the
texture (size of grains)
and/ or composition
(mineral make-up) of the
rock.
• Contact metamorphism
(see Heat)
• Regional Metamorphism
(see Pressure)
• Burial Metamorphism
(Heat & Pressure are
lower)
• Causes of change are:
– Heat (contact with nearby
magma changes minerals
and grain sizes)
– Pressure (from weight of
rocks on top causes grains
to line up in the same
direction = banded rocks)
– Chemicals (from magma’s
liquids or gases change
minerals)
Fossil Fuels
Plants & Animals contain carbon
and hydrogen. They undergo
changes when they die and
are quickly buried under other
sediments.
Bacteria, pressure Swamp or bog plants More heat & pressure
from more sediments, decay and form peat. form coal, which is a
and increased heat More heat & pressure rock that burns as
change organisms into
form lignite
fuel.
Fossil Fuels.
(a sedimentary rock.)
Fossil Fuels
• OIL AND GAS ARE FORMED FROM
REMAINS OF OCEAN PLANTS AND
ANIMALS THAT WERE BURIED BY
SEDIMENTS.
• OVER LONG PERIODS OF TIME,
BACTERIA, HEAT, AND PRESSURE
CHANGED THE ORGANISMS TO OIL
AND GAS.
Write what you know about
fossil fuels
• Tell what specific materials make fossil
fuels.
• Name as many fossil fuels as you can.
• Are these sources of energy renewable?
• What forces are necessary to make fossil
fuels? Explain.
• Does it take a short/ long time to make
fossil fuels? Explain.
• What living organisms help change the
decayed materials into fossil fuels?
THE ROCK CYCLE
• Forces that break
down:
• Weathering and Erosion
– Roots break rocks.
– Freezing and heating
make cracks.
– Glaciers scour, polish,
move, or grind rocks.
– Wind (scouring, erosion)
– Water (erosion)
– Dissolving
• Forces that build up:
• Deposition of more
sediments over time
• Rising magma forms
new rocks under the
earth’s surface.
• Lava flows and volcanic
eruptions bring more
rock material to the
surface of the earth
(ash, lava, obsidian,
basalt, etc.)
HEAT AND
PRESSURE
DEPOSITION
ROCK CYCLE
MELTING
WEATHERING
COOLING
ROCK CYCLE
COOLING
• Magma cools to form granite,
gabbros, and minerals
• “Lava” (extrusive magma that
reaches the surface of the earth)
cools to form obsidian (volcanic
glass,) pumice, basalt, lava
rocks
WEATHERING
• All rocks can be broken down or
“weathered.”
• The pieces of rock can be huge blocks or
slabs that break off from cliffs or boulders
that are moved by glaciers.
• Rocks and minerals may be ground up
into grains of sand.
• Rocks may be tumbled in rivers against
other rocks to form pebbles.
DEPOSITION
• Broken pieces of rock are carried and
deposited (set down) in other places by:
– Wind (dust storms)
– Water (wave action, floods, mudslides, rivers,
rain runoff)
– Evaporation leaves sediments behind
(minerals in caves or lakebeds, or in layers of
sediments)
MELTING
• All types of rocks can melt and become
magma again:
– Igneous
– Sedimentary
– Metamorphic
• The cycle begins again and continues to
change rocks as time goes on.
Write your explanation of
the rock cycle
• Write several paragraphs to explain the
steps of the rock cycle. Write a short
explanation for each word:
• Melting
• Cooling
• Weathering
• Deposition
• Heat and Pressure