I. Lecture Content
What
is Geology?
Observing Nature:
Consciousness and the Act of Perception
Earth from a Scientific
Perspective - A Systems Approach
Geology and
Human Civilization
Geologic Studies, the
Scientific Method & Theory
Origin of
Earth and our Solar System
Why is
Earth a Dynamic Planet?
Overview of Plate Tectonic
Theory
The
Hydrologic and Rock Cycles
Geologic
Time and the Principle of Uniformatarianism
II.
What is Geology?
A. Word comes from Greek: geo = earth; logos = study
B. The Scientific Study of Planet Earth
1. A very broad field of study:
Ø
The
earth's internal structure and composition, its dynamic character (earthquakes,
volcanoes, plate tectonics), and the processes that occur within it
Ø
The processes that shape the surface of the
Earth, and the materials that constitute its surface layers
Ø
The origin, occurrence, extraction and conservation
of the Earth's natural resources - minerals, fossil fuels, soils, water
Ø
Earth's place within the Solar System
Ø The history of life on Earth
2. Geologic study is divided into
two major areas:
· Physical = materials and
processes
· Historical = origin and
evolution
C. The Discipline of Geology is Very
Broad and Diverse
1.
Geochronology
2.
Planetary Geology
3.
Paleontology
4.
Economic Geology
5.
Environmental Geology
6.
Geochemistry
7.
Hydrogeology
8.
Mineralogy
9.
Petrology
10. Geophysics
11. Structural Geology
12. Seismology
13. Geomorphology
14. Oceanography (marine geology)
15. Paleogeography
16. Stratigraphy/ Sedimentology
17. Tectonics
18.
Volcanology
19. Engineering Geology
D. Geological Science Research -
"Pure" Versus "Practical"
1. "Pure" = sake of
curiosity and scientific knowledge
Examples: Studies of Trilobites; Age of the Earth
2. "Practical" = solving
human-related problems or concern
Examples: Oil Exploration;
Geologic Hazards; Mining
E. Economical & Environmental Aspects of Geology
1.
Economical = Geology impacts local & global economies
Examples: Mineral &
Energy Resources; Engineering
2. Environmental
= Geology affects local & global ecosystems
Examples: Geologic Hazards;
Pollution; Development
F. Interesting & Rewarding Careers in Geology
III. Observing Nature Through the Human
Experience
A.
Making Sense of Mother Nature and the Universe
1. Humans have an amazing capacity
for exploring and
understanding nature and the Universe.
2. Humans take great efforts in searching for and defining
the order and relationships between matter, energy, and
life amidst a mind-boggling backdrop of cosmic chaos.
B. The
Tricky Thing We Call (Human) Perception
1. Identification, evaluation and
categorization of objects
2.
Complex process of comparing different objects & events
3.
Prioritizing sensory (experiential) input (objects & events)
4.
Constantly creating a "perceived" reality (occurring now) based
on a "remembered" reality (the
past)
5.
Personal and societal perceptions of Life on Earth are
based on popularly-held belief systems
C.
The Means of Understanding the Nature of Things
1. Human Senses - Input of Information
2. Human Mind - Information
processing (Thinking)
Ø "Mapping" how
everything is connected together
Ø Finding out How and why
things change the way they do
Ø Making explanations and predictions
of phenomena's behavior
3. Technology - Extension of input
and processing abilities
Ø
Input
- Sensitive, sophisticated instruments
Ø Process - Computers
IV. Systems Approach To Understanding the
Earth
A. The Science Perspective of Earth
1. Rational, analytical approach
to studying the Earth
2. Based upon empirical,
reproducible evidence (facts)
3. Testable interpretations
(hypotheses & theories)
4. Always open to debate and
modification
B. The System-Subsystem Conceptualization
of Earth
1. The Concept of a System -
Combination of related parts
(subsystems) that interact in an organized fashion.
2. Individual Systems are
characterized by the dynamic
transfer of energy, matter, and
information:
· Input = into the system from
outside (the system)
· Output = out of the system
to outside (the system)
· Process = transfer
within/between subsystems
3. Very useful for
understanding complex things such as
Earth or a human body
4. The Earth can be described as
being a limited System
having a virtually
limitless set of Sub-systems
C. The Principle Subsystems of Earth
1. Core
2. Mantle
3. Lithosphere
4. Biosphere
5. Hydrosphere
6. Atmosphere
D. Complex Interactions Among Earth's
Subsystems
1. The Rock Cycle
2. The Hydrologic Cycle
3. The Biological Cycle
4. Plate Tectonics - the
"Supercontinent Cycle"
V.
Geology and Human Civilization
A. The Human
Experience Has Been Shaped by Geology
1. Every
human society, past & present, developed their
unique character and perceptions through daily interaction
with
their surrounding dynamic environment (land, sea, air &
life)
· Weather and Climate
· Natural Disasters
· Habitation & Resources
· Cultural Behaviors &
Belief Systems
· Religions & Spirituality
2. Humans are quickly becoming a
major geologic force
B. Geology Affects Every Person's Everyday Life
1. Same factors as defined above
C. Important Global, Regional and Local
Geologic Issues
1. Volcanic eruptions
2. Earthquakes
3. Tsunamis
4. Flooding
5. Mining and Oil Drilling
6. Dams Building
7. Environmental Degradation
8. Urban Development
9. Water Conservation
10. Climate Change
VI. Geologic Studies, the Scientific
Method & Theory
A. Geologic Research is Conducted in a Scientific Manner
1. Clear stated purpose
2. Well thought out &
carefully planned
3. Follows a set of logical and rational guidelines
outlined
in a
step-by-step method called the Scientific Method
4. Collaboration, review,
and debate with fellow geologists
5. Always open to scrutiny,
challenge, and modification
from
the scientific community and the world at large
B. The Scientific Method - A Set-by-Step Research
Plan
1.
Observation - Observe something in nature,
using your
bodily senses or
sensing instruments.
2. Question - Ask a question about what
you observe.
3. Hypothesis - Predict what you think the
answer to your question
might be. (Hypothesis = an interpretation or model)
4. Method - Figure out a way to test
whether or not your hypothesis
is correct. Note that the
outcome must be measurable,
i.e. quantifiable and reproducible.
5.
Result -
Perform the experiment using the method you came up with,
and record
the results. Repeat the experiment to
confirm you
results.
6.
Conclusion - You state whether your prediction was confirmed or not
and
try to explain your results.
7. Follow up - Repeat above steps
(modify research plan) until your
hypothesis confirms your results.
C. The Development of Hypotheses and
Theories
1. A hypothesis becomes an
acceptable model after repeated tests that
repeatedly confirm the
hypothesis's prediction.
2. A hypothesis becomes elevated
to a theory only after years of rigorous,
exhaustive tests and
scrutiny by the world scientific community.
VII.
Origin of Our Earth and Solar System
A. Solar System Formed from
Interstellar Gas & Dust
1. Material came from two sources
· Original primordial gases
left over from Big Bang
ü Mostly Hydrogen & Helium
· Secondary material from
exploded star(s)
ü All sorts of elements from H
to Uranium
ü Both gases and solid matter
2. Coalescing of cold matter caused by gravitational
fields
· Gravity waves through
interstellar space
· Increasing gravity force of
condensing matter
B. Earth Accreted from the Rotating Solar
Nebula Disc
1. Condensing Solar nebula cloud
began rotating
2. Increasing angular momentum
caused nebula to flatten
from an irregular mass into a spinning disc-like form
3. Central mass condensed into the
"proto" Sun
4. Outer mass coalesced into many
planetisimals, which
eventually lumped together
to form "proto" planets
5. Over time, the
"proto" planets swept up the remaining
planetisimals to become
the nine known planets
6. Inner planets, including Earth,
formed mainly from the
cold accretion of solid materials (heavier
elements)
· Metals (mostly iron,
magnesium & nickel)
· Silicates (rich in oxygen,
silicone, and aluminum)
7. Outer planets, like Jupiter,
formed mainly from volatiles
and gases (lighter
elements)
· Hydrogen & Helium
· Water & Carbon Dioxide
· Ammonia & Methane
8. Accretion process probably took
1 BY to 500 MY
C. Age of Earth & Solar System is
about 4.6 Billion Years
Ø Age come from the dating of
meteorite & Moon samples
D. Infant Earth Underwent Further
Differentiation
1. Extreme heating of Early Earth,
due to released energy from
gravitational collapse,
causes Earth to become molten
3. Segregation of Core and
Mantle (facilitated by molten condition)
4. Theorized collision of a
Mars-sized planet with Earth to
form the Earth-Moon system - Extremely violent event
5. Intense period of planetisimal
bombardment (~ 3.5 BYA)
6. Sufficient cooling to
create a solid, thin, & very mobile
lithosphere made up of many fast-moving micro plates
7. Earth's atmosphere underwent
drastic changes (~ 2.5 BYA)
VIII.
Why is Earth Dynamic and Constantly Changing?
A. Evidence of Continual Change Since Accretion
1. Profound differences in character of the Earth's rock
record for different periods of geologic time
Ø Unique rock types; their abundance & occurrence
Examples:
Komatiites
Sedimentary iron beds
Anorthosites
Greenbelts
Glacial tillites
Ø Unique fossils; their abundance & occurrence
Examples: Trilobites
Ammonites
Dinosaurs
Ø Distinctive tectonic terranes and their locations
Examples:
Wrangalia
Ophiolites
Southern California & Baja
Mount Everest & the Himalayas
2. Present-day geologic activities and events
Ø Earthquakes; Volcanic
eruptions; Uplift & Erosion
B.
Powerful Driving Forces Sustain Earth's Dynamism
1. Internal Forces
ü
Gravity
- Increases with accretion of matter
ü
Radioactive
decay - Release massive amounts of heat
ü
Rotational
momentum - Coriolis effect; other effects
ü
Organic
Life - Biochemical terra-forming
2. External Forces
ü Solar Wind - Sunshine, EMR
and nuclear particles
ü Heavenly body gravitational
fields
ü Bolides (comet and meteor
impacts)
C.
Driving Forces Produce Heat and Density Gradients
1. Gravity and radioactive
decay generate internal Earth heat
ü Gravitational heat left over
form accretionary event
ü Sustained nuclear
"barbeque" in mantle and crust
2. Internal Gravity and Thermal energy generate density
contrasts in the solid
Earth = Internal layering
ü Core
ü Mantle
ü Crust
3. Solar radiation generates thermal and
density contrasts in
the hydrosphere and
atmosphere
ü Dynamic Layering and
Circulation Patterns
4.
Gravity of the Moon and Sun generate tidal forces on Earth
ü Ocean tides
IX. The Plate Tectonic Theory – A simple
Overview
A. Earth's Outermost Solid Layer is
called Lithosphere
1. Consists of two parts
(sub-layers)
· Crust (top part)
· Uppermost mantle (bottom
part)
2. Two major types of Lithosphere
· Continental lithosphere
· Oceanic lithosphere
3. The lithosphere "floats" on top of the partially melted
Athenosphere
4. The lithosphere is made-up of a
number of separate,
irregular segments called tectonic plates
· Six major plates
· Six or so minor plates
B. The Lithospheric Plates are Mobile
1. The plates move over the
underlying mantle
2. Each plate has a separate and
unique plate motion
3. The tectonic plates jostle with
one another
4. Plates interact with one
another in three different ways
C. There are Three Types of Plate
Boundaries
1. Divergent
- plates move away from each other
2. Convergent
- plates toward each other
3. Transform
- plates slide past each other
D. Plate Boundaries are the Primary Site of
Present-day
Mountain Building Events (Orogenies)
1. Major Earthquakes
2. Volcanism
3. Crustal Uplift
4. Folding & Faulting
E. Seafloor Spreading Occurs at Divergent Boundaries
1. New oceanic lithosphere is
created where two plates are
actively pulling away from one another
2. Predominant regional tensional
forces at work
3. Site of the spectacular
mid-ocean ridge system
4. Examples: Mid Atlantic Ridge
& East Pacific Rise
F. Subduction Occurs at Convergent
Boundaries
1. Old, dense oceanic lithosphere
plunges back into the
underlying mantle
2. Predominant regional
compressional forces at work
3. The site of a paired oceanic trench/
volcanic arc system
4. Examples: Cascades, the Andes,
the Alps, & Himalayas
G. The Plate Tectonic
Theory is a Unifying Principle
1. Best explains the
relationships between many different
and seemingly unrelated geologic phenomena
2. Provides a sort of
predictive "map" for explaining, past, present
and future geologic phenomena & events
X. The Rock and Hydrologic Cycles
A. The Rock Cycle
1. A multi-process recycling
(creation & destruction) of
one rock type into another
2. Three major rock types
(material reservoirs)
· Igneous
· Sedimentary
· Metamorphic
3. Several
major multi-step rock-forming processes
· Partial melting (magma),
cooling & crystallization
· Weathering, erosion,
deposition, compaction, &
cementation
and/or crystallization
· Recrystallization &
neocystallization of solid rock
under
elevated temperature and/or pressure
4. The various rock reservoirs and
related processes are
all interconnected under the
title: Rock Cycle
B. The Hydrologic Cycle
1. A multi-process
(re)cycling of water between the
hydrosphere, atmosphere, and lithosphere
2. Several major water reservoirs
· Ocean
· Atmosphere
· Glaciers
· Lakes and Rivers
· Groundwater
· Plants
3. Several
water-transforming & moving processes
· Evaporation
· Transpiration
· Precipitation
· Runoff
XI. Geologic Time and Uniformatarianism
A. The Geologic Time Scale
1. Defined:
A hierarchical time-rock scale in which the 4.6 billion-year
geological/biological history of the Earth is divided into time
units of
varying duration and subdivisions.
2. Development of timescale was a
long, evolutionary process made
by a great number of
individuals working on outcrops scattered far
and wide across the entire
globe.
3. Illustration of the Geologic Timescale (Figure 8.1)
B. Principle of Uniformatarianism
1) Defined: the view that all geological processes that are
occurring today (the rock cycle) were operating in the past,
and
produced similar results throughout Earth's history.
2) "The" guiding
fundamental principle in geology
3) Important implications for
historical geology
XII. Vocabulary Terms
Cold
Accretion theory
Asthenosphere
Atmosphere
Convergent
plate boundary
Core
(inner and outer)
Crust
(continental and oceanic)
Density
Differentiation
Divergent
plate boundary
Geologic
time scale
Geology
Gravity
Historical
geology
Hydrologic
cycle
Hydrosphere
Hypothesis
Igneous
rock
Lithosphere
Mantle
Metamorphic
rock
Mineral
Physical
geology
Plate
Plate
tectonic theory
Principle
of Uniformatarianism
Radioactive
decay
Rock
Rock
cycle
Scientific
method
Seafloor
spreading center
Solar
nebula
Subduction
zone
System
Theory
Transform
plate boundary