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The Rock Cycle
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THE ROCK CYCLE
• Rocks are constantly being formed, worn
down and then formed again. This is
known as the Rock Cycle
• It takes thousands and million of
years for rocks to change
THE ROCK CYCLE
• http://www.classzone.com/books/earth_scienc
e/terc/content/investigations/es0602/es0602pa
ge02.cfm
TYPES OF ROCK
• Rocks are divided into 3 Types.
• They are classified by how they were
formed:
• IGNEOUS
• SEDIMENTARY
• METAMORPHIC
IGNEOUS ROCK
• Igneous rocks form when
molten rock cools and
becomes solid. Molten
rock is called magma
when it is below the
Earth’s surface and lava
when it is above.Igneous
rocks are divided into two
groups, based on where
the rock forms.
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IGNEOUS ROCK
• Igneous rocks that form below the Earth’s
surface are called intrusive igneous rocks (or
plutonic). They form when magma enters an
underground chamber, cools very slowly, and
forms rocks full of large crystals
• Igneous rocks that form above the Earth’s
surface are called extrusive igneous rocks.
These rocks, also called volcanic rocks, form
when lava cools quickly at or above the Earth’s
surface.
5 KINDS OF
IGNEOUS ROCK
•
•
•
•
•
Granite
Diorite
Gabbro
Periodotite
Pegmatite
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SEDIMENTARY ROCK
• When rocks erode, they crumble - a little bit at
a time
• This erosion takes place because of rain,
freeze/thaw cycle, wind and running water
• Eventually most of the broken bits of the rock
end up in the streams & rivers that flow down
from the mountains.
• These little bits of rock & sand are called
sediments. When the water slows down
enough, these sediments settle to the bottom
of the lake or oceans they run into. Over
many years, layers of different rock bits settle
at the bottom of lakes and oceans.
SEDIMENTARY ROCK
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• Over time the layers
of sand and mud at
the bottom of lakes &
oceans turned into
rocks. These are
called sedimentary
rocks.
• Fossils of ancient living
things are preserved in
sedimentary rocks
SEDIMENTARY ROCK
• There are 6 main kinds of sedimentary
rocks
• Conglomerate
• Sandstone
• Shale
• Limestone
• Gypsum
• Breccia
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METAMORPHIC ROCK
• Metamorphic rocks are rocks that
have changed. Metamorphic rocks
were originally igneous or
sedimentary, but due to movement of
the earth's crust, were changed
METAMORPHIC ROCK
• When the earth's crust moves, it
causes rocks to get squeezed so
hard that the heat causes the rock to
change. Marble is an example of a
sedimentary or igneous rock that has
been changed into a metamorphic
rock.
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METAMORPHIC ROCK
• Rock foliation may occur. It is the result
of pressure and recrystallization when
rocks undergo metamorphosis. It is the
layering and parallel alignment of
flattened or directionally oriented mineral
crystals. Slate, phyllite, schist, and gneiss
are all metamorphic rocks with foliated
texture.
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• Metamorphic rocks are igneous or
sedimentary rocks that have been
transformed by great heat or pressure.
Slate
Schist
Gneiss
Marble
Quartzite
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WEATHERING & EROSION
Weathering is the mechanical and
chemical hammer that breaks down
and sculpts the rocks.
Erosion transports the fragments
away.
HOW WEATHERING
& EROSION OCCURS
• ･Acid Rain: chemicals in the air combine with
precipitation When it rains it dissolves certain
minerals sensitive to acid.
• ･Leaching by ground water: water soaks into the
soil, picks up chemicals This allows the water
to leach or dissolve rocks it comes in contact
with at bedrock.
• ･Wave action at the beach: the waves tumble
rocks Rocks get ground down by the sand
particles already on the beach, rocks smash
against each other & break.
HOW WEATHERING
& EROSION OCCURS
• Fast moving water: rocks get picked up &
carried when water runs swiftly By
bouncing along a river & smashing into
other rocks, the sharp edges get knocked
off.
• ･Glaciers: large sheets of ice pick up large
rocks, scrape bedrock Rocks tumble in
under-glacier rivers when glaciers melt.
• ･Precipitation / Floods: heavy rain can
cause floods which move & break rocks
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Broken glass is tumbled on the beach
and worn smooth by the action of the
waves
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Broken bits of shale tumble to the bottom of hills
and river banks. Then the are washed away and
tumbled by waves and water. When they are
deposited at the side of rivers and on the beach,
they are smooth. This is caused by erosion.
The Rock Cycle Diagram
• http://www.learner.org/interactives/rockcycle/diagr
am.html
Homework Assignment
• Complete the interactive lesson on
http://www.learner.org/interactives/rockcycle/ind
ex.html
Begin Introduction, Types of Rocks, How Rocks
Change, The Rock Cycle Diagram, Test Your
Skills - read and complete the quiz of each
section