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Welcome to Geology
GEO B10
Tuesday, August 26, 2010
• Attendance
• Geology Introduction
Instructor
Jack Pierce
Room DST 118
6:00 – 9:10 pm - Tuesday
What is Geology?
Geo (EARTH ) + logy ( STUDY or SCIENCE )
Study of the Earth
More specifically:


materials that compose the earth
minerals / rocks
processes that shape the earth
volcanoes
rivers
glaciers
earthquakes
Geology is divided into two broad subject areas:
Physical Geology / Historical Geology
Physical Geology:
• understanding the processes on earth below and above the
earth surface and the materials (rocks) involved with these
processes
erosional processes occurring above the
surface
earthquakes occurring below the
surface transferring energy to the
surface
processes below the earth’s
surface that move rigid plate
material on the surface
Historical Geology
• understanding the evolution of the earth and its life forms
from its origins to the present day
• involves investigations into stratigraphy (rock layers), and
paleontology (the fossil record)
layers of rock deposited one layer
over another– preserving evidence
to the origin of the earth
“The rock record”
fossils- preserved animal/plant
remains in the earth’s crust
demonstrating the progression of life
throughout earth’s history
The Geologic Time Scale
• attempts to organize 4.6 b.y.
of the earth history
• created from both relative
and absolute dating processes
Age of
Reptiles
• based on fossil succession and
relative dating principles.
Amphibians
Age of fish
Invertebrates
When does the presence
of man appear on the
geologic time scale?
Humans and Our Earth
How long have humans inhabited the earth?
Jan
Age of
dinosaurs
Jan
4.6 billion years
Man began inhabiting the earth (2 million years
ago) --December 31, the last 30 seconds of the year!!!!
How has man impacted earth in the last 5000
years (the beginning of reasonably modern times)
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Specifically, geology is defined as:
the study of the planet earth--- materials of which it is made,
the internal/external processes that act on these materials
which produce new materials (rock types) and the history of
the planet and its life forms since its origin
Specific disciplines within the field of geology
• Seismology
• investigate the occurrence of earthquakes
• Economic geology
•formation/occurrence of mineral resources
• Volcanology
•investigates volcanoes and volcanic eruptions
• Hydrogeology
• investigation of surface/subsurface water processes
I
geology class
Discuss with a friend:
1. What is the specific definition
of geology?
2. Describe the differences between
physical and historical geology.
I will get an A on my exams and quizzes
How does the view of Earth influence the way we
study earth??
What do you see?
Various “systems” within the earth that interact
with one another -– called Earth System Science
• Systems are NOT individually studied
• How one system impacts another
system
11
Earth as a System: Which system is the Earth?
• How systems exchange matter and energy
SUN
SUN
SUN
Isolated
System
Closed
System
No exchange of
matter or energy
Exchange of energy
but not matter
Open
System
Exchange of both
matter and energy
12
The Fragile Earth – A CLOSED system:
• Any change in a closed system will affect other
systems.
• The amount of matter on earth is “fixed” – “We ain’t got
no more” --- This is all we have.
• When we dispose of waste, it’s still here. The waste will
remain within the closed boundaries of earth.
“There is no away to throw things to.”
13
X
x x
I
this geology class.
Discuss with a friend:
1. Define a system as discussed in
earth science.
2. Differentiate between an open, closed,
and isolated system.
3. Explain why earth is considered a closed
system.
I will get an A on my exams and quizzes.
14
The fragile earth as a closed system is supported by four
interrelated open systems.
Lithosphere
Represents the solid earth:
minerals, rocks, and interior
Biosphere:
Includes all living
organisms on land,
in water, and in air
Atmosphere:
Thin blanket of gas keeping
life alive, warm, and protected
Hydrosphere:
Interaction of all water processes,
only planet with water,
71% ocean 12,500 feet deep,
streams, lakes, groundwater
Geosphere
Interaction of
all open systems
15
Cycles and Interactions Explored in Geology
There are three (3) main earth cycles and within each cycle,
multiple open systems exist.
Hydrologic Cycle
describes the movement of water
through reservoirs of the earth system
(rivers, water vapor, groundwater)
The Rock Cycle
internal/external earth processes
that produce new rock, modifies
rock, transport rock, and breaks
rocks down
The Tectonic Cycle
movement and interaction between
rigid lithosperic plates, internal
earth processes producing divergent,
convergent, and sliding plate motions
II
geology
class
geology class
1. Define the four major open systems and
give an example of how systems may
interact with one another.
2. Define the three major cycles used to
explore geologic processes and give an
example of how these cycles may
interact with one another.
I will get an A on my exams and quizzes
The earth’s place in the solar system
Uranus
Jupiter
Earth
Venus
Mercury
SUN
Mars
Inner planets
Terrestrial planets
Asteroid Belt
8.
Neptune
Saturn
Outer planets
Jovian planets
Gas planets
Low densities
High densities
28
Lithosphere
Cont/ocean crust
Upper mantle
2.8 g/cm3
Crust
Asthenosphere
ductile rock
Mantle -Solid
Si,O,Fe,Mg,Ca
5.5 g/cm3
Mantle
Outer Core
Molten – Ni, Fe
11.5 g/cm3
Core
Inner Core
Solid- Ni, Fe
12.5 g/cm3
Temp:
5000 C
Source of
magnetic
field
Why are densities
arranged from
heavy (core) to
lightest (crust)?
Chemical
Differentiation
29
The earth’s interior
What makes
earth unique??
Oxygen, water, life
• oxygen atmosphere
• no O2 on other planets
• the hydrologic cycle
Soil accumulation
• weathering of rocks
• various soil types
Plate Tectonics
30
• moving continents
• formation of landforms
from interacting plates
Plate Tectonics
• The movement and interactions of large
fragments of earth lithosphere (called plates)
• earthquakes
• new landforms
• volcanoes
• new climatic regions on the earth
• creation of new rock types on the crust
Oceanic Crust
• Thin, dense (Fe, Mg) young rock –basalt
underlying the ocean floor
Continental Crust
• Thicker, less dense (Si,O) older rock – granite
making the bulk of the earth’s land
31
Plate Tectonics!!!
Scientists use fossil evidence,
sea floor evidence, and climatic
evidence to reconstruct the
continents!!!!!!– HOT TOPIC
32
I
Earth Science.
Discuss with a friend:
1. Name the planets in their proper order.
2. Describe the layering of the earth
using lithosphere, asthenosphere,
mantle, and core; explain properties.
3. Describe chemical differentiation.
4. Present at least 3 reasons why the
earth is unique.
I will get an A on my exams and quizzes.
33
Geophilosophical Questions
• Is the Earth old or considered young?
• Are earth process rates rapid or slow?
• How can rock (considered 2-b.y. old) have the
same composition of present rock produced
today?
• If mountains are built through tectonic processes,
why can’t we make obvious observations?
• In terms of geologic time, why is it possible for a
storm to erode 2-million years of rock formation
in a single day?
Historical aspects about geology
There are two schools of thought on the geologic
history and processes that formed our earth.
Catastrophism vs. Uniformitarianism
4
Catastrophism: (mid-1600’s)
powerful geologic events that shape
the earth in a single incident
Volcanic eruptions
Earthquakes
Massive floods
Landsliding
5
Catastrophism: (mid-1600’s)

published by Anglican Archbishop, James
Ussher

determined that earth was only a few
thousand years old – created in 4004 BC

suggested that earth landscapes are
fashioned by great catastrophes – features
form rapidly

an attempt to fit the formation of earth
features into a short amount of time
(6000 years – Biblical philosophy- creationist
6
viewpoint)
Uniformitarianism – Birth of Modern Geology
• “The present is the key to the past.”
Uniformitarianism states:
Physical, chemical, and biological laws that
operate today have also operated in the
geologic past.
Proposed by James Hutton – late 1700’s
• argued using the “rock cycle” concept
• argued using earth processes that can
be observed
• What is required? TIME
7
The Uniformitarianism philosophy
Do geologic processes act slowly or rapidly?
How many catastrophic events take place/day?
When was the last major volcanic eruption?
When was the last major earthquake?
How long does it take a river to carve a canyon?
How fast are the continents moving?
Do you consider yourself a catastrophist or a
uniformitarianist?
8
Taking Uniformitarianism literally – Problem with “U”
Rates and intensities of geologic processes change
over time.
Example:
10,000 years ago, large land masses were covered in
ice.
Different type of geologic environment than today
Different intensity
Different rates of erosion
Given the concept of Uniformitarianism, would you
consider the earth to be very OLD or very YOUNG?
9
I
geology class.
Discuss with a friend:
1. Describe the differences between
catastrophism and uniformitarianism.
2. Provide at least 2 examples each of
catastrophism and uniformitarianism.
3. Identify “problems” with both philosophies.
I will get an A on my exams and quizzes.
10
Why do we care and study our earth (geology)?
Earth resources:
• societies depend on minerals and rocks for material
resources
• soils that produce agriculture products
• the availability of fresh water for everyone
Geologic hazards:
• volcanic eruptions, landslides, earthquakes, floods
(when does nature become a geologic hazard?)
The uniqueness of earth
• constant fascination and can give one geologic chills
• earth processes may open the door for other planetary
processes
Students need the science requirement
for their degree!