Download The Rock Cycle

The Rock Cycle
What’s a rock?
Mixture of minerals, mineraloids, glass,
or organic matter.
There are three main types of rocks
Sedimentary
 Metamorphic
 igneous

Sedimentary Rocks
Origins
Form when sediments become pressed or
cemented together or precipitate out of a
solution.
Sediments = loose materials (rock fragments,
mineral grains and bits of plant and animal
remains that have been moved by wind,
water, ice or gravity)
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Sediments come from rocks that are weathered or
eroded
Weathering = process that breaks rocks into
smaller pieces (mechanical and chemical)
Compaction
Erosion moves sediments & deposits
them
Sediment builds up by layers
Top layers push down on bottom layers
Cementation
Large sediments (sand, pebbles) won’t stick
together with just pressure
Water soaks through soil & rock
Minerals are dissolved – these minerals are
natural cements
Water + minerals moves thru sediment and
the minerals are deposited and sediments
stick together.
Precipitation
Rocks form when minerals precipitate (a solid
forms from a solution) or when a solution
evaporates and leaves a solid behind.
Solution
Remaining
liquid
Precipitate
Classify Sedimentary
Rocks
Chemical sedimentary rocks

Form when minerals precipitate from a
solution or when a solution evaporates
Limestone = calcite which grows together along
with minerals and sediments
 Rock salt – used in mfg. of glass, paper, soap
and dairy products – also table salt

Examples of Chemical
Sedimentary Rocks
Limestone
Rock salt
Classify Sedimentary
Rocks
Detrital = Latin word means to wear
away
Made of broken fragments of other rocks
 Have clastic texture (clastic = broken)
 Conglomerate forms from large fragments
 Sandstone forms from small particles
 Shale requires no cementation - clay-sized
particles are compacted under pressure

Examples of Detrital
Sedimentary Rocks
sandstone
Shale
conglomerate
Organic Sedimentary
Rocks
Rocks form from the remains of once
living organisms
Chalk
 Coal

Metamorphic Rocks
Origins
Formed by temperature and pressure
Go through composition changes
Metamorphic Rocks
When heat and pressure aren’t enough
to form magma and melting does not
occur, metamorphic rocks can form
Metamorphic rocks can form from
changes in igneous, sedimentary or
other metamorphic rocks.
Classified in two ways: foliated &
nonfoliated
Foliated Rocks
When grains flatten and line up in
parallel bands
This happens because there are usually
many different types of minerals in the
parent rock.
Slate
Gneiss
Nonfoliated Rocks
No bands in rocks
This happens because the parent rock
is usually made of only one type of
mineral.
Marble
Igneous Rocks
Origins
Molten material from a volcano or deep
inside the earth cools; forms igneous
rocks
Magma (info)
It forms at high temperatures (1400oC.) below
Earth’s surface (60-200 km)
The heat flows up from Earth’s interior
Magma is less dense than solid rock around it
Magma is forced up to Earth’s surface
Magma that reaches Earth’s surface and
flows from volcanoes is lava
Think of it like this
Magma (Summary)
Hot stuff
Inside earth
Less dense than solid rock
Forced up to the surface
When on surface is called lava
Igneous Rocks
A rock that is formed when molten material from
a volcano or deep within the Earth cools.
Classified by how they cool

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Intrusive
Extrusive
Also classified further by magma type
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Basaltic
Granitic
Andesitic
Intrusive Rocks
Magma = melted minerals
Rocks form as these mineral grains cool
and grow together
Formed below Earth’s surface
Have large mineral grains
Andesite
Extrusive rocks
Lava cools quickly at Earth’s surface due to
exposure from air and water
No large mineral grains
Pumice, obsidian and scoria cool quickly so
no mineral grains formed. (In pumice and
scoria air became trapped in gooey lava and
left holes)
The rock cycle
Shows how rocks are constantly
changed from one form to another
Has no beginning and has no end