Intro geol

An introduction to Earth Science

•The nature of Scientific Ideas
•What is Geology?
•A brief history of Geology
•The state of Catastrophism
in the 20th century


The nature of scientific ideas
Science is a system of knowledge that is based on
general “truths” or facts as they are known at the time.
Scientists use observations (to gather the facts) and
deduction to offer explanations of natural phenomena.
Deductive reasoning: to draw conclusions regarding a
phenomenum based on all that is known about it.
Earth Science (Geology) focuses on natural
phenomena that are related to the Earth.


How do we develop and express such explanations
of natural phenomena?
• Speculation: simply opinion or guess.
• Hypothesis: a logically derived explanation that is based
on a body of knowledge that is made up of “facts”;
everything known about what is being explained.

•It remains tentative (possibly wrong) until
further evidence and rigorous testing proves it
better than other hypotheses; are new “facts” that
become known consistent with the explanation?

Ockham’s Razor (Principle of Parsimony):
Given more than one hypothesis for a given phenomenon
the simplest hypothesis is always preferred!
(the simplest has fewer assumptions and unknowns)
• Theory: a very well verified and communicated
explanation that links together a number of separate
hypotheses.

Theories provide a basis for predicting outcomes
and these outcomes can be tested by further
observation.
Extensively documented theories that explain many
aspects of the natural world are called paradigms.


• Law: Theories become Laws (e.g., the Law of
Gravity) when they are shown to be absolutely
correct for the conditions to which they apply.
“The history of knowledge has been characterized by
periodic formulation of hypotheses that generalized the
most factual information available at a given time…

Science is a process of continuous refinement and
testing of such generalizations…
Hypotheses inevitably have been colored by the
temperaments, experiences and prejudices of
their advocates…”
Robert Dott

In a more brutally honest quote:

“There are no facts, only interpretations.”
Nietzsche


What are the implications to scientific progress?

“The greatest obstacle to progress in science is the illusion of
knowledge….the illusion that we know what’s going on but
we don’t.”
Professor Mike Disney, Cosmologist, Cardiff University


What is geology?
Geology: a science that deals with the history of the earth
and its life especially as recorded in rocks.
The science that deals with:

•The materials that make up the Earth (rocks and
minerals).

•Processes acting within the Earth and at its surface.
•The history of the Earth.


Physical Geology: involved with the processes that act to
form the Earth and the products of those processes.

e.g., Minerals

Earthquakes

Rocks

Volcanoes

Plate tectonics



Historical Geology: involved with the interpretation of the
history of the Earth.


Based on the recognition of the signature of changing
environments over time, as preserved in the rock record.
Environmental interpretation of rocks
+
Age of rocks
= Earth History


Large scale cross-bedding in 240
million year old rocks in the
Central US.

= windblown sand dunes; the
Central US was a desert at that

time.


Environmental interpretation:
The present is the key to the past.
By examining the characteristics of various environments on Earth
today we can interpret the environments in which ancient sediments
were deposited.


Age of rocks:
Based on relative age (relative to associated rocks)
or
absolute age (radiometric dating).

Earth History:
The history of changing environments on Earth.


A Brief History of Geology
Herodotos (500 BC): recognized that the Nile River deposited
sediment during flood (i.e., the land surface was modified by
natural processes).
Aristotle (384-322 BC): recognized that fossils in rocks
resembled many living organisms; concluded that fossils were
once-living animals. Implies that rocks formed since there was
life on Earth.
Theophrastus (374-287 BC): wrote the first book on the
minerals that make up rocks.

A Brief History of Geology
St. Thomas Aquinas (1225-1274): explained all geological
phenomena in terms of the biblical account.
Landscape on Earth today was formed during creation or
modified during the biblical Flood.
Fossils in rocks in the mountains were washed there by the
Flood.
Leonardo da Vinci (1452-1519): deduced that
fossils represented past life and that they could not
have been transported by floods to mountainous
areas where they were found.


A Brief History of Geology
James Ussher (1581-1665):
Provided the first estimate of the age of the
Earth…based on the genealogies of the Bible.

Concluded that the Earth formed on October 23, 4004 BC.
…..at 9:00 in the morning.
The Earth was created and remains pretty much as it was on
Day 1 except for changes due to catastrophic events.



April 9, 1903 the Earth
changed for the people of
the town of Frank, Alberta.

3 km2 buried
in 100 seconds.
80 million tonnes;
30 million m3.


A Brief History of Geology
Modern Geology is Born (late 18th C)
Neptunism versus Plutonism
Neptunists: believed that
all rocks (including igneous
rocks) were formed by
deposition from an early
global ocean. The Oceans
receded and the Earth
surface has been much the
same ever since.

Plutonists: believed that rocks
formed by igneous processes
(i.e., all rocks formed by
crystallization from a magma).

Neither correct but sparked a healthy debate!


A Brief History of Geology
Abraham Werner (1749-1817): the founder of
modern geology and the champion of Neptunism.
Werner was the first to postulate a history of the

Earth, recognizing that the Earth underwent change
over time.
James Hutton (1726-1797): introduced the
Principle of Uniformitarianism.
That the Earth changes very slowly over time in
response to natural processes that we can see acting
today as they have always acted on Earth. E.g., river
valleys are cut slowly by the streams that occupy them.


A Brief History of Geology
Hutton believed that everything about the Earth must be
interpreted in terms of the processes that act in a slow,
ongoing manner over time.
Georges Cuvier (1769-1832)
The father of modern Catastrophism and first
to recognize that extinctions have taken place
over Earth history.
Suggested that the Earth has always been more-or-less the
same but it periodically undergoes “Revolutions”
(catastrophes); periods of rapid and extensive change.


A Brief History of Geology
Cuvier did not have an explanation for the “revolutions”, he
just recognized evidence that major events had taken place.
Charles Lyle (1779-1875):
Prolific author and follower of Hutton’s Principle.
These ideas appeared in the first edition of Principles of
Geology (1830) and in all of the 12 editions that followed.

Lyle’s writings shaped geology by the end of the 19th century.
The Principle of Uniformitarianism was entrenched making it
difficult for contrary ideas to be accepted by geologists.


Canadian Profile
Sir William Logan
(1798-1875)
Ranked the top Canadian
scientist in history.
First Canadian to be knighted.
Conducted extensive field work mapping the geology of
Canada.
First to recognize (and promote) the mineral wealth of
Canada.
Founded the Geological Survey of Canada.