Transcript Chapt12RHS2014x

Geology and Nonrenewable
Minerals
Chapter 12
Case Study: Real Cost of Gold
• Gold for 1 wedding band produces waste = to
weight of 3 cars• Waste typically left at mine
• Toxins used to extract (cyanide salts &
mercury)
Section 12-1
WHAT ARE THE EARTH’S
MAJOR GEOLOGICAL
PROCESSES AND HAZARDS?
The earth is a dynamic planet
• Geology -study of dynamic processes occurring on
the earth’s surface and in its interior.
Three major concentric zones.
1. core =innermost zone—extremely hot, with a solid inner
part encircled by a liquid core of molten /semisolid
material.
2. mantle—solid rock, but under its rigid outermost part is
the asthenosphere, a zone of hot, partly melted rock that
flows.
3. Crust – outermost / thinnest Continental vs Oceanic crust
The combination of the crust and the rigid outermost part of the mantle (above
the asthenosphere) is called the lithosphere.
Volcanoes
Abyssal hills
Oceanic
crust
(lithosphere)
Abyssal Oceanic
floor
ridge
Abyssal
floor Trench
Folded
mountain
belt
Craton
Abyssal
plain
Continental
shelf
Continental
slope
Continental
rise
• Convection cells cause rock to move
• Causes lithosphere to break up into a dozen tectonic plates.
•Continents have split apart and joined as tectonic plates drifted
Fig. 12-2, p. 277
atop the earth’s asthenosphere.
Plate Boundaries
– When two oceanic plates collide, a trench ordinarily
forms at the boundary between the two plates.
– When an oceanic plate collides with a continental
plate, the continental plate usually rides up over the
denser oceanic plate and pushes it down into the
mantle in a process called subduction.
– The area where this collision and subduction takes
place is called a subduction zone.
– Tectonic plates can also slide and grind past one
another along a fracture (fault) in the lithosphere—a
type of boundary called a transform fault.
Spreading
center
Subduction
zone
Oceanic
crust
Ocean
trench
Oceanic
crust
Continental
crust
Continental
crust
Cold dense
Material cools
material falls
as it reaches
back through
the outer
mantle
mantle
Mantle
convection
cell
Two plates move
towards each other.
One is subducted back
into the mantle on a
falling convection
current.
Hot
material
rising
through
the
mantle
Mantle
Hot outer
core
Inner
core
Fig. 12-3, p. 277
The earth’s major tectonic
plates
The San Andreas Fault
Internal pressure in a volcano can cause
lava, ash, and gases to be ejected
An earthquake has certain
major features and effects
Richter Scale
– Magnitude is measured by seismograph
– Richter scale -each unit has amplitude 10 times
greater than the next smaller unit.
– Insignificant (less than 4.0 on the Richter
scale).
The largest recorded
– Minor (4.0–4.9).
earthquake occurred
– Damaging (5.0–5.9).
in Chile on May 22,
1960 and measured
– Destructive (6.0–6.9).
9.5 on the Richter
– Major (7.0–7.9).
scale.
– Great (over 8.0).
How a tsunami forms
Earthquakes on the ocean floor can
cause huge waves called tsunamis
• They can travel across the ocean at the speed of a
jet plane.
• In deep water the waves are very far apart—
sometimes hundreds of kilometers—and their crests
are not very high.
• As a tsunami approaches a coast, it slows, its wave
crests squeeze together, and heights grow rapidly.
• Hits a coast as a series of towering walls of water
• Between 1900 and 2010, tsunamis killed an estimated
280,000 people along the Pacific Ocean.
Tsunamis 101
(National Geographic Video)
http://video.nationalgeograp
hic.com/video/environment/e
nvironment-naturaldisasters/tsunamis/tsunami101/
Section 12-2
HOW ARE THE EARTH’S
ROCKS RECYCLED?
Minerals
• A mineral is an element or inorganic compound that
occurs naturally in the earth’s crust as a solid with a
regular internal crystalline structure.
• Can consist of a single element such as gold, silver,
and diamond (carbon).
• Most of the more than 2,000 identified minerals
occur as inorganic compounds formed by various
combinations of elements, such as salt (sodium
chloride or NaCl) and quartzite (silicon dioxide or
SiO2).
There are three major types of
rocks
• Rock is a solid combination of one or
more minerals found in the earth’s crust.
– Some kinds of rock, such as limestone and
quartzite, contain only one mineral while most
consist of two or more minerals, such as
granite—a mixture of mica, feldspar, and
quartz crystals.
– Three broad classes:
• Sedimentary rock (e.g. sandstone, limestone).
• Igneous rock (e.g. granite).
• Metamorphic rock (e.g. slate, marble).
Simplified rock cycle
Takes place over millions of years
Section 12-3
WHAT ARE MINERAL
RESOURCES AND WHAT ARE
THE ENVIRONMENTAL
EFFECTS OF USING THEM?
We use a variety of nonrenewable
mineral resources
• A mineral resource is a concentration of
naturally occurring material from the earth’s
crust that can be extracted and processed into
useful products and raw materials at an
affordable cost.
– Found and extracted more than 100 minerals from the
earth’s crust.
– Examples are fossil fuels (such as coal), metallic
minerals (such as aluminum and gold), and
nonmetallic minerals (such as sand and limestone).
– Minerals are classified as nonrenewable resources.
We use a variety of nonrenewable
mineral resources
• An ore is rock that contains a large enough
concentration of a particular mineral—often a
metal—to make it profitable for mining and
processing.
– High-grade ore vs. Low-grade ore
Examples: Aluminum, steel, copper, gold
Each metal resource that we
use has a life cycle
There are several ways to
remove mineral deposits
I. Shallow mineral deposits are removed by
surface mining by:
– Removing vegetation.
– Removing the overburden or soil and rock
overlying a useful mineral deposit.
– Placing waste material set aside in piles, called
spoils.
1. Open-pit mining
There are several ways to
remove mineral deposits
2. Strip mining is useful and economical for
extracting mineral deposits that lie in large
horizontal beds close to the earth’s surface.
A. Area strip mining is used where the terrain
is fairly flat; a gigantic earthmover strips away
the overburden, and a power shovel removes
the mineral deposit.
B. Contour strip mining is used mostly to mine
coal on hilly or mountainous terrain.
There are several ways to
remove mineral deposits
3. Mountaintop removal uses explosives,
large power shovels, and huge machines
called draglines to remove the top of a
mountain and expose seams of coal.
Colbert Report Mountain Top Mininghttp://www.colbertnation.com/the-colbert-report-videos/261997/january18-2010/coal-comfort---margaret-palmer
II. Subsurface mining removes minerals from
underground through tunnels and shafts.
Harmful effects of extraction, processing, and use
of nonrenewable mineral or energy resources
Acid mine
drainage =
sulfuric acid
Mining produces 75% of all
solid waste in US & is a major
cause of air and water
pollution.
Types of mining
Open pit, strip, contour strip, and mountaintop removal
Open pit
Contour
strip
Subsurface mining
disturbs 1/10th as
much land as
surface mining &
usually produces
less waste
Strip
Mt. Top
Removal
Removing metals from ores has
harmful environmental effects
• Ore mining typically has two components:
– Ore mineral, containing the desired metal.
– Waste material (tailings)
• Heating ores to release metals is called smelting.
– Without effective pollution control equipment, smelters
emit enormous quantities of air pollutants, including
sulfur dioxide and suspended particles.
Section 12-4
HOW LONG WILL SUPPLIES
OF NONRENEWABLE
MINERAL RESOURCES LAST?
Mineral resources are
distributed unevenly
• Abundant : iron and aluminum.
• Scarce: Manganese, chromium, cobalt, and
platinum.(Strategic metal resources)
• Uneven distribution of mineral resources.
• USA, Canada, Russia, South Africa, and Australia—
supply most of world’s mineral resources
• Economic Depletion- costs too much to exploit
remaining deposits
• What to do after economic depletion? Recycle/reuse,
waste less, find substitute, do without
Market prices affect supplies of
nonrenewable minerals
• Most well-developed countries use subsidies, taxes,
regulations, and import tariffs to control the supply,
demand, and price of minerals.
• Most mineral prices are kept artificially low.
• Extraction of lower grades of ore is possible due to
technological advances. Good idea?
• Biomining (in-place, or in situ) -use or microorganisms to
break down rock material and extract minerals.
• Importance of rare earth metals – see p. 291
Can we get more of our
minerals from the oceans?
• Some ocean mineral resources are dissolved in
seawater, but Low concentrations take more
energy and money than they are worth.
• Hydrothermal ore deposits are rich in minerals
such as copper, lead, zinc, silver, gold, and
some of the rare earth metals.
• Growing interest in deep-sea mining.
• Manganese nodules cover large areas of ocean
floor. (contain rare earth metals)
Section 12-5
HOW CAN WE USE MINERAL
RESOURCES MORE
SUSTAINABLY?
We can find substitutes for
some scarce mineral resources
• Human ingenuity will find substitutes.
• Current materials revolution in which
silicon and other new materials,
particularly ceramics and plastics, are
being used as replacements for metals.
• Finding substitutes for scarce minerals
through nanotechnology.
• We can recycle and reuse valuable metals
We can use nonrenewable mineral
resources more sustainably
Three big ideas
• Dynamic forces that move matter within the earth and on
its surface recycle the earth’s rocks, form deposits of
mineral resources, and cause volcanic eruptions,
earthquakes, and tsunamis.
• The available supply of a mineral resource depends on
how much of it is in the earth’s crust, how fast we use it,
the mining technology used to obtain it, its market prices,
and the harmful environmental effects of removing and
using it.
• We can use mineral resources more sustainably by
trying to find substitutes for scarce resources, reducing
resource waste, and reusing and recycling
nonrenewable minerals.