Earth Materials and Processes Understand Basic Concepts of:

Earth Materials and Processes
Understand Basic Concepts of:
• tectonic cycle
• hydrologic cycle
• geochemical cycle
• rock cycle (interaction with above three)
• minerals (silicates, oxides, carbonates, etc.)
• weathering -- chemical, physical
• erosion, transport, deposition, lithification
GEOL g406 Environmental Geology S. Hughes 2003

Tectonic Plates, Earthquakes, and Active Volcanoes
GEOL g406 Environmental Geology S. Hughes 2003

GEOL g406 Environmental Geology S. Hughes 2003

Earth Materials and Processes
The Rock Cycle
Tectonism
controls the rock
cycle and is
important to many
surficial
processes and
other Earth
Cycles.
GEOL g406 Environmental Geology S. Hughes 2003

Earth Materials and Processes
The Hydrologic Cycle
GEOL g406 Environmental Geology S. Hughes 2003

Earth Materials and Processes
The hydrologic cycle describes the movement
of water between the mediums of atmosphere, earth,
and ocean and back again. In the process, water
erodes the land, transports elements as sediment or in
solution, and provides essential water resources for
humans. Only 0.3 % of the total water in the cycle
available for human use.
QUESTIONS:
• Fresh water makes up what proportion of total
water on earth?
• Approximately what percent of water worldwide is
considered polluted?
GEOL g406 Environmental Geology S. Hughes 2003

Earth Materials and Processes
The Biogeochemical Cycle traces the movement of
an element, like carbon, in the air, water, on and in the land,
and as used by living organisms. This issue is of particular
importance today because large amounts of carbon dioxide
are produced by burning fossil fuels. Many scientists are
concerned that this trapped carbon dioxide may heat the earth
in a process known as the "greenhouse effect."
QUESTIONS:
• How much carbon dioxide enters the Earth’s atmosphere
each day?
• What is carbon dioxide’s residence time in the
atmosphere?
• Where does the carbon "go" when its residence time in the
atmosphere is over? (hint: check out the carbon cycle)
GEOL g406 Environmental Geology S. Hughes 2003

Strength of Rocks
GEOL g406 Environmental Geology S. Hughes 2003

Earth Materials and Processes
GEOL g406 Environmental Geology S. Hughes 2003

Strength of Rocks
Rock strength is highly variable.
Many Factors:
• rock type
•texture
• chemical composition
• internal structures
• presence or absence of fluids
Most rocks already fractured by joints and faults.
Fractured rocks are only as strong as whatever is holding the
rock together (gravity or friction).
• fracture along planes of weakness
• fracture along bedding planes or along foliation planes
• orientation of planes of weakness is important, Why?
GEOL g406 Environmental Geology S. Hughes 2003

Strength of Rocks
Some common rocks, shales for example, may share the
same name but have different engineering properties
depending on their deposition as well as lithification
processes.
Compaction shales are weak and can slide along
bedding planes, slake (soften into mud when wet), and swell
under certain conditions.
Cemented shales, depending on the cementing material,
can be very strong and suitable for most engineering
enterprises. Study the stress-strain diagrams carefully.
Read Table 2.1 in the textbook.
GEOL g406 Environmental Geology S. Hughes 2003

GEOL g406 Environmental Geology S. Hughes 2003

GEOL g406 Environmental Geology S. Hughes 2003

GEOL g406 Environmental Geology S. Hughes 2003

Earth Materials and Processes
Terms to Understand:
• hydrocompaction
• geologic cycle
• tectonic cycle
• rock cycle
• hydrologic cycle
• biogeochemical cycle
• greenhouse effect
• rock strength
• reliable strength
• safety factor
• stress and strain
• ductile and brittle substances
• elastic and plastic deformation
• proportional elastic limit
• ultimate strength
• rupture strength
Read Case Histories in the textbook:
Baldwin Hills Dam and St. Francis Dam
GEOL g406 Environmental Geology S. Hughes 2003