Download The Rock Cycle

The Rock Cycle
Fun with rocks?
What is this “rock cycle”?
The rock cycle is a process that
turns one type of rock into another
type of rock.
Tell me why I should care!
• As scientists, we require knowledge…we need
to understand the world around us!
• Knowing where certain types of rocks are can
tell us where to find oil and natural gas
deposits.
• Oh yeah…the information you learn here really
will help you understand what you will see in
high school and you may just discover you like
learning about this stuff.
So…let’s get started.
But with a cycle, how do you know
where to start?
Let’s start with the different
types of rocks
Igneous rocks
• The word “igneous” refers to anything
relating to fire.
• An igneous rock is one that is made
when magma cools and hardens.
• Slow cooling allows crystals to form.
• Rapid cooling can result in no crystal
formation.
Igneous rock w/crystals
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Igneous rock w/o crystals
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Sedimentary rocks
• These are rocks that are formed when
particles of other rocks and sometimes
particles of once living things
accumulate in the same area and are
cemented together by minerals
deposited between the grains.
Sedimentary rock (sandstone)
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Sedimentary rock (halite)
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Metamorphic rocks
• These are rocks that have been
changed by heat and pressure, usually
below the earth’s surface.
• This heat and pressure changes the
texture and the chemical composition of
the rock.
Metamorphic rock (gneiss)
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Metamorphic rock (slate)
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And you thought rocks weren’t
exciting…shame on you.
How do these rocks
become…well…rocks?
Igneous rocks
• Recall that igneous rocks are made
from molten rock material (magma/lava)
that cools and hardens.
• Magma can be ejected from a volcano
or some other fracture in the earth’s
surface (we call these EXTRUSIVE)
• OR it can cool and harden below the
ground (we call these INTRUSIVE).
Imagine an igneous rock at
the surface…hmmmm.
• You could be walking along the side of a
volcano and kick a rock into the lava and
watch it melt…but the rock cycle doesn’t need
our help.
• On the surface of the earth, this rock is
exposed to outside forces such as wind and
water.
• These things break the rock down, but it
takes a LONG time…this process is known as
weathering.
Weathering
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• The particles of these rocks
are now somewhere else
because of the process of
transportation…the
particles get dropped off or
deposited with other
particles from other rocks
where they accumulate, get
compacted, and eventually
cement together.
Physical or Mechanical
Weathering
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• This is the disintegration of rock through direct
contact with the atmosphere.This usually involves
action by wind or water but can include heat,
pressure, and ice! This doesn’t involve rock
movement…the rock sits there and these things
happen to it. Erosion, on the other hand, involves the
movement of rocks.
Chemical Weathering
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• Chemical weathering changes the composition of
rocks, changing them when things like water or
oxygen interact with minerals to create various
chemical reactions. Oxidation is a common form of
chemical weathering often causing rocks containing
iron (Fe) to appear as if they have rusted.
Transportation
• The movement of particles
from one place to another.
This movement is the result
of wind, water, and gravity.
Deposition
• The process of “dropping off”
previously weathered or eroded
sediment particles. This
happens when the forces that
carry the sediment particles
aren’t able to carry them any
farther.
Sedimentation
• The process of particles in
suspension (such as in the
water) to settle out and come to
rest. These particles
accumulate and build up over
time.
Compaction and Lithification
• Sediment particles that are deposited
and settle out of suspension have
spaces between the particles that are
often filled with water…when enough of
these particles come to rest on top of
one another, their mass pushes the
water out, leaving the minerals behind
to bind the sediments together.
Seriously…are we done yet?
Sort of.
Let’s take a look at the entire cycle in a diagram.
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A diagram doesn’t really do it justice…but hopefully it
gives you a snapshot of the cycle.
There is sooooo much more to
the rock cycle…but these are
the pieces I believe give us the
best opportunity to fully
understand it.