Lecture 15:
THE ROCK CYCLE
PHYSICAL GEOGRAPHY SPHERES
Atmosphere
Hydrosphere
Lithosphere
Magnetosphere
Cryosphere
Biosphere
Geog 1000 Introduction to Physical Geography Fall 2010 : Dr. Hester Jiskoot, University of Lethbridge
LECTURE STRUCTURE
1. What is a rock?
2. The rock cycle
3. Elements and minerals
4. Rock types & rock forming processes
5. What is YOUR rock?
See also Chapter 8 pp. 273-280
WHAT IS A ROCK?
THE ROCK CYCLE, main rock types and their rock forming processes
Sedimentary
Weathering
Transport
Deposition
Cementation
Compaction
A solid assemblage of minerals bound
together or a mass of a single mineral
Formed or reformed during one of 3
rock-forming processes
Igneous
Impermanent, but ‘longer-lived’ than you & me
Melting
Cooling
Crystallisation
Metamorphic
Heat
and/or
Pressure
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Element
Symbol
Minerals are inorganic element assemblages
% Weight
Example: two major mineral groups:
Oxygen
O
Silicon
Si
Aluminum
Al
8.1
Iron
Fe
5.0
Calcium
Ca
3.6
Sodium
Na
2.8
Potassium
K
2.6
olivine, pyroxene
Magnesium
Mg
2.1
• phyllosilicates = clay minerals
46.6
SiO2-Silica
All others
27.7
A) SILICATE MINERALS (Si)
• alumino-silicate (felsic) minerals Æ light
quartz, feldspar
• ferromagnesian-silicate (mafic) minerals Æ dark
1.5
Continental igneous: SiAl
Oceanic igneous:
SiMg
B) CARBONATE MINERALS (CO3)
calcite (calcium carbonate = CaCO3)
Æ SIAL Æ felsic
Æ SIMAÆ mafic
ROCK TYPE
SUBTYPE
EXAMPLES
Igneous
Intrusive
granite
Extrusive
rhyolite
Igneous or volcanic processes
*** Magma cools down ***
gabbro
Slow
How fast?
basalt
Metamorphic
Foliated
gneiss
schist
Non-foliated quartzite
Clastic
Fast
Crystals have NO time to form
Intrusive
Plutonic rocks
Extrusive
Lava
Where?
marble
Sedimentary
Crystals have time to form
sandstone
shale
Chemical
limestone
Biogenic
coal
Rock forming process = crystallisation
Volcanic rock types
GRANITE
Extrusive
Intrusive
BASALT
Fig 8.7, p. 277 of your book
2
Sedimentary processes
Small rock particles are eroded/dissolved,
transported & deposited as sediments
Clastic sediments
= mineral particles
Non-clastic sediments = chemical/organic precipitates or evaporites
FROM SAND = SEDIMENT
Rock forming process = Lithification
Lithification = Diagenesis = Cementation, Compaction & Hardening
TO SANDSTONE = ROCK
SHALE (ROCK)
WAS CLAY (SEDIMENT)
Sedimentary rocks
preserve the original
sedimentary layering of
particles and
stratification of beds
Metamorphic processes
*** Rocks deform under heat/pressure ***
LIMESTONE
Lithified Ca+-rich skeletons of sea animals
Easily soluble in water
Igneous rocks
Sedimentary rocks
Change physically or chemically under heat/pressure
Metamorphic rocks
Makes hard compact rocks
COAL
Peat Æ Lignite Æ Bituminous Æ Anthracite
Increasing degree of lithification and metamorphosis
Foliated
Non-foliated
Rock forming
processprocess
= metamorphism
Rock forming
= Metamorphosis
3
ROCK TYPE
SUBTYPE
EXAMPLES
Igneous
Intrusive
granite
Extrusive
rhyolite
gabbro
basalt
Metamorphic
GNEISS
Foliated
gneiss
schist
Non-foliated quartzite
marble
Sedimentary
Clastic
sandstone
Chemical
limestone
Biogenic
coal
shale
MARBLE
How to make a GNEISS…
http://seis.natsci.csulb.edu/bperry/metarock/METAMORPHISM.htm
DISTRIBUTION OF
“URBAN” GEOLOGY
Sandstone
Marble
Granite
Gneiss
What is YOUR rock?
MEANINGFUL GRANULAR
POWERFUL LIGHT DARK
?
DULL
LAYERED ?
SHINY
HEAVY LIGHT
SOFT
BEAUTIFUL
COLOURFUL
HARD WARM
ROUGH
?
SMOOTH
?
USEFUL
COLD
Which type is your rock?
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