HISTORICAL GEOLOGY UNIT 1 LECTURE AND STUDY GUIDE
HISTORICAL DEVELOPMENT of GEOLOGIC PRINCIPLES
(Revised 7/16)
UNIT 1: VIDEO HIT HOMEWORK; Write a minimum of two paragraphs with minimum of three
sentences each for the unit video site
For any Unit Web Hits and Unit Web Videos, go to the “DMC HOME” website; in Search box –type “Geology”,
select “Vernon Kramer”, scroll down to GEOL 1304, select “Syllabus”, select “Video Web Hits”, click on icon for web
site
OR: go to DMC Home website, select “Degrees, Certificates, Courses”, scroll down to Natural Sciences and select
“Geology”, select “Faculty Listings”, select “Walter Vernon Kramer”, find “Geol 1304”, select “Syllabus”, and there
you can find the video hits”, click on icon of interest for video site
[IF NONE OF THE WEB SITES COME UP, YOUR COMPUTER PROBABLY NEEDS TO BE REBOOTED (RESTARTED)
Some Geology Definitions
- Geology is the science that studies the Earth, as well as other planets.
- Geology concerns all aspect of Earth, including its origin, history, rocks and minerals, processes and
dynamics of how the Earth changes over time.
- Every aspect of geology has some economic and environmental relevance.
- Physical Geology: study of rocks and minerals as well as the processes that operate on the Earth’s
surface (various components of the hydrologic system) and within the Earth (various components of
the tectonic system)
- Historical Geology- (Earth History) examines the origin and evolution of Earth, its continents,
oceans, atmosphere and life (biota) as preserved in rocks and minerals
- Historical Geology is more concerned about the history of Earth and the history of life (biota) on
Earth
A Short Overview of pre-Modern Geologic Concepts
- Earliest man could have noticed lava rocks in some areas, sediments in other areas and layers of hard
rocks almost everywhere. He probably was not able to explain changes caused by earthquakes,
flooding, sandstorms, etc.
-The concepts of geological principles and related (geological) time were alien to most throughout
early human history.
Prehistoric Geologic Concepts
- Any thought about geological processes and principles would have been very narrow and focused for
those living in the prehistoric world.
- Earth processes and changes would have been measured by changes associated with climate and
seasons, with changes in the lengths of day and night, with birth and death cycles or sudden natural
disasters.
- Also, there was no scientific data available upon which to estimate the time needed for any Earth
processes.
- Usually supernatural causes were attributed to many unexplained natural events. Do you think that
this would have been different for you?
CLASSROOM EXERCISE – How would you define geologic artifacts at this time in the past?
-With our group exercises, we have assumed that Earth and man were created at nearly the same time
(a false assumption).
- Earth has been here for more than 4.5 billion years and life on Earth did not arrive for some time.
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- Another exercise along with three short video clips from “Origins”.
- VIDEO: Origins
It is never too late to be what you might have been.
Let’s start with the following timescale:
2 M BC___________180,000 BC_____________3300 BC_____900 BC_____500 BC _____350 BC
Prehistoric Mineral Mining and Geology
- The first rocks and minerals to be used were those basically lying on the surface of the Earth. The
earliest discovered simple use of stone by man creatures began more than 2 million years ago.
- The first evidence of sophisticated use of stone (Stone Age) was already in use by 180,000 years ago.
- Gold was used by 4700 BC. By 3300 BC, man had discovered that melting tin and copper ores
produced bronze. In different parts of the world the use of copper and iron (1200 BC) evolved.
Surprisingly, mining of minerals began long before the study of geology.
Early Eastern World Geologic Concepts
- For the ancient Brahmins of India (900 BC): time was eternal; there was little reason to study
geologic changes
- From the early Eastern world, we have few records of geologic studies.
Early Greek Geology Concepts
- The ancient Greeks are often credited for the beginning of scientific thought in the Western world.
- For example, Herodotus (500 BC) recognized fossils as forms of ancient life.
- Aristotle (350 BC) used simple observations and logic (but no experiments) and resolved scientific
issues with “pronouncements”. “After some observations, man could solve all natural mysteries with
pure thought and logic”. Aristotle’s pronouncements would set back geologic sciences for centuries.
Don't let what you can't do interfere with what you can do.
Let’s continue with the following timescale:
______50 AD______132 AD________ 500 AD_________1000 AD_______1200 AD____1500 AD
Other Historic Geologic Concepts (pre-modern)
- The Romans did little to advance geologic sciences, although they worked many mines for minerals
and metals.
- The Roman - Pliny the Elder (50 A.D.) - attributed fossil shark teeth as “tongue stones” that fell to
Earth during lunar eclipses. However, he did recognize that amber was derived from fossilized tree
sap and devised a system to classify mineral crystals.
A “tongue stone”
- The Chinese in 132 AD had developed a workable earthquake detector.
- The fall of the Roman Empire issued in the Dark Ages (500 AD – 1500 AD) in Europe in which there
would be almost no scientific advances.
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- In Asia, Persian Avicenna (1000 AD) proposed that fossils were caused by mysterious petrifying
fluids. He also proposed that a lot of rocks we see today were deposited by ancient oceans and that
mountains were formed by erosion of these ancient ocean sediments. He also classified minerals and
crystals.
- There are records of a few historic Eastern figures who had some geologic insight. Chu-Hsi
(Chinese, 1200 A.D.) correctly interpreted the origin of sedimentary rocks and fossils. He proposed
that sediments came from the erosion of mountains.
Middle Ages Geologic Concepts and Fossils
- The finding of fossils (remains of ancient life) in early times was almost always a source of mystery
to the masses and embarrassment to the “educated”.
- For most of Middle Age Europe (500-1500 AD), there were numerous interpretations to explain the
fossils that were found in the rocks:
-Works of the devil
-Early failed experiments of the Creator
-Victims of Noah’s flood
-Creatures that grew in the rock from “seeds” within the rocks
Continuing with the timescale
___1510 AD_____1553 AD________1650AD____1669 AD_____1725 AD________1800 AD__
Finding Fossils and Fake Fossils
- Take the case of Professor Beringer. - 1725, the arrogant Professor Beringer of Germany wrote
detailed papers explaining the occurrence of some really strange fossils that he had found. These
“fossils” were actually manufactured by his colleagues and were specifically carved out to test his
“knowledge” of fossils.
- Fake fossils are still a problem today, especially fossils from Morocco.
- It is not illegal to sell fake fossils.
Leonardo de Vinci and Geologic Concepts
- Earth’s “new” scientific beginning had its roots with the “Renaissance” that started in the 1500’s.
- Leonardo de Vinci (1510) made several correct interpretations of fossils.
-He recognized that fossil assemblages resembled living marine communities.
-He proposed that fossils were remains of once-living creatures.
-He noted interbedded fossiliferous and unfossiliferous layers of rocks, and inferred it was
unlikely that all of these fossils were formed by one worldwide flood.
Georgius Agricola (1553) is Considered To Be the Father of Mining and Mineralogy”
- Agricola's geological writings reflect an immense amount of study and first-hand observation, not
just of rocks and minerals, but of every aspect of mining technology and practice of that time.
Entering a Period of Increasing Geologic Knowledge
- Geologic knowledge began increasing dramatically from 1650 to the 1800s because:
1. More people became world travelers and observers
2. Mining of minerals for the industrial age would became a science; here knowledge of geological
factors is critical
3. People began collecting minerals and especially fossils as a serious hobby
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- The correct interpretations of fossils did not become widely accepted by many scientists until the late
1700s.
Modern Geologic Concepts: An Introduction to Sediments and Sedimentary Rocks
Stratified Sediments
- But what exactly were the earlier “Earth scientists” really looking at besides igneous rocks,
meteorites, etc. – they were looking at soil (sediment) and “layers” of (sedimentary) rocks. These
sediments would sometimes contain fossils.
- Sediments are deposited with floods, landslides, lake and ocean bottoms, wind-blown material, etc.
(thus we can relate sediments and sedimentary rocks to past environments)
Some Stratified Sediment Terms
- Stratum – refers to a single layer of sediment or rock
- Strata – two or more layers of sediments or rocks
- Bedding plane – contact between two beds or stratum
Drawing of Strata
bedding planes at arrows
Stratified Rock
- Sediments can lithify (be changed) into stratified rock
- “Special” sediments such as ejecta (rocks thrown into the air from volcanoes) such as volcanic ash,
pumice, and scoria, will settle back down to Earth and can also form layers of “sedimentary rock”.
- Stratified rocks are the most common type of rocks found on the Earth’s surface.
- Stratigraphy: simple definition - the study of strata (layers of sediments or rocks)
Stratified Rock Recording Environmental Changes
- Strata can be used to interpret the record of environmental changes on the Earth’s surface.
- For example, strata can be used to determine the paleo-climates (ancient climates) and the paleoenvironments (ancient environment) in which the sediments were originally deposited.
- The only strata that usually contain fossils are that of sedimentary rocks AND volcanic ash.
Let’s determine that we could have been as smart as some of the earliest geologists. We will
We will try to discover some geologic principles ourselves.
Rock Symbols
- Using the Lithologic Rock Symbol Chart (separate handout), memorize the symbols for limestone,
sandstone, shale, granite, metamorphic, unconformity and baked zone.
CLASSROOM EXERCISE – Developing Geologic Principles (6 pages)
There is no security on this earth, there is only opportunity. General Douglas MacArthur
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__1669 AD_______1750 AD__1760 AD__1775 AD__1778 AD__1790AD__1800 AD__
Some Stratigraphic Principles (Steno)
- This strata will finally be studied in great detain by Nicolas Steno (1636 – 1686), who is considered
to be the father of stratigraphy. He understood that fossils were from previous life forms and that
tongue stones were really shark teeth. In 1669, he published the following geologic principles that
were derived from his studies of sediments: (Figure 17.2 page 419)
1. Principle of Superposition: If undisturbed, the oldest layer of rock (stratum) will be at the bottom
of the sequence and the youngest layer of rock (stratum) will be at the top of the sequence.
2. Principle of Original Horizontality: Because of gravity, sediments will be deposited in essentially
horizontal layers or strata.
3. Principle of Lateral Continuity: A layer of sediment will extend laterally in all directions, until
the bed thins out or terminates against the edge of a basin.
- Later Steno abandoned his geological studies and became a priest.
Other Contributions of the 1700s
- Almost a hundred years later (1750) –in Germany, Johann Lehmann recognized that certain groups of
rocks tended to be associated with each other, often over large distances. For example, a certain red
sandstone might lie atop a distinctive limestone and beneath a particular green shale, and these rocks
might also appear in another location a great distance away. Such rock formations could be regarded
as chapters in the history of the Earth.
- Giovanni Arduino (1760) in Italy independently noticed and recognized similar rock formations in
the Alps. Arduino and Lehmann both wanted to divide Earth’s history into four major time units.
- Abraham Werner (teaching from 1775) influenced many to accept the concept of “Neptunism” (all
rocks came from a universal ocean – good for a world-wide flood) as opposed to “Plutonism” (many
rocks were created by melting and fire). Werner insisted that basalt lava was deposited as sediment
from water even as his students insisted that they saw a volcano where lava came from molten rock!
- The word "geology" was first used by Jean-Andre Deluc in the year 1778
There are three types of people in this world: those who make things happen, those who watch
things happen and those who wonder what happened. We all have a choice. You can decide which
type of person you want to be. I have always chosen to be in the first group.
Mary Kay Ash
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Uniformitarianism
- James Hutton (1790) is considered as the Father of Modern Geology. The science of geology really
began with the writings of Hutton. He was the first to interpret rocks as products and records of past
events in the Earth’s history (igneous, sedimentary and metamorphic) and was a “Plutonism”
advocate. His major contribution was to popularize the term Uniformitarianism.
Uniformitarianism: The present is the key to the past; present day geologic processes are the same
processes that have operated over vast amounts of time.
- The rates of geologic changes and intensity of geologic changes do not have to be constant
throughout time.
- This does not rule out that sometimes the Earth suffers from major (geologic) catastrophic events.
- Hutton even suggested that many animals have evolved over time, fifty years before Darwin.
Catastrophism (Noah’s Flood)
- This increasing of geologic knowledge would have “bumps” along the way with some strange
doctrines such as this one.
- Doctrine of Catastrophism: The Earth was shaped by a series of giant disasters that involved forces of
tremendous violence, surpassing anything experience in nature. Noah’s Flood easily fit into this
theory.
- This doctrine pervaded most Western chronologies of Earth History prior to the 1800s.
Unconformities (Hutton and Steno)
- Before the 1600s, man’s concepts of geology had very little scientific data upon which to estimate the
age of any rock sequence.
- Why not look at rock layers to see if we can get some “time reference” data?
- Stratigraphy: the study of layers of rocks (simple definition)
- What about the vertical relationships among the horizontal or conformable layers of rocks?
- We can assume that the older rock layers are on the bottom and the younger rock layers are on the
top.
- A bedding plane between strata may represent a depositional or erosional break of anywhere from a
few years to hundreds of years or more (inconsequential in geologic time).
- Unconformity: a surface or bedding plane representing erosion of rocks or non-deposition of rocks or
both processes (Figure 17.7, page 423). With the unconformity, any overlying bed would NOT be
conformable in geologic time.
An unconformity (without regard to rock type)
- The understanding of unconformities is critical to the full understanding of geologic time and
geologic history.
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- There are three classifications of unconformities based on:
a) Rock types beneath the unconformity, and
b) The arrangement of the rock layers beneath the unconformity.
Disconformity (with regards to rock type)
A. Disconformity: Erosion creates a surface somewhat parallel to the existing sedimentary
beds. Thus new, overlying beds will be deposited parallel to those beds below the
unconformity – the strata is “discontinuous” in time(Figure 17.8, page 424)
Nonconformity (with regard to rock type)
B. Nonconformity: Erosion creates a surface that is cut into igneous or metamorphic rocks.
Then this erosional surface of igneous and metamorphic rocks is later covered by layers of
sediments and sedimentary rocks (Figure 17.10, page 426). The rocks are NOT the same
type above and below.
Angular unconformity (with regard to rock type)
C. Angular Unconformity: Erosion creates a surface that cuts across folded or tilted strata.
Then this erosional surface of tilted (sedimentary) rocks is later covered by other parallel
layers of sediments and sedimentary rocks. (Figure 17.9, page 425)
All of us do not have equal talent, but all of us should have as an equal opportunity to develop
our talents. JFK
Understanding the relationship between: First, Last, Older, Younger
- Think of a family of kids: The first born is the oldest; the last born is the youngest.
- Thus we have the same relationship for geology: first is oldest; last is youngest
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More Geologic Principles (Hutton)
Folded strata
4. Principle of Deformation: Folds and tilted beds indicate deformation that postdates (after)
deposition. (Figure 17.2b, page 419) of textbook). Example: the sandstone was deposited
first, followed by the shale: both were first deposited horizontally, later the strata was folded
(notice how all the beds remain parallel but not horizontal)
Faulted strata (cross-cutting fault)
5. Principle of Cross Cutting Relationships: A rock feature that cuts through a host rock is
younger than the host rock it cuts. (Figure 17.2, page 419) of textbook). Example: the
sandstone was first deposited horizontally, followed by horizontal limestone, later the rock
units were broken with a “fault”.
Inclusion of older granite in younger sandstone
6. Principle of Inclusions: Igneous or sedimentary rocks that contain inclusions of other rocks
must be younger than the rocks they include. (Figure 17.5, page 422). Example: the granite
was first intruded into some type of rock, erosion removed all the overlying rock; then
sandstone was last deposited over the granite with some granite gravel mixed into the later
sandstone.
Baked zone (and inclusions)
7. Principle of Baked Contacts: An intruding or flowing igneous rock often “bakes or alters” the
rock surrounding it. (Figure 17.5, page 422). Example: the sandstone is the oldest, the
granite (when it was molten) incorporated pieces of sandstone into the granite and the granite
also “baked” the sandstone (so the granite is youngest or last).
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- These “relative age-dating” principles of Steno and Hutton can work well within any particular area
where rocks are visible.
- Problem: How do we relative age-date rocks and geological events world-wide since the same event
is not happening everywhere on the Earth at the same time? This is where fossils will play a major
role.
_____________1796 AD___________1815 AD__________1830 AD_______
Fossils and Rocks
- Baron Georges Cuvier (1796) is considered the Father of Vertebrate Paleontology
- He independently and simultaneously, discovered the principle of fossil succession (see next
paragraph). While studying mainly early mammal fossils he concluded that:
- a) Each fossil was unique to a set (or age) of rocks
- b) Recognized that many fossils were of extinct organisms
- But he was also a leader of the Noah Flood bunch (Catastrophists) and concluded that:
- c) Each fossil species resulted from a special creation
- d) Each set of fossils were subsequently destroyed by a series of catastrophic events
Fossils and Relative Age Dating (Smith)
- William Smith [Strata Smith] (1815) reasoned that older fossils are found in the lower beds and that
fossils in the upper beds would be younger. He also made one of the first accurate geologic maps.
8. Principle of Fossil Succession: Fossil assemblages succeed one another through time in a
regular and predictable order because: (Figure 17.6, page 423)
a) Biota has become more complex through time.
b). Fossil assemblages fossil biota are recognizably different over time.
(Here identical fossils are found in the shale at widely separated
locations, thus the shales must be of the same age!)
c). The relative ages of fossil assemblages can be determined over time.
- Strata with the same fossil assemblages are the same relative age (this is common used
by geologists).
- Fossils are “relative time” indicators.
- Now maybe we can piece together a world-wide geologic history and geologic time scale.
First Geology Textbook
- Finally we must recognize Charles Lyell who in 1830 published the first geologic textbook:
Principles of Geology
- Lyell is also called the Father of Historical Geology
If you think education is expensive, try ignorance.
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