Transcript PPT on Minerals and Review Ch14

Geology and
Nonrenewable
Resources
Chapters 14
Living in the Environment, 16th Edition, Miller
Advanced Placement Environmental Science
Edited by Ms. Wilkins, Original slide show from
La Canada High School
Dr. E
A View of Earth

Earth’s four spheres
» Solid Earth
» Hydrosphere
» Atmosphere
» Biosphere
Distribution of Elements


More than 100 elements in
entire Earth, but 99% of
Earth's mass is made up of only
8 elements
Whole Earth:
Fe>O>Si>Mg>Ni>S>Ca>Al
(others constitute < 1%)

Earth's crust
O>Si>Al>Fe>Mg>Ca>K>Na
(other constitute <1%)
Composition of Earth’s Crust
Earth’s Crust
Oxygen 46.6%
All others 1.5%
Magnesium 2.1%
Silicon 27.7%
Potassium 2.6%
Sodium 2.8%
Calcium 3.6%
Iron 5.0%
Fig. 10.4, p. 213
Aluminum 8.1%
Earth Structure
Has huge economic and Political consequences
Important to understand the
distribution of elements and minerals
determined during earths formation.
Compositional layers
 Core
Minerals unevenly distributed because
of density
Also, isolated sites- ex diamonds must
be exposed to extreme heat and
pressure.
- Fe,Ni.
 Mantle - compositionally homogenous, made
up of peridotite rock
 Crust - compositionally heterogeneous, lots of
rock types
Rock Cycle
Recycles
scarce
minerals and
elements
http://www.cotf.edu/ete/modules/msese/earthsysflr/rock.html
Igneous

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Rock formed by cooling and
crystallization of magma
If the cooling occurs at the surface, it is called extrusive
igneous
If the cooling occurs in the Earth, it is called intrusive
igneous
Extrusive igneous usually cools fairly rapidly and
therefore has smaller crystals than intrusive
Examples: Granite, Basalt, Quartz, Mica, Feldspar,
Obsidian
http://hvo.wr.usgs.gov/hazards/dds24167_L.jpg
Sedimentary Rock



Rock formed by the piling of material
over time
Sediment is compressed, heated and
chemically changed over long period
of time
Examples: Sandstone, Shale, Gypsum,
Limestone, Chalk
http://realgar.mcli.dist.maricopa.edu/alan/pix/grand-canyon.jpg
Metamorphic Rock
 Igneous
or
sedimentary rock
subjected to
tremendous
pressure and heat
 Examples: Slate,
Marble, Quartzite
Lithosphere
Lithosphere
is divided into
plates (about 13 major plates
and several smaller ones).
Consists
of rigid, brittle crust
and uppermost mantle.
Plate tectonics explains wide range of geological
phenomenon (volcanism, earthquakes, orogenesis,
fossil distributions, etc.)
Evidence for Continental Drift
 Coastline fit
 Alignment of mountain ranges
 Similar Rock Sequences
 Fossils
 Modern Fauna
 Ancient climates
Evidence for Continental Drift
Idea was revived in 1950’s and developed
into Plate Tectonics
 Theory of plate tectonics accepted by nearly
all geologists.
 Plate tectonics explains wide range of
geological phenomenon (volcanism,
earthquakes, orogenesis, fossil distributions,
etc.)

Plate Tectonics
 Bathymetric
observations during
WWII and earthquake data set
stage for Plate Tectonics.
 These
observations are now
combined to form the theory of
plate tectonics.
Plate Boundaries
 Defined
 Depths
by earthquake data.
of earthquakes indicate
types of boundaries.
Plate Boundaries
Plate Boundaries
 Divergent
Boundaries
– Places where plates are coming apart
 Convergent
Boundaries
– Places where plates crash or crunch
together
 Transform
Boundaries
– Places where plates slide past each other
Convergent Boundaries
Crust destroyed at convergent margins,
mountain building
 Three types:

– Ocean-Ocean
– Ocean-Continent
– Continent-Continent
Ocean-Ocean Convergent
Boundaries

Deep oceanic trenches
Ocean-Ocean Convergent Boundaries
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
Earthquakes define zone dipping into mantle (Benioff zone)
Zones around Pacific dipped about 45o toward the
continents
Ocean-Continent Boundaries

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Heat added to crust by magmas causes regional
and contact metamorphism
Heat added also produced more felsic magma
types by crustal assimilation/fractional
crystallization
Stratovolcanoes built on continental crust =>
continental volcanic arc
Deep-sea trench and accretionary wedge
(melange) along coast of continent
Examples: Andes, Cascades, Central America
Ocean-Continent Boundaries
Magmas produced in mantle wedge above
subducting slab
 Much ascending magma stalls in continental crust > batholith (roots of volcanic arc)

Transform Boundaries
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Most fracture zones connect segments of mid-ocean ridges
Areas of different water depth on each side of fracture zone
Shallow earthquakes occur on transforms between sections
of mid-ocean ridge
Transform Boundaries
Connect other plate margins (convergent and
divergent)
 San Andreas Fault - on land transform (Pacific plate
sliding north relative to North America)

Hot Spots
Columns of hot material rising through
mantle (plumes).
 Hot spot fixed in position underneath
moving lithospheric plates

Driving Forces of Plate Tectonics
 Plate
movement due to Earth's
attempt to lose internal heat
 Conduction
 *Convection
Driving Forces of Plate Tectonics
Plate movement due to Earth's attempt to lose internal heat
Conduction & Convection
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Gravity-driven sliding
Plate slide down sides of
mid-ocean ridge
Gravity gives the push,
not magmas at ridge
Ridge push is probably
the main force on plates
Flow of material
associated with hot
spot plumes drives
plates
 Columns of rising
material vs.
convection cells
 Chaotic convection
in mantle (plumes
of rising material)

EARTHQUAKES
http://www.howstuffworks.com/earthquake6.htm
Earthquakes
Most destructive forces on Earth. But
it is buildings and other human
structures that cause injury and death,
not the earthquake itself
1988 - Soviet Armenia: magnitude 6.9, 25,000 people died
1985 - Mexico City: magnitude 8.1, 9500 people
1989 - Loma Prieta, CA: magnitude 7.1, 40 people died
1995 - Kobe, Japan: magnitude 7, ~6000 people died
30,000
earthquakes
occur worldwide
annually that are
strong enough to
be felt
Typically only 75
of them are
considered to be
significant
Vibration of earth produced by rapid release of
energy (seismic waves) with radiate in all
directions from the source (focus)
 Like ripples from dropping a stone in a pond,
energy dissipates with distance
 Earthquakes don't occur randomly. Occur on
faults or fractures within the earth

Explained by plate tectonics.
Most occur on plate boundaries
 Sometimes in plate interiors
if enough stress is built up

Types of Waves
Earthquake waves = seismic waves.
Recorded on seismometers on seismographs.
Types of Waves
 Surface waves - travel on Earth's surface, away
from epicenter.
– Very slow waves. Cause a lot of damage, rolling feeling
at end of earthquake

Body Waves - travel through Earth's interior,
spread outward from focus
Body Waves
P waves:
 Pressure or compressional waves. Vibrate parallel to
direction of wave travel like a slinky.
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
Fast travel: 4-7 km/sec (15,000 mph)
P is primary, or first wave to arrive at recording station
S waves:
 Shear waves. Vibrates perpendicular to direction of wave
travel. Like snapping a rope
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Slower than P wave: 2-5 km/sec (11,000 mph)
So S is secondary, or second wave to arrive at recording
station
VOLCANOES
http://georoc.mpch-mainz.gwdg.de/volcano.gif
Volcanoes
• Located at plate boundaries & EQ zones (why ?)
• Result in surface pyroclastic and extrusive rocks
• Pyroclastic : particles thrown into air during eruption
- settle to form ash, tuff & agglomerate
• Magma extruded to surface to form extrusive igneous
rocks (lava), e.g rhyolite, andesite & basalt (type
depends on acidity)
– Acidic : viscous, flows poorly
– Basic : more fluid - flows on very gentle slopes over vast
areas, e.g basalt plains of Victoria
Volcanoes

Basic parts of a volcano

Crater (depression at the summit of a volcano,
connected by a vent or pipe to the magma
chamber below)
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Caldera (crater more than 1 km in diameter,
formed at the summit of a volcano when lava is
drained from an underground magma chamber,
causing the summit of the volcano to be
unsupported, and to collapse)
Sedimentary rock
Sediments glued
together
Igneous rock
Heat
Metamorphic rock
Heat and pressure
http://volcano.und.nodak.edu/vwdocs/vw_hyperexchange/parts.html
Shield Volcano
Mauna Loa, on the Big Island of Hawaii, is the largest active
volcano in the world. It last erupted in 1984. Mauna Loa erupted 14
times in the 20th Century, and 37 times since 1832. Mauna Loa is
the most massive mountain on Earth, rising to an elevation of 13,677
feet above sea level, or 31,677 feet above the sea floor. Its volume is
10,000 miles3.
2. Cinder cones
 Erupt pyroclastic material
 Steep slopes (30 to 40 degrees)
 Not very long lived.
 Typically small, less than 1000 feet tall
 Often parasitic on larger volcanoes
Examples: Paricutin in Mexico, Sunset crater in
Arizona
Cinder cones
Composite
Volcano
Sedimentary rock
Chemical and
physical weathering
Igneous rock
Heat –magma (lava)
Metamorphic rock
Heat and pressure
Yellowstone Caldera
Eruptions from Volcanoes
May produce ejecta, (lava rock or ash), molten
lava, and/or toxic gases.
 Gases: H2O, CO2, SO2, HCl
 Occur when pressure within magma chamber
forces molten magma up through a conduit and out
a vent.
 Benefits: new landforms, minerals, and nutrients
from broken down lava

Eruption of Mount Saint
Helens, May 18, 1980
The eruption of Mount Saint Helens was the most
destructive in the history of the United States
 Mount Saint Helens is located in southwest
Washington in the Cascade Range, a mountain
range dominated by periodically active volcanic
peaksIn
 Images include pre-eruption activity and posteruption effects such as the blast area, mud flows,
ash fall, and altered terrain
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http://www.ngdc.noaa.gov/seg/hazard/slideset/31/31_thumbs.html
Minerals and Rocks
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What is a mineral?
– naturally occurring, inorganic, solid element or compound
with a definite chemical composition and a regular internal
crystal structure
What is rock?
– solid, cohesive, aggregate of one or more minerals
– Each rock type has a characteristic mixture of minerals
What is an Ore?
– Rock with large concentration of a particular maineral to
make it profitable
– High and low grade ores
» NON- Metalic Mineral

Sand, gravel, limestone
» Metalic

Aluminum, Steel, manganese, cobalt, chromium, Copper, Gold
Mining: Extract Ore from Ground
Types of Mining:
• Surface Mining: Scoop ore off surface or earth.
• cheap.
• safe for miners.
• large environmental destruction.
• Underground Mining: Use of shafts to reach deeply buried ores.
• expensive.
• hazardous for miners.
• less environmental damage.
Average Concentration of
Valuable Metals in the Crust
Aluminum ~8%
Iron
~5% most Fe and Al is in silicate minerals
and is not used as an ore
Titanium 0.44%
Nickel
75 ppm or 0.0075%
Zinc
70 ppm or 0.0070%
ppm =
Copper 55 ppm 0.0055%
parts per million
Lead
13 ppm or 0.0013%
Silver
0.07 ppm
Gold
0.004 ppm
Strip Mining
strip-mining: scoop off rock
overburden, and then scoop off
ore material.
• Economics of strip mining
depend on stripping ratio
• Large land area can be involved,
especially for coal and bauxite.
Surface Mining
open pit mining:
• circular hole in ground, with ramp
circling down along sides, allows
deeper ore to be reached.
Gold in Quartz

A large quartz boulder with a lot of visible gold.
Usually, the gold is much finer and hard to see.
Placer Deposition
Panning for
gold in a
placer
deposit
Aeolian Placers
The "diamond crawl" in a
deflation basin, Diamond
Area No 1, Namibia
 Diamond concentrations
were increased by wind
erosion

Cassiterite

tin oxide ore mineral, SnO2. It is generally
opaque but is translucent in thin crystals. Its
luster and multiple crystal faces produce a
desirable gem. Cassiterite has been the chief
tin ore throughout ancient history and
remains the most important source of tin
today
US General Mining Law of
1872
Acid Mine Drainage
Nonrenewable
Mineral
Resource
Depletion
Curves
Source: Miller, G. Tyler, Living In The
Environment. (2000) Wadsworth
Publishing. New York.