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The Rock Cycle
Basics
The Rock Cycle is a group
of changes in which:
Igneous rock can
change into
sedimentary rock or into
metamorphic rock
Sedimentary rock can
change into
metamorphic rock or
into igneous rock.
Metamorphic rock can
change into igneous or
sedimentary rock.
Igneous Rock
Igneous rock is formed when magma cools and
makes crystals; deep in the Earth
Magma is a hot liquid made of melted minerals.
The minerals can form crystals when they cool.
When magma cools slowly , large crystals form or
when it cools quickly (often above ground), small
crystals form
Sedimentary Rock
Sedimentary rocks form at or near the
earth's surface at relatively low
temperatures and pressures primarily
by deposition by water, wind or ice
Metamorphic Rock
Metamorphic Rock is formed when rocky
material experiences intense heat and
pressure in the crust of the earth.
Heat and pressure do not change the
chemical makeup of the parent rocks but
they do change the mineral structure and
physical properties of those rocks.
Pause Here
Sediment
Sediment can either be:
Material eroded from rocks that is
carried by water, wind, or ice and
deposited elsewhere
Plutonic and Volcanic Rock
Volcanic rocks, a.k.a extrusive rocks or lava
rocks, crystallize when the magma reaches the
earth’s surface cooling quickly.
Plutonic or intrusive rocks crystallize within the
crust of the earth, and as a result plutonic rocks
cool at a much slower pace then volcanic rocks
Melting
Melting is the result of continued heating
Leads to production of magma and new
igneous rocks which are formed when the
magma cools.
Heat and Pressure
Metamorphic rocks trapped underground
are still subject to enormous heat from
rising magma, or heated water, and
pressure. Sometimes the heat can get so
intense the rocks actually melt.
Pressure comes from the incredible weight
of material surrounding the rock on all
sides.
Weathering
Weathering- The process in which rocks
are broken down by chemical and/or
physical mechanisms into smaller particles.
There are three types of weathering
Physical weathering
Chemical Weathering
Biological weathering
Erosion
Erosion is the wearing away of
exposed surfaces by agents such as
wind, moving water and ice.
Subduction
A rock that gets caught up in the subduction zone
may get dragged down with the oceanic plate.
As the rock gets dragged down, they undergo
metamorphism.
Some parts of the rocks get taken all the way down
to the mantle where they slowly mix with the rest of
the mantle. – this is the only way that rocks formed on
the continent get recycled with the mantle.
Compaction
The result of this
pressure is a
compaction of the
sediment
Because of
compaction, rocks
becomes more
dense.
Cementation
Most sediments are
deposited in water
containing dissolved
minerals.
The water flows through
the sediment and some of
these minerals precipitate
on the grain surfaces.
With time, this
intergranular material
effectively glues the
sediment together into a
cohesive solid- a
sedimentary rock.
Uplifting
Because certain rocks are created under the
Earth’s surface A process called uplifting
occurs through orogeny and volcanic
process, which then bring rocks to the
surface. The rock is eventually becomes
recycled again.
Transportation
This process occurs when the particles
created by weathering are carried by ice, air,
or water to a region of lower energy known
as a sedimentary basin.
Decomposition
Decomposition takes place when a lowering
of hydraulic energy, organic biochemical
activity, or chemical changes occur.
Crystallization
When hot conditions that caused magma to melt will cool, either
because the source of heat subsides or the magma moves into cooler
regions of the Earth.
When it gets cool enough the minerals that will make up the rock
begin to crystallize and form an intergrown mass of crystals.
If the crystals begin to form deep in the Earth where it is relatively
warm the magma cools slowly allowing the crystals to grow relatively
large.
If the magma reaches the surface, the lava cools quickly and the
crystals do not have time to grow very large.
If the crystals cannot grow at all and volcanic glass is formed.
Earthquakes
An earthquake is the shaking of
the Earth’s surface caused by
the rapid movement of the
Earth’s rocky outer layer.
Earthquakes occur when energy
stored within the Earth, usually
in the form of strain in rocks,
suddenly releases.
This energy is transmitted to the
surface of the Earth by
earthquake waves or seismic
tremors.
Most earthquakes are
caused by the sudden slip
along geologic faults
because of movement of
the Earth’s tectonic plates.
The rocky tectonic plates
move very slowly, floating
on top of a weaker rocky
layer.
As the plates collide with
each other or slide past
each other, pressure builds
up within the rocky crust.
Earthquakes occur when
pressure within the crust
increases slowly over
hundreds of years and
finally exceeds the
strength of the rocks.
Plates
The Earth is made up of plates.
There are 2 kinds of plates:
(1) Continental Plate
(2) Oceanic Plate
These plates move past each other and occasionally slip above or
below one another.
As the plate sinks lower and lower beneath another plate, the heat and
pressure it gives off causes the rock to melt.  volcano
Sometimes if one plate doesn’t slide underneath another, the the
plates will collide and push each other upward.  mountains
When this happens, they melt and recrystallize due to the heat and
pressure put on them.
Continental Plate
Continental crust is much older, thicker and less dense than
oceanic crust.
The thinnest continental crust, between plates that are moving
apart, is about 15 km (about 9 mi) thick.
In other places, such as mountain ranges, the crust may be as
much as 75 km (47 mi) thick.
Near the surface, it is composed of rocks that are felsic (made
up of minerals including feldspar and silica).
Deeper in the continental crust, the composition is mafic
(made of magnesium, iron, and other minerals).
Oceanic Plate
Oceanic crust makes up 60 percent of the earth’s solid surface.
Oceanic crust is thin and dense. Oceanic crust averages between 5 and 10 km
(between 3 and 6 mi) thick.
It is composed of a top layer of sediment, a middle layer of rock called basalt, and
a bottom layer of rock called gabbro.
Basalt and gabbro are dark-colored igneous, or volcanic, rocks.
It is constantly produced at the bottom of the oceans in places called mid-ocean
ridges—undersea volcanic mountain chains formed at plate boundaries where there
is a build-up of ocean crust.
This production of crust does not increase the physical size of the earth, so the
material produced at mid-ocean ridges must be recycled, or consumed, somewhere
else.
Oceanic crust is continually recycled so that its age is not greater than 200 million
years.
Plate collision where the oceanic plate (crust)
will slide beneath the continental plate (crust)
because it is more dense than the continental
plate.
A plate collision where the continental plates
(crusts) collide. Thus, they have to go up.
Bibliography
“The Rock Cycle.” www.science.ubc.com.ca. 8 Aug. 1997. The University of British Columbia.
19 Sep. 2003 http://www.science.ca/~geo/202/rock_cycle/rockcycle.htm/
“The Rock Cycle.” www.rocksandminerals.com. 21 Feb. 2003. SciLinks. 19 Sep. 2003.
http://www.rocksandminerals.com/rockcycle.htm.
“What’s A “Rock Cycle?” www.priweb.org. Paleontological Research Institution. 19 Sep. 2003.
http://www.priweb.org/ed/pgws/geology/geology1.html.
Plate Tectonics. www.encarta.msn.com. 1993-2003. Encyclopedia Article from Encarta. 19
Spe. 2003
http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761554623&pn=1&para=29#p2
9.
“The Rock Cycle” http://www.shore.ctc.edu/geology/ProcessesProducts.html 19 Sep. 2003
Credits
La Canada High School
AP Environmental Science
PD. 5/ Ewoldsen
Sarah Dowling
Rupa Kamboj
Joy Kim
Tony Tavlian
Jean Young