2. DEFINITION
Rock Cycle
• Shows the origin of the 3 basic rock types and illustrates the
different geological processes that transform one rock type
into another
• Is the natural process in which rocks transform from one rock
type into another rock type over time, a type of natural
recycling.
4. IGNEOUS ROCKS
• Ignus – “fire”
• Forms as magma cools and solidifies
• Intrusive
• Rocks that cool inside the earth
• Plutonic (Pluto – The Roman god of the Underworld)
• Ex. Granite
• Extrusive
• Rocks that cool on the surface of the earth
• Volcanic (Vulcan – The Roman god of Fire)
• Ex. Basalt
5. INTRUSIONS
• An intrusion is liquid rock that forms under Earth's surface.
• Batholith
• a large irregular discordant intrusion
• Laccolith
• concordant body with roughly flat base
and convex top, usually with a feeder pipe below
• Stock
• a smaller irregular discordant intrusion
• Sill
• a relatively thin tabular concordant body intruded along
bedding planes
• Dike
• a relatively narrow tabular discordant body, often nearly
vertical
6. EXTRUSIONS
• An extrusion is liquid rock that forms above Earth's surface.
• Volcanoes
• A volcano is an opening, or rupture, in a planet's surface or
crust, which allows hot magma, volcanic ash and gases to
escape from below the surface.
• Lava Plateau
• Lava plateaus are formed by highly fluid basaltic lava
during numerous successive eruptions through numerous
vents without violent explosions.
• Rift Valley
• A rift valley is a linear-shaped lowland between highlands
or mountain ranges created by the action of a
geologic rift or fault.
7. THE PROCESS
Crystallization
- As magma cools, the random movement of ions
slow; and then the ions rearrange themselves into an orderly
pattern.
The rate of cooling influences the size of the forming
crystals.
- Slow cooling results in the formation of large
crystals
- Rapid cooling results in the formation of a solid
mass with small interlocking crystals.
8. CLASSIFYING
Texture
- The overall appearance of an igneous rock is based on the
size and arrangement of its interlocking crystal structure.
- Phaneritic
- Coarse grained. Magma solidifies under the earth’s
surface as a result the rocks have a large crystalline
structure. Ex. Granite.
- Aphanitic
- Fine grained . Magma solidifies quickly on the surface of
the earth. The result is a solid mass with crystals too small
to be seen by the unaided eye.
9. CLASSIFYING
- Porphyritic
- Magma already contains large crystals then is ejected and
the remaining magma cools quickly. The result is in
appearance of a large crystal embedded in a matrix of
small crystals.
- Glassy
- Ions in magma does not have sufficient time to unite and
create a crystalline structure.
13. SEDIMENTARY
• “sedimentum”- settling
• Sediments – unconsolidated particles created from weathering
and erosion of rocks. Weathering can be mechanical of
chemical in origin.
• Sedimentary rocks – rocks formed from the weathering of
pre-existing rocks that are transported, deposited and lithified.
• Lithification – process that transforms sediments into solid
sedimentary rock.
• Compaction
• Cementation (Calcite, Silica & Iron Oxide)
14. CLASSIFYING
• Detrital
• Materials that originate and are transported are derived
from mechanical weathering.
• Chemical
• Soluble materials that largely come from chemical
weathering that are precipitated either from organic or
inorganic processes.
15. DETRITAL CLASTIC
Size Range Particle Name Texture Common Detrital Rock
(mm) Name
> 256 Boulder
Conglomerate
64 - 256 Cobble Coarse (rounded edge)
Gravel
4 - 64 Pebble Grained Breccia
(angular edge)
2-4 Granule
1/16 - 2 Sand Medium Sand Sandstone
1/256 – 1/16 Silt Mudstone/
Very Fine
< 1/256 Clay Mud Siltstone/
Grained
Shale
16. BIOCHEMICAL NON-CLASTIC
Composition Texture Rock Name
Fine to coarse-grained Limestone
Coarse-grained fossils & fossil fragments loosely Coquina
Calcite
cemented
Fine-grained shells of microorganisms, clay Chalk
Dolomite Textures very similar to limestone Dolostone
Quartz Very fine-grained Chert/Flint
Gypsum Fine to coarse-grained Gypsum
Halite Fine to coarse-grained Rock Salt
Clastic – broken or fragmented
Non-clastic – not formed by mechanical breakup
17. FEATURES
• Strata or Beds
• Layers of sediments that were deposited
• Ripple Marks
• Nearly parallel ridges and troughs produced by moving
waters
• Mud Cracks
• Polygonal cracks that form when mud dries and shrinks
• Fossils
• Traces or remains of prehistoric life
18. METAMORPHIC
• Meta
• Change
• Morphosis
• Form
• Metamorphosis
• the process that changes the size, shape, texture, or even
mineral composition of pre-existing rocks due to heating
and pressure.
19. 3 AGENTS OF METAMORPHISM
1. Heat
• Provides energy to drive chemical reactions to
recrystallize minerals
2. Pressure
• Rocks located at a greater depth are quite warm and
behave plastically during reformation
3. Chemically active fluids
• Water that surrounds the crystals serves as the catylist
aiding the migration of ions.
20. 2 TYPES OF METAMORPHISM
• Regional
• Happens in rock when subjected to intense stress and high
temperatures associated with large scale deformation
• Ex. Mountain Building
• Contact
• Happens when rock is in contact with or near a mass of
magma.
• Ex. Volcanic Erruptions
21. CLASSIFYING
• Foliated
• Mineral alignment that gives rock a banded or layered
appearance
• Non-foliated
• Minerals that form equidimentional crystals is not visibly
foliated.
22. CLASSIFYING
Low Medium High Very High
Foliated M
Shale Slate Schist Gneiss E
Non-foliated L
T
Peat Lignite* Bituminous* Anthracite
I
Limestone Marble N
Quartz Quartzite G
* Still considered as sedimentary rocks.
