Transcript Introduction to Geology

ESCI111: Introduction to Physical Geology
& Physical Geography
Dr. Francis O. Odemerho
Alumni Hall, Room 1402
Tel: (618) 650-2097
Email: [email protected]
Website: http://www.siue.edu/~fodemer/esc111.htm
Topic 1: Introduction to Geology

GEOLOGY: THE SCIENCE OF EARTH
- Physical and Historical Geology
- Importance of Physical Geology
 THE DEVELOPMENT OF GEOLOGY
- Catastrophism
- Uniformitarianism
- Modern Geology
- The Magnitude of Geologic Time
 THE NATURE OF SCIENTIFIC INQUIRY
- The Goal of Science
- The Scientific Method
 EARTH AS A SYSTEM
- Hydrologic Systems
- Tectonic Systems
Topic 1: Introduction to Geology

THE SOLAR SYSTEM
- Composition of the Solar System
- Terrestrial Planets
- Unique Features of Terrestrial Planets
- Jovian Planets
- Features of Jovian Planets
- The Moon of Planet Earth
 EARTH’S SPHERES
- Atmosphere
- Hydrosphere
- Biosphere
- Lithosphere or Geosphere
GEOLOGY: The science of Earth
 Geology
is the scientific discourse of planet
Earth
 It is divided into 2 broad areas:
 Physical Geology:
- examines the materials making the earth
- and geologic processes operating on or
beneath the earth surface
 Historical Geology:
- chronology of geologic events
- focuses on asking the when questions
Sub-fields of Geology
Planetary Geology
Geomorphology
Seismology
Geophysics
Oceanography/Ocean Science
Environmental Geology
Economic Geology
Petrology
Geochemistry
Mineralogy
Tectonics
Paleontology
Paleogeography
Stratigraphy
Geochronology
Archeological Geology
Biogeosciences
Engineering Geology
Forensic Geology
History of Geology
Structural Geology
Glacial Geology
Hydrogeology
Medical Geology
GEOLOGY: Subfields and Related Disciplines
Two Broad Fields of Geology
Physical Geology
Historical Geology
Geomorphology
Seismology
Geophysics
Oceanography
Environmental Geology
Economic Geology
Paleontology
Paleogeography
Stratigraphy*
Geochronology
Petrology
Geochemistry
Mineralogy
Structural Geology
Glacial Geology
Importance of Physical Geology

Meets SIUE general education requirement

Helps our understanding of nature and how the
earth works

Helps us in the discovery of earth’s natural resources:
- water and soil resources
- mineral ores and deposits
- building materials
- oil fields for fossil fuels (Petroleum, Coal and
Natural Gas), etc, etc
Importance of Physical Geology

Offers us key information on the causes and effects
of past climatic changes

Increases our environmental awareness and the
recognition of potential geologic hazard zones

Serves as useful guide in planning construction
works, environmental planning and management
THE DEVELOPMENT OF GEOLOGY

Writings about earth’s materials and processes
started more than 2300 years ago, among GrecoRoman scholars

Aristotle believed that:
- rocks were created under the influence of stars
- earthquakes were caused by over-pressured
ground air that escaped rapidly when heated up
by central fires

Aristotle’s authoritative posture thwarted the
growth of geologic sciences
THE DEVELOPMENT OF GEOLOGY

School of Catastrophism:
- Archbishop James Ussher in the mid-1600
claimed that the earth was created in 4004 B.C.
-
This means that the earth is only 6000 years old
-
This meant that all geologic structures were
formed very rapidly within the last 6000 years
rather than millions of years expected by
geologists
-
Such short earth history gave rise to the school
of catastrophism that dominated geology during
the 17th and 18th centuries
THE DEVELOPMENT OF GEOLOGY
-
Catastrophists believe:
=>
that landforms are produced by great
catastrophic events that are no longer in
operation today
=>
that features such as mountains and canyons
were produced by sudden and often
worldwide disasters like the Noah’s flood
=>
in divine intervention and creationism in
geology
THE DEVELOPMENT OF GEOLOGY

School of Uniformitarianism:
- is to counter the teachings of the school of
catastrophism by James Hutton in his book
“Theory of the Earth” in the late 1700s
-
He argued that the Earth has a long history with
no vestige of a beginning & no prospect of an end
-
He argued that physical, chemical & biological
laws that operate today also operated in the
past (i.e. the present is the key to the past)
-
And that landforms are produced by geologic
processes that act slowly and steadily (or
uniformly) through time
THE DEVELOPMENT OF GEOLOGY
The Birth of Modern Geology:
- John Playfair and Charles Lyell made the doctrine
of uniformitarianism to be accepted by the
scientific community and helped to remove
religion from geology
-
The Exploration of American West in the mid –
1800s laid the foundation for the development of
modern geology
-
William Morris Davis in late 19th century
synthesized the concepts developed by the
explorers to develop his erosion cycle of erosion
THE DEVELOPMENT OF GEOLOGY
Magnitude of Geologic Time:
 Geologic time scale is developed using two basic
methods:
- Relative Dating Technique and
- Absolute (Radiometric) Dating Technique

Relative dating involves the placement of rocks in
their proper sequence of formation (no actual age)
using simple principles like:
- superposition and original horizontality
- fossil succession and
- cross-cutting
Geologic Time
Geologic Time
Magnitude of Geologic Time

Geologists worldwide built the standard geologic column of
earth history using relative dating technique

The Geologic time scale is divided into two major Eons:
-
Phanerozoic (visible life) Eon (0 – 542 million years ago)
-
Precambrian Eon (542million – 4.5 billion years ago):
-
Proterozoic (542million - 2500million years ago)
(First Multi-celled organisms)
-
Achaean (2500million – 4000million yrs ago)
(First One-celled organisms)
-
Hadean (4000million – 4500 million years ago)
(First One-celled organisms)
Magnitude of Geologic Time

The Phanerozoic Eon of time is divided into three major
Eras:
-
Cenozoic Era
Mesozoic Era
Paleozoic Era

The Precambrian Era accounts for 88% of geologic time

Absolute dating determines the actual age of rocks using
radiometric methods

The Earth is about 4.5 billion years old
The Nature of Scientific Inquiry
The Goal of Science:
 Science is based on the assumption that nature is
orderly, consistent and predictable

Therefore, the goal of science is to:
-
discover the underlying pattern in nature
make general verifiable statements of
relationships in nature
make predictions about what to or not to
expect about nature
The Nature of Scientific Inquiry
The Scientific Method:
 To achieve this goal, scientists make observations
and collect measurable facts that help to explain any
observable relationships in nature

How and why things happen is explained using:
- hypothesis which is a tentative or untested
relationships or explanations
-
theory which is a well tested and widely
accepted view that the scientific community
agrees that it best explains the observed
relationship or facts
The Nature of Scientific Inquiry

Hence, the scientific method involves:
-

the formulation of some form of hypothesis
the collection of data through observation and
measurement
testing the data through some form of scientific
analysis to see if the data supports the initial
hypothesis
However, some scientific discoveries may occur
through logical reasoning alone, like in
mathematics
The Nature of Scientific Inquiry

Once an hypothesis survives extensive scrutiny, it
is elevated to the status of a theory

Paradigm – a theory that is held with a very high
degree of confidence because it explains a large
number of interrelated aspects of the natural
world
EARTH AS A SYSTEM

The earth (geologic) is a natural system in
continuous motion

Geologic systems governed by natural laws
increase our understanding how planet earth
works

Geologic systems help us to understand:
- geologic change and their effects
- geologic processes
- structural features of our planets
EARTH AS A SYSTEM

A system is a set of interdependent objects or
materials that work together with energy as a unit
or a unified whole

A system helps us to understand how rainfall,
runoff, landforms are related and function
together as a unit

Natural systems are of two types:
- Closed system (exchanges only heat, no new
matter) (Example: cooling lava flow)
- Open system (exchanges both heat and materials)
EARTH AS A SYSTEM

Most geologic systems are open systems because
energy and matter flow freely across system’s
boundaries (Example: river system with rainfall from
outside)

The river system receives matter like rain & snow
from outside the system (input) and flows out of the
system to the ocean (output)

It utilizes gravitational energy and kinetic energy
and solar energy from the sun
EARTH AS A SYSTEM

In general, geologic systems involve the flow of
energy and the movement of matter

The transfer of matter and energy causes the
system to change in order to establish a state of
Equilibrium within the new surroundings

Two major subsystems of the geologic systems
include:
- The Hydrologic System
- The Tectonic System
EARTH AS A SYSTEM: Hydrologic System

It is a geologic system showing the pathways of water
moving from:
- the oceans
- to the atmosphere
- over the continents, and
- back to the oceans

The flow of water across earth surface causes
erosion, transport and deposition of sediments

Major subsystems include:
- Atmosphere-Ocean system, River systems
- Glacial systems, Groundwater systems
- Shoreline systems and Eolian (wind) systems
EARTH AS A SYSTEM: Hydrologic System
EARTH AS A SYSTEM: Hydrologic System
THE SOLAR SYSTEM
Composition of the Solar System - it consists of:
 The sun (center of the solar system) and eight
planets

Four inner planets of the solar system are called
terrestrial planets: (Mercury, Venus, Earth and
Mars)
THE SOLAR SYSTEM

>10,000 asteroids (asteroid belt between Mars and
Jupiter)
An Asteroid With Impact Craters
THE SOLAR SYSTEM

meteorites (pieces of rocks and minerals frozen in
gases)

Hale-Bopp Comet seen (1997) with long glowing tail
due to ice vaporization
THE SOLAR SYSTEM

natural satellites or moons (>64 moons)

all the planets formed same time from same general
materials and move counterclockwise in an elliptical
orbit around the sun
THE SOLAR SYSTEM


Pluto is no longer regarded as a planet of the solar
system
THE SOLAR SYSTEM

Pluto is not part of our solar system because of:
- its unique oblique orbital plane and
-
its relatively higher density, given its location
THE SOLAR SYSTEM

This is the current composition of the solar system

All planets orbit in the same plane as the sun’s
equator
THE SOLAR SYSTEM: The Nebula Theory

The Nebula theory is the most accepted explanation
of how the solar system is formed

According to the Nebular hypothesis:
-
solar system evolved from rotating cloud of dust
and gases called nebula
-
nebula contained mainly hydrogen and helium
produced by the Big Bang
-
nebula began to contract at about 5 billion yrs
ago
THE SOLAR SYSTEM: The Nebula Theory

According to the Nebular hypothesis:
-
nebula became flat and disk-shaped with the
protosun at the center
-
inner planets began to develop from condensed
rocky and metallic clumps with high melting
point
-
strong solar winds removed the lighter gases like
hydrogen and helium from the inner planets
THE SOLAR SYSTEM: The Nebula Theory

According to the Nebular hypothesis:
-
larger outer planets began to form from the
lighter gases with a high percentage of
ices or frozen gases – water, carbon dioxide,
ammonia, and methane
Glowing nebular clouds of gases and dust
particles become concentrated to form stars
Nebula contracted into a rotating
disk and heated up as
gravitational energy converts into
heat energy
Gravitational collapse of nebula
causing its inward contraction
Cooling nebula condenses
to form tiny rocky and
metallic solid particles
Collision of dust-size particles join to
form asteroids and accrete to form
the planets
THE SOLAR SYSTEM: Terrestrial Planets

Terrestrial planets: Mercury, Venus, Earth & Mars

Composed of minerals and rocky materials

more dense (>3gm/cm3)

Less oblate in shape (more nearly spherical)

Slower in rotation and Smaller in size

Diverse and shallow atmosphere
Common Features of The Planets
Planets
Rotation Time
Equatorial
Mean Density
Diameter (km)
(Days)
(g/sq. cm)
TERRESTRIAL PLANETS
Mercury
Venus
Earth
58.7
243
1
4,880
12,104
12,760
5.43
5.24
5.52
Mars
1.03
JOVIAN PLANETS
Jupiter
0.41
Saturn
0.43
6,787
3.98
142,796
120,660
1.33
0.69
Uranus
0.72
51,200
1.27
Neptune
0.67
49,500
1.76
6.39
2,300
2.03
OTHER PLANETS
Pluto
THE SOLAR SYSTEM: Jovian Planets

consist of: Jupiter, Saturn, Uranus Neptune

much larger in size

composed entirely of gases and less dense

much more oblate and rotate more rapidly

dense and turbulent atmospheres
THE SOLAR SYSTEM:
Unique Features of Planet Earth
 organized
into four spheres: (atmosphere,
hydrosphere, biosphere and lithosphere)
 appropriate
temperature for water to exist as
solid, gas and liquid
 biosphere
and hydrosphere unique to earth
THE SOLAR SYSTEM:
Unique Features of Planet Earth
 earth’s
surface is dynamic (continuously
changing) because of:
- movement of materials powered by high
internal heat
- movement of surface water and winds
powered by solar energy
 atmosphere
is 78% nitrogen and 21% oxygen
THE SOLAR SYSTEM: Earth’s Moon

No atmosphere, No hydrosphere, No biosphere

Densely cratered highlands called Terrae

Lava plains called Maria (fewer craters) is basalt

Craters formed 4.5 billion years ago but still
undeformed
THE SOLAR SYSTEM: Earth’s Moon
THE SOLAR SYSTEM: Earth’s Moon

Lunar geologic history:
- initial period of intense meteorite bombardment
- period of volcanic activity
- later period of light meteorite bombardment
- undeformed by internal forces
- undeformed by wind, water, and glacier
THE SOLAR SYSTEM: Earth’s Moon
THE SOLAR SYSTEM: Luna Time Scale
EARTH’S SPHERES: Atmosphere

It is the envelope of gases held in place by
gravity

Dominant gases by volume of dry air:
- Nitrogen (78%)
- Oxygen (21%) (no in earliest atmosphere)
- Argon (0.93%)
- Carbon Dioxide (0.03%)
(used to be more but reduced due to the
formation of limestone in the oceans)
- water vapor (0-4%)

It extends up to 6000 miles but 97% of
atmospheric gases found within 18 miles
The Planet Earth
EARTH’S SPHERES: Atmosphere


Thermal layers of the atmosphere
- Troposphere (0-13 km) (weather belt)
- Stratosphere (13-55 km) (ozone layer)
- Mesosphere (55-80 km)
- Thermosphere (80-210 km)
- Exosphere (>210 km)
Most weather phenomena occur in troposphere
 The major wind systems of planet earth are:
Lat 0o – lat 30o
Trade Wind Belt
Lat 30o – lat 60o Westerly Wind Belt
Lat 60o – lat 90o Polar Easterly Wind Belt
Thermal Layers of Earth’s Atmosphere
EARTH’S SPHERES: Hydrosphere

All water bodies including:
- ocean water 97%
- Ice/glacier 2.15%
- Groundwater 0.62%
- Saline lakes & inland seas 0.008%
- Freshwater (lakes & streams) 0.009%
- 71% of earth surface is water
 Evolution of life is because of the presence of
water
 Water moves from ocean-atmosphere-land-ocean
to form the hydrological cycle
 Sequence of operation of the cycle involves:
evaporation-condensation (cloud formation)precipitation-runoff
Earth’s Atmosphere Compared
EARTH’S SPHERES: Hydrosphere

Hydrological cycle is powered by solar energy
 Glacier locks up water on land and breaks the
cycle
 Components of the hydrological cycle:
- River systems: collect surface runoff and
groundwater, hence stream valleys are the
most abundant landform on earth
-
Groundwater systems: water moving slowly
through pore spaces and capable of
dissolves soluble rocks to form caverns in
Karst regions of Monroe County in Illinois
and Mammoth Cave in Kentucky
EARTH’S SPHERES: Hydrosphere
-
Glacier systems: Pleistocene glacier occurred
covered much of North America and Europe
with ice sheets about 15,00 years ago.
Antarctica Continental glacier is 2.0-2.5 Km
thick and covers 13 million Sq. Km. Today,
2% of earth’s total water is glacier
-
Shoreline systems: areas affected by wave
action and produce wave-cut cliffs, terraces,
delta, beaches, bars, and lagoons.
-
Wind systems:
EARTH’S SPHERES: Biosphere








The world of all plants and animals
1.75 million species already described
>13 million species estimated
Today’s species represent only 10% of species that
ever lived
15-20% of all species would be extinct by the
beginning of the 21st century
Marine organisms form exoskeletons and shells from
seawater
They also form fossil fuels and beds of limestone
Preserved as fossils and help to reveal earth history
EARTH’S SPHERES: Geosphere

The geosphere is the solid earth extending from the
surface to the center of the planet (about 6400km)

Its outermost solid layer is called the lithosphere
and about 70-100 km thick

It is broken into lithospheric plates made up of
seven major plates and about a dozen minor plates

lithospheric plates moved by convection currents
Earth’s Lithospheric Plates
Earth’s Lithospheric Plates
Review Questions (Topic 1)
1.
What are the basic differences between the disciplines of physical
and historical geology?
A. Physical geology is the study of fossils and sequences of rock
strata; historical geology is the study of how rocks and minerals
were used in the past
B. Historical geology involves the study of rock strata, fossils, and
geologic events, utilizing the geologic time scale as a reference;
physical geology includes the study of how rocks form and of
how erosion shapes the land surface
C. Physical geology involves the study of rock strata, fossils, and
deposition in relation to plate movement in the geologic past;
historical geology charts how and where the plates were moving
in the past
D. None of the above – physical geology and historical geology
are essentially the same
Review Questions (Topic 1)
2. Compared to the age of Earth accepted as correct today, how did 17th
and 19th century proponents of catastrophism envision the Earth’s age?
A. They believed Earth to be much older than current estimates
B. They believe it to be about the same as current estimates, give or
take a few million years
C. They believed Earth to be much younger than current estimates
D. None of the above – they didn’t really address the age of Earth
3. ________ was an important 18th century English geologist and
proponent of uniformitarianism.
A. Charles Lyell
B. Isaac Newton
C.
James Hutton
D. James Ussher
4. The currently accepted age of Earth is ______ years.
A. 4.5 thousand
B. 6.1 trillion
C.
4.5 billion
D. 6.4 million
5. The ____ division of the geologic time scale is an era of the
phanerozoic eon.
A. Paleocene B. Paleozoic C. Permian C. Proterozoic
Review Questions (Topic 1)
6.
The ____ forms the relatively cool, brittle plates of plate tectonics.
A. Asthenosphere
B. Lithosphere
C.
Eosphere
D. Astrosphere
7. All of the following are possible steps of scientific investigation
except for _____.
A. The collection of scientific facts through observation and
measurement
B. Assumption of conclusions without prior experimentation or
observation
C. The development of one or more working hypotheses or models
to explain facts
D. Development of observations and experiments to test the
hypothesis
8.
The ____ refers to the total of all life on Earth.
A. Hydrosphere
B. Atmosphere
C.
biosphere
D. asthenosphere
Review Questions (Topic 1)
9.
A ____ system is one in which energy moves freely in and out, but no
matter enters or leaves the system.
A. Closed
B. Open
C. Feedback D. Equilibrated
10. _______ is often paraphrased as “The present is the key to the past.”
A. Biblical prophesy
B. Uniformitarianism
C. Catastrophism
D. Aristotelian logic
11. ______, a popular natural philosophy of the 17th and early 18th centuries,
was based on a firm belief in a very short geologic history for Earth.
A. Ecospherism B. Exoschism
C. Uniformitarianism
D. Catastrophism
12. The ________ proposes that the bodies of our solar system formed at
essentially the same time from a rotating cloud of gases and dust.
A. Big Bang theory B. Plate tectonics
C. Nebula hypothesis
D. Heliocentric theory
Review Questions (Topic 1)
13.
14.
15.
16.
17.
The doctrine of uniformitarianism implies that the current forces and
processes shaping the earth have been operating for a very long time.
A. True
B.
False
The currently accepted age of Earth is approximately 4.5 million
years.
A. True
B.
False
A scientific theory is a tentative or untested explanation that is
proposed to explain scientific observations.
A. True
B.
False
In an open system both energy and matter flow into and out of the
system.
A. True
B.
False
According to the nebular hypothesis, all the bodies in the universe
evolved from a rotating cloud of gases and dust about 5 billion
years ago
A. True
B.
False