Lecture 14:
THE ROCK CYCLE
PHYSICAL GEOGRAPHY SPHERES
Atmosphere
Lithosphere
Magnetosphere
Hydrosphere
Cryosphere
Biosphere
Geog 1000 Introduction to Physical Geography Fall 2012 : 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 1 of 3
rock-forming processes
Igneous
Impermanent, but ‘longer-lived’ than you & me
Melting
Cooling
Crystallisation
Metamorphic
Heat
and/or
Pressure
1
ROCK COMPOSITION
Element
Symbol
Minerals are inorganic element assemblages
% Weight
Example of two major mineral groups:
Oxygen
O
46.6
Silicon
Si
27.7
Aluminum
Al
8.1
Iron
Fe
5.0
Calcium
Ca
3.6
Sodium
Na
2.8
Potassium
K
2.6
Magnesium
Mg
2.1
SiO2-Silica = Most sand
Used for glass
a) SILICATE MINERALS (Si)
• alumino-silicate (felsic) minerals Æ light
quartz, feldspar
• ferromagnesian-silicate (mafic) minerals Æ dark
olivine, pyroxene
• phyllosilicates = layered
clay minerals
1.5
All others
Continental igneous: SiAl
Oceanic igneous:
SiMg
b) CARBONATE MINERALS (CO3)
Æ SIAL Æ felsic
Æ SIMAÆ mafic
ROCK TYPE
SUBTYPE
EXAMPLES
Igneous
Intrusive
granite
Extrusive
rhyolite
calcite (calcium carbonate = CaCO3)
Igneous or volcanic processes
*** Magma cools down ***
Rock forming process = crystallisation
gabbro
through cooling
basalt
Metamorphic
Foliated
Slow
gneiss
How fast?
schist
Non-foliated quartzite
marble
Sedimentary
Clastic
sandstone
limestone
Biogenic
coal
Fast
Crystals have NO time to form
Intrusive
Plutonic rocks
Extrusive
Lava
Where?
shale
Chemical
Crystals have time to form
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)
Used to be 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
Rock forming process = metamorphism
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
Foliated
Non-foliated
Increasing degree of lithification and metamorphosis
3
METAMORPHIC GRADES
dependent on TEMPERATURE and PRESSURE
GNEISS
LOW GRADE ------------- INTERMEDIATE --------------- HIGH GRADE
Greenschist ------------- Amphibolite ----------------------- Granulite
MARBLE
Slate --- Phyllite ---------- Schist ---------------------- Gneiss --- Migmatite
ROCK TYPE
SUBTYPE
EXAMPLES
Igneous
Intrusive
granite
Extrusive
rhyolite
How to make a GNEISS…
http://seis.natsci.csulb.edu/bperry/metarock/METAMORPHISM.htm
DISTRIBUTION OF
gabbro
basalt
Metamorphic
Foliated
gneiss
schist
Non-foliated quartzite
marble
Sedimentary
Clastic
sandstone
shale
Chemical
limestone
Biogenic
coal
“URBAN” GEOLOGY
What is YOUR rock?
Sandstone
MEANINGFUL GRANULAR
Marble
Granite
POWERFUL LIGHT DARK
?
DULL
LAYERED ?
SHINY
HEAVY LIGHT
SOFT
BEAUTIFUL
COLOURFUL
HARD WARM
ROUGH
?
SMOOTH
?
USEFUL
COLD
Which type is your rock?
Gneiss
Pyrenees, Spain
Granum cemetery, Alberta
4
Reading for Wednesday
Chapter 9 p. 310-323
Orogenesis and Earthquakes
5