Download Chapter 8: Major Elements

Minerals vs. Rocks
Common silicate minerals:
Olivine- independent tetrahedra joined by Fe or Mg
Pyroxene- single chains of linked tetrahedra
Amphibole- double chains of linked tetrahedra
Micas and Clays- 2-D sheets of linked tetrahedra
Quartz- 3-D framework of fully polymerized
tetrahedra
Feldspar- also a 3-D framework, but Al, Na, Ca, or
K can substitute
Minerals vs. Rocks
Common non-silicate minerals:
Calcite- CaCO3 a carbonate
Dolomite- CaMg(CO3)2
Apatite- Calcium phosphate (PO4)
Halite- NaCl
Gypsum- hydrated CaSO4
Rock Types

Igneous
Ultramafic
Mafic
(hi Mg-Fe)
(hi Mg-Fe)
Intermediate
Silicic
(hi Si-Al)
Volcanic
Basalt
Andesite
Rhyolite
Plutonic Peridotite
Gabbro
Diorite
Granite
Rock Types

Igneous
Polished slab of granite
10 cm across
Thin section of basalt
4 mm across
Rock Types

Sedimentary
Clastic
Chemical

> 2 mm
0.6 - 2 mm
Cobbles, Pebbles
Sand
Conglomerate
Sandstone
0.6 < 0.004 mm
0.004 mm
Silt
Clay
Shale
CaCO3
CaMg(CO3)2
SiO2
NaCl, KCl, etc.
Limestone
Dolostone
Chert
Evaporites
Metamorphic
2) The Earth’s Interior
General
Geological
Principles:
1) Geologic
Time
Geologic Time

Relative dating by superposition, cross-cutting
relationships, fossils and evolution
Geologic Time


Relative dating by superposition, cross-cutting
relationships, fossils and evolution
Absolute dating by radioactive decay (igneous)
1
½
¼
time 
Isostasy
Wood density 0.5
8g
2g
3g
5g
5g
3g
2g
Water density 1.0
Each block weighs 2 g
0.5
0.3
0.2
density
= 0.1
0.2
Water density 1.0
0.3
0.5
Isostasy
Isostasy
3) Plate Tectonics
Divergent and Transform Plate Boundaries
Continental
Rifting
Continental
Rifting
the East
African
Rift
Convergent
Plate
Boundaries
“Andean-type”
orogenesis
Crust thickens by
addition of magma
 Compression due to
plate convergence

Convergent Plate Boundaries
The Origin of the Himalayas
“Himalayan-type”
orogenesis
Begins as Andean-type
“Himalayan-type”
orogenesis
How do you locate the “suture zone” today?
How can you determine the “polarity” of subduction?
Slivers of oceanic crust and upper mantle (ophiolites)
The “suture zone” is marked by the mélange and
become incorporated into the “mélange” in the
particularly by the occurrence of ultramafic rocks
accretionary wedge of deformed sediments
composing the mantle portion of the ocean lithosphere
Chain of ultramafic bodies in Vermont indicating a
suture zone of the Ordovician Taconic Orogeny. The
ultramafics mark a closed oceanic basin between
North American rocks and an accreted island arc
terrane. From Chidester, (1968) in Zen et al., Studies
in Appalachian Geology, Northern and Maritime.
Wiley Interscience.
Appalachian
History
Can “accrete”
island arc
terranes as well
as continents
Accreted
Terranes of
the Western
Cordillera
Hot Spots
The Plate Tectonic
Regime of the Western
USA
Earthquakes and Plate Tectonics
General
Geological
Principles:
4) The Rock
Cycle
Plate Tectonics and the Rock Cycle
Examples of Other
Cycles: the Hydrologic
Cycle
Examples of Other Cycles:
the Carbon Cycle
Population
Population
Population
Impacts:
Resources
Waste Disposal
Pollution
Hazards/Disasters
Farmland and Food/Soil
Disruption of Natural Systems
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