A! a practice of gaining knowledge of nature through the scientific method

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GEO 1404 Study Guide: Owen

CHAPTER 1, 2, & 4: INTRODUCTION, EARLY WORKERS, BASIC PRINCIPLES, GEOLOGIC TIME, & RATES OF CHANGE (All references in this study guide to text figures & pages are to: Prothero & Dott, 2004, Evolution of the Earth, 7th, edition. ISBN 0-07-252808-7). Key figures: 2.9, 4.3, 4.6, 4.11, 4.12, 4.13, 4.14, 4.17, 4.21, 4.22


A. Historical Geology (GEO 1404): evolution of Earth (& other planets & moons) & its (their) inhabitants

1. Concerned with past:

a. processes (plate tectonics, evolution of life, etc.)

b. geography (continent/ocean distribution, biogeographic zones, etc.)

c. events (mountain-building, erosional intervals, evolution of new life forms, mass extinctions, etc.)

2. Based on knowledge of Physical Geology (GEO 1403, the prerequisite): dealing with present Earth:

a. materials

b. structure and landforms

c. internal & external processes

3. Both physical & historical geology tied together by plate tectonics, the unifying theme

4. But, the evolution of life, especially as revealed by fossils, is an added, integral theme of historical geology

5. The scientific method is universally used in all work in the natural sciences (physics; chemistry; biology; geology; astronomy).

Q? What is natural science?

A! A practice of gaining knowledge of nature through the scientific method, consisting of the following steps

1. Ask a question about nature

2. Collect data (facts) relevant to the question through observation or experimentation 

3. Suggest possible explanation(s) (hypothesis, either single or multiple) 

4. Test hypothesis (should be reproducible; confirmed by other scientists

5. Accept, reject, or modify hypothesis (may need new hypothesis & retest). If confirmed, may lead to a descriptive generalization (law).

6. Formulate general theory (cannot prove a theory; can only disprove a theory!). Theory may be called principle.

Establish the theory by exhaustive, successful testing against all competition by scientific community.


FACT: Facts are confirmed observations. They may not tell you how something works, but they are a repeatable observation (Such a fact could be that a certain ruler is 12 inches in length, no matter who measures it or how many times it is measured). Facts can change when better data is available (For example, a fact for many years was that humans had 22 pairs of chromosomes, but modern instruments and advances in microbiology now yields the fact that there are 23 pairs).

HYPOTHESIS: A hypothesis is a tentative statement of the relationship among things. Most take the form of “If…then…” (For example, if brightly colored male guppies are more likely to attract predators, then they will be less abundant in environments with high predation rates). Hypotheses can be tested and proven to be correct or incorrect (For example, if levels of lead in the blood of children are higher in children with lower IQ scores, then children in environments with high lead levels should have lower IQ scores). Statistics and probability are important components of hypothesis testing.

LAW: A scientific law is a descriptive generalization (Newton’s laws of gravity, etc.), but exceptions may occur under certain conditions, such as in a vacuum (For example, the Law of Superposition states that, in a pile of sedimentary rock layers, the oldest (first deposited) are on the bottom and the youngest (last deposited) are on the top; however if tectonic movements have turned the pile of rocks upside-down, the law is not true. Another use of the word, law, in science is for an old, well-tested theory.

THEORY: In science, a theory is a logically constructed, well tested set of scientific facts, laws, and confirmed hypotheses that explains a natural phenomena. It is not a guess, hunch, or opinion, such as the word may be used in a non-scientific sense. Scientific theories may be modified as new facts, laws, or confirmed hypotheses are discovered. These changes typically involve the details, not the central premise of the theory. Examples of theories include magnetism, evolution, chemical bonding, uniformitarianism, radioactive decay, the big bang, etc.

Science is based on physical evidence, not authorities, spirits, astrology, luck, or dreams

Science is based on reality, not abstractions, beliefs, philosophy, religion, or political correctness

Q? Name a current scientific issue that is blinded by social, religious, or political behavior of humans?

A! ___________________________________________________________________Name a bunch more!

Some things masquerade as science, for example, “Creation Science” is not science because it does not follow the scientific method. It starts with the answer (“Theory”) from an authority (Bible), then looks for selected “evidence”, much of which may not be real or physical, to support the pre-selected answer! This is the reverse of the scientific method, also known as a form of pseudoscience. Intelligent design, a new variation of Creationism that purports to be independent of religion, is based on intentional ignorance and defeatism instead! It is an attempt to find a legal form of creationism without mentioning god.

Null hypothesis is often used in science. This consists of actively seeking evidence to contradict what we would most like to believe. It works like the process of elimination. Its use helps scientists remain honest and not follow the usual human tendency to look for confirmation only. Science often advances by elimination of possible explanations as well as by validation of possible ones. The null hypothesis is not used by creationists.

Parsimony is a common practice in science. It is the tendency to assume the simplest explanation of an observation first because this has been shown to be true in nature in most cases. An oversimplified explanation may lead to a better, complex explanation, which may be a combination of simple explanations. Intelligent design employs the opposite of parsimony by assuming that organisms are too complex to have evolved naturally, so there must have been a designer. Occam's Razor, the deduction that it is more plausible for an unknown phenomena to be of natural, but unknown, origin rather than unnatural (extraterrestrial; supernatural; etc.) origin, commonly accompanies parsimony. Extraordinary claims, such as religious miracles that defy natural laws, require extraordinary proof!

Skepticism is valuable in science. The scientific method has taught us to discount pat answers to questions about nature and closely examine the data that purports to lead to the answer. Skeptical inquiry has led to discrediting many pseudoscientific practices and events, such as astrology, water-witching, UFOs, mythical beings ("Big Foot", etc.), religious miracles, paranormal hoaxes, psychics, cults, etc. Cynicism is not skepticism.

Science versus Religion (from Pazameta, 1999, Skeptical Inquirer, v. 23, no. 4)

1. Science and religion are mutually exclusive and complementary aspects of human epistemology; each deals with a separate domain of human experience.

a. Science deals with the natural universe (which really exists). Religion deals with the supernatural (spiritual)
universe. The supernatural does not exist in a physical sense.

b. If both science and religion keep within their parts of the universe, no conflict could possibly exist. A person,
for example, can be both a scientist and a Buddhist. However, both stray into the other's universe, so
conflicts result.

2. Pseudoscience: a mixture of science and religion (selective reasoning plus faith), that produces unproven,
untested, or disproved statements about nature based on faith alone. Examples:

a. "Proof" that the accused is a witch.

b. Scholarly analyses of scriptures that "prove" one set of beliefs superior to another, and that only its adherents

can attain salvation.

c. "Proof" that one ethnic group is superior to another.

d. "Evidence" that ancient astronauts visited Earth.

e. "Evidence" that the origin of species lies in contemporaneous divine creation.

f. "Tests" that show that this herbal concoction or that crystal pendant can cure cancer or whatever.

g. "Scientific tests" to "prove" spiritual existence after death, the existence of God(s), etc.

3. Proof in religion and science:

a. Proof in religion is impossible--it is replaced by faith. Either you believe a doctrine or you do not--this is the
only "test" for a religious doctrine. Some religious beliefs are logical, but logic does not prove the belief.

b. Proof in science consists of putting the question to nature, by observation or experimentation. Faith in the
answer is irrelevant, because a scientific hypothesis either passes the tests or does not. Scientific proof
is contingent on an objective natural world and not upon subjective interpretation (philosophical proof).


1. How do we reconstruct geologic history?:

a. Observe Earth as we find it today (rocks, fossils, structures, etc.), & use scientific method to discover where, when, & why these Earth features formed

b. Work from the present Earth (that is all we have!) & look back into the past, to reconstruct the past Earth from evidence we find in the rocks of today’s Earth

c. We go a long time back into the past, because Earth is 4.5 billion years old! Ga = billion years ago.

1) Oldest dated Earth rock is 4.0 billion (4,000,000,000) years old (zircons in gneiss from Canada)

2) Oldest dated Earth mineral is 4.3 to 4.4 billion years old (zircons in sandstone from Australia)

3) Oldest dated moon rocks (4.2 billion years old) and meteorites (4.6 billion years old). These rocks should have existed on Earth too, but have been recycled by plate tectonics in a dynamic Earth. Moon is static, except for impacts.

4) Human life expectancy (75 y.) is 1.6 millionth of earth age (0.0000016 %)!

5) Vast time (millions to billions of years) is unique to geology and astronomy

2. Basic principles of historical geology are derived from three fields of geology:

a. Stratigraphy (study of time/space relationships in rock record)

b. Sedimentology (study of processes that form sedimentary rocks)

c. Paleontology (study of fossils).

3. All fields of science depend on one another to some extent. This is especially true of geology, which is heavily dependent on physics and chemistry principles and, in the case of fossils, formation of limestones, etc., on biology. Astronomy also plays a role, especially in early Earth history, impact events, etc.

4. No amount of money or expertise can guarantee a breakthrough in a given field of science within a given time frame. In scientific research, there are no answers in the back of the book, no ways of knowing which areas of investigation will be fruitful and which will be dead ends. We understand basic science fields better than geology.

5. Science is aided by technology, but technology is not science. Science is knowledge of the laws of nature; technology is the application of this knowledge to production of material devices and products. Such devices based on physical or chemical principles may aid other sciences such as geology.


Geologic Time - It is difficult for humans, because of our brief life-span & history, to conceive of the immensity of geologic time (4,500,000,000 years) on Earth. Human life expectancy (75 y.) is 1.6 millionth of Earth age (0.0000016 %)! Ex.: 1 year is 1/4,500,000,000 of Earth history; this semester (0.4y) is 0.4/4,500,000,000 or 1/11,500,000,000 of Earth history. During a regular semester, you will learn 4,500,000,000 years of Earth history in one semester! This averages ~300,000,000 years per week. For a summer session, this averages 900,000,000 years per week.

Rates of geologic change: See text p. 4-13. The popularity of Catastrophism among early geologists is understandable because of the human tendency to notice sudden, dramatic changes (volcanic eruptions; earthquakes; floods; tsunamis), but not gradual, subtle ones (sea-level change; land uplift & subsidence; erosion). The vast majority of geologic processes are very slow. Even sudden events that appear infrequently on a human time scale, for example, a 500-year frequency flood, may be a very frequent event on a geologic time scale, but a rare event on a human time scale. Geologic changes may be classified into:

1. Linear (constant rate of change) versus nonlinear (see text Figures 1.11 & 1.12). In nature, linear change is rare.

2. Repeating versus nonrepeating (periodic or rhythmic).

3. Repeating events may be either irregular (episodic) or regular (periodic or rhythmic), at a recurring time period

Geologic time scale (see attachment): YOU ARE RESPONSIBLE FOR LEARNING THIS ENTIRE CHART: ALL CATEGORIES, NAMES, AGES, & SPELLINGS. ALL OR PARTS OF IT MAY BE ON THE FIRST & LATER EXAMS! Be sure to capitalize all names because they are formal, as your names are.

Note: most recent is at the top; oldest is at the bottom. Why? Because this conforms to an undisturbed succession of rocks! See Superposition above. Learn the chart from the bottom to the top (in actual time order), in the order that the history occurred (not in reverse order).

A. Eons: largest division of geologic time

1. Phanerozoic Eon (542 Ma - present). Ma = millions of years before present.

a. “visible” life

b. before “visible” life is all other geologic time, Cryptozoic Eon = “hidden life” (4.5 Ga-0.542 Ga)

c. Cryptozoic is also known as “Precambrian”, which is more commonly used than Cryptozoic

2. Precambrian is subdivided into:

a. Proterozoic Era (2.5 - 0.542 Ga). Ga = billions of years before present.

1) Ediacaran Period has recently been accepted for latest Proterozoic time (630-542 Ma). Other periods are proposed for rest of Proterozoic.

b. Archean Era (4.0 - 2.5 Ga, approximately

c. Hadean Era (4.5 - 4.0 Ga, approximately

1) a little-used term for the time interval of which we have little or no record on Earth

B. Eras: next smaller division of geologic time; for the Phanerozoic they are:

1. Paleozoic (542 - 251 Ma)

a. “ancient” life

2. Mesozoic (251 - 66 Ma)

a. “middle” life

3. Cenozoic (66 Ma - present).

a. “recent” life
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