The document discusses the rock cycle, which describes how rocks are continuously changing forms over geological time through igneous, sedimentary, and metamorphic processes. Igneous rocks form from the cooling of magma either below ground as plutonic rocks or above ground as volcanic rocks. Sedimentary rocks form from the lithification of sediments eroded from other rocks. Metamorphic rocks form from changes to existing rocks through heat, pressure, and fluids in the Earth. The rock cycle demonstrates how these three main rock groups are interrelated and how matter is recycled over time through weathering, erosion, deposition, and tectonic activity.

1. The Rock Cycle
An Exploration of the World Under Your
Feet

2. What is a “Rock”?
• Rock: is a fairly general term that refers to any
solidified mixture of inorganic or fossilized organic
materials.
– There are a multitude of extremely diverse rock
types that can be differentiated and classified
based upon their elemental composition, physical
properties, and formation mechanism.
• Mineral: inorganic solid with a specific internal
structure and a definite chemical composition.
– Minerals are the basic building blocks of rock.
– Almost all minerals contain some combination of
the following elements:
2
• Oxygen - O
• Silicon - Si
• Magnesium - Mg
• Iron - Fe
• Aluminum - Al
• Calcium - Ca

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3 Major Rock Types
• Igneous
– Formed from the solidification of molten
rock (magmaor lava).
• Sedimentary
– Formed at the Earth’s surface from the
accumulation and cementation of
fragmented pieces of older rock
produced by weathering.
• Metamorphic
– Rocks that have undergone physical
changes as a result of exposure to
extreme pressure, temperature and
fluids.

4. The Rock Cycle
• Law of Conservation of Matter: Matter cannot be created
or destroyed it can only change forms.
• This fundamental law of the universe applies to the
chemical elements that make up the earths rock.
• Particular rock formations are created and destroyed many
times over geologic timescales but the chemical material
itself is recycled over and over again through the rock
cycle.
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6. Igneous Rocks
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7. Types of Igneous Rock
• Igneous (ignis= fire)
– Formed from the solidification of molten rock
(magma or lava).
• Magma: is molten rock below the surface of the earth.
• Lava: is molten rock that has been extruded on to the
surface of the earth.
– Igneous Rocks are generally classified based on
where in the earth crystallization takes place.
• Plutonic (Intrusive): Magma slowly cools and crystallizes
below the earths surface.
– Since the cooling process is very slow intrusive igneous rocks have
very large crystals (coarse grained).
• Volcanic (Extrusion): Lava cools quickly at the surface of
the earth.
– Since the cooling process is very fast extrusive igneous rocks have
very small crystals (fine grained). 7

8. Igneous Classification:
Texture
Volcanic Glass:
Extrusive igneous rock
formed when lava comes
in contact with water and
cools instantly. Appears
glass-like.
Example: Obsidian
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9. Igneous Classification:
Texture
Aphanitic: Typically form from lava
which crystallizes rapidly on or near
the Earth’s surface.
• Because extrusive rocks make
contact with the atmosphere they
cool quickly, so the minerals do
not have time to form large
crystals.
• The individual crystals in an
aphanitic igneous rock are not
distinguishable to the naked
eye.
• Example: Basalt 9

10. Igneous Classification:
Texture
• Phaneritic: (phaner = visible)
textures are typical of intrusive
igneous rocks, these rocks
crystallized slowly below the
Earth's surface.
• As a magma cools slowly
the minerals have time to grow
and form large crystals.
• The minerals in a phaneritic
igneous rock are sufficiently large
to see each individual crystal with
the naked eye
• Example: Fine Grain Granite 10

11. Igneous Classification:
Texture
• Pegmatitic: Texture that occurs
during very slow magma cooling
when some minerals may grow
so large that they become
massive.
• Crystal size ranges from a few
centimeters to several meters.
• Example: Large Grain Granite
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12. Igneous Classification:
Composition
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13. Igneous Classification:
Composition
• Felsic Rocks: Are those that are light in
color and are mostly made up of
feldspars and silicates. Low Density.
• Intermediate Rocks: fall somewhere in
between being Felsic and Mafic.
Intermediate Density.
• Mafic Rocks: Are darker colored and
are mostly made up of magnesium and
iron.
– Ultramafic Rocks: Very dark colored. 13

14. Fig. 2.9
MAGMA

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MAGMA
Crystallization
IGNEOUS

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MAGMA
IGNEOUS
Plutonic
Crystallization

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MAGMA
Volcanic
IGNEOUS
Plutonic
Crystallization

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MAGMA
Volcanic
IGNEOUS
Plutonic
Uplift
Crystallization
Weathering

19. Weathering, Transport, and
Deposition 19

20. Weathering, Erosion, and Deposition
Weathering – the breakdown of rocks into smaller
pieces, called sediments.
Transport (Erosion)– the process where the sediments
are carried by wind, gravity, glaciers, man, and running
water.
Deposition – the process whereby these sediments are
released by their transporting agents (dropped).
Weathering breaks down the rocks, erosion moves the particles,
and deposition drops the sediments in another location.

21. Types of Weathering
• There are two main types of weathering:
– Physical Weathering: the breakdown of rocks
and minerals into smaller pieces without a change
in chemical composition.
– Chemical Weathering: the breakdown of rocks
and minerals into smaller pieces by chemical
action. The rocks breaks down at the same time
as it changes chemical composition. The end
result is different from the original rock.

22. Types of Weathering
22

23. Frost Wedging: rock breakdown
caused by expansion of ice in
cracks and joints.
- Water expands when it freezes

24. Exfoliation: As previously buried rock
formations are exposed they experience a
decrease in confining pressure causing them
to expand and fall off in parallel sheets.

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26. Plant and Animal Activity
• Lichens and mosses grow on
rocks.
– They wedge their tiny roots
into spores and crevices.
– When the roots grow, the
rock splits.
• Larger trees and shrubs may
grow in the cracks of boulders.
• Ants, earthworms, rabbits,
woodchucks, and other animals
dig holes in the soil.
– These holes allow air and
water to reach the bedrock
and weather it.
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27. There Are 3 Types of Chemical Weathering:
Oxidation– oxygen combines with the elements
in the rock and it reacts. This the scientific name
for rust.
Hydration– water can dissolve away many earth
materials, including certain rocks.
Carbonation– carbon dioxide
dissolves in water to form carbonic
acid. This makes acid rain which
chemically weathers (dissolves)
rocks. Other acids also combine with
water to make acid rain.

28. Karst Topography
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29. 2.Particle Size – Larger particles weather slower and smaller
particles weather at a faster rate.
There are 4 factors that effect the rate of weathering:
1.Surface Area (exposure) - Exposing more surface area will
increase the rate of weathering.
3.Chemical Composition (what a rock is made of) – Certain rocks
and minerals are naturally weaker than others, while others are more
resistant (stronger).
4. Climate – Warmer, moister climates have the most weathering.
Heat & Water speed up all chemical reactions. This is the most
important factor in weathering.

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MAGMA
Volcanic
IGNEOUS
Plutonic
SEDIMENT
Uplift
Crystallization
Weathering SEDIMENT

31. Transport and Deposition
• Sediments are transported away and
deposited in other locations.
• These depositional environments are often
layered or stratified.
– Older sediments at the bottom
– Newer sediments on top
• One can deduce the transport mechanism
based upon:
– Grain Size
– Sorting
– Roundness 31

32. Grain Size
• Based on the
fundamental idea that as
the amount of weathering
increases a rock will
break into smaller and
smaller pieces.
• The grain size a
sediment tells you how
much weathering it has
undergone.
– Also tells you the strength
of the transport process.
• Wentworth Scale
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33. Roundness
As weathering increases a sediments well
defined sharp edges wear away
(angularity decreases) and the rock
becomes more rounded
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36. Sorting
• Sorting describes the distribution of grain
size of sediments.
• Very poorly sorted indicates that the sediment
sizes are mixed (large variance)
• Well sorted indicates that the sediment sizes
are similar (low variance).
• The degree of sorting may also indicate the
energy, rate, and/or duration of deposition, as
well as the transport process responsible for
laying down the sediment.
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38. You can identify which agent of erosion transported each
sediment by looking at a few characteristics:
Running Water – sediments that have been transported through
running water appear rounded and smooth and are deposited in
sorted piles.
Glaciers – sediments that have been transported by glaciers appear
scratched, grooved, and are deposited in completely unsorted
piles, because they were dropped during melting. Also, boulders
can only be transported by glaciers.
Wind - sediments that have been transported by wind are appear
pitted (random holes) and frosted (glazed look) and are deposited
in sorted piles. Only very small particles can be transported by
wind.
Gravity – sediments that are transported by gravity are found in
piles at the bottom of cliffs or steep slopes. They appear angular
and unsorted.

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MAGMA
Volcanic
IGNEOUS
Plutonic
SEDIMENT
SEDIMENTARY
Uplift
Crystallization
Weathering
Erosion
Transport
Deposition

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MAGMA
Volcanic
IGNEOUS
Plutonic
SEDIMENT
SEDIMENTARY
Uplift
Crystallization
Weathering
Erosion
Transport
Deposition

41. Classifying Sedimentary
Rocks
• Sedimentary rocks are classified by their
composition and by the manner in which
they formed.
• The three types of sedimentary rocks are
– Detrital: Sedimentary rocks that are made from
the broken fragments of other rocks.
– Chemical (Evaporite): Mineral crystal formed
when water evaporates and leaves behind any
dissolved (chemically weathered) minerals.
– Organic: Sediment formed from the remains of
dead plants and animals.

42. Compaction and
Cementation Forms Detrital
Sedimentary Rocks
• Where sediments are deposited, layer upon layer builds up.
• Pressure from the upper layers pushes down on the lower
layers.
• If the sediments are small, they can stick together and form
solid rock. This process is called compaction.
• If sediments are large, like sand and pebbles, pressure
alone can’t make then stick together
– Large sediments have to be cemented together.
• As water moves through soil and rock, it picks up materials
released from minerals during weathering.
• The resulting solution of water and dissolved materials moves
through open spaces between sediments cementing them
together.

43. Detrital Sedimentary Rocks
43

44. Chemical Sedimentary Rocks
(Evaporites)
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45. Geodes
Formed when air pockets in rock fills with water forming
evaporite crystals.
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46. • Form from Biogenous
Ooze
– >30% of debris from planktonic
organisms
– Calcareous oozes (CaCO3)
• Shells of foraminifera
(zooplankton) and
coccolithophorids
(phytoplankton).
• Accumulate on seafloor.
• Forms hard limestone under
pressure
Biologic Sedimentary Rocks

47. Deep-sea sedimentation
processes

48. Biologic Sedimentary Rocks
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MAGMA
Volcanic
IGNEOUS
Plutonic
SEDIMENT
SEDIMENTARY
METAMORPHIC
Uplift
Burial
Increased P&T
Crystallization
Weathering
Erosion
Transport
Deposition

50. Metamorphic Rocks
• Metamorphic rocks arise from the
transformation of existing rock types, in a
process called metamorphismwhich means
"change in form".
• The original rock is subjected to heat
(temperatures> 150 °C) and pressure (>1500
bars)causing profound physical and/or
chemical change.
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51. Types of Metamorphism
• Contact Metamorphism: Rock that
comes in close contact with magma and
undergoes metamorphism as a result of
the extreme temperature.
• Regional Metamorphism: A large
volume of rock is buried in the crust and
exposed to high temperature and
pressure.
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52. Gem Stones
• Many precious minerals
form at metamorphic
zones.
• Minerals with low
melting points liquefy,
while those with higher
melting points remain
solid.
– These liquefied minerals
accumulate in voids,
solidify, and become
precious minerals.
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MAGMA
Volcanic
IGNEOUS
Plutonic
SEDIMENT
SEDIMENTARY
METAMORPHIC
Uplift
Burial
Increased P&T
Melting
Crystallization
Weathering
Erosion
Transport
DepositionCan you see
any shortcuts?

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MAGMA
Volcanic
IGNEOUS
Plutonic
SEDIMENT
SEDIMENTARY
METAMORPHIC
Uplift
Burial
Increased P&T
Melting
Crystallization
Weathering
Erosion
Transport
Deposition

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57. • The rock cycle
demonstrates the
relationships among the
three major rock groups
• It is powered by the
interior heat of the Earth
• It involves processes on
the Earth’s surface as
well as the Earth’s interior
• It connects the
“hydrologic cycle” with the
“tectonic cycle”.
In Conclusion…

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MAGMA
Volcanic
IGNEOUS
Plutonic
SEDIMENT
SEDIMENTARY
METAMORPHIC
Uplift
Burial
Increased P&T
Melting
Crystallization
Weathering
Erosion
Transport
Deposition

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Major Rock Groups
• Igneous
– Formed from the solidification of molten rock
(magmaor lava).
– Plutonic (intrusive):slow cooling and crystallization
– Volcanic (extrusion): quick cooling at the surface
• Sedimentary
– Formed at the Earth’s surface from the accumulation
and cementation of fragmented pieces of older rock
produced by weathering.
– Clastic (Mineral Fragments or grains, clays)
– Chemical (crystalline chemical/biochemical
precipitates)
• Metamorphic
– Rocks that have undergone physical changes as a

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