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Lecture

ERSC 1F90 Lecture Notes - Cross-Bedding, Theophrastus, Geosphere


Department
Earth Sciences
Course Code
ERSC 1F90
Professor
Dale Hess

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A VIEW OF EARTH
Earth is a planet that is small and self-contained
Hydrosphere
Atmosphere
Biosphere
Geosphere
EARTH AS A SYSTEM
Earth’s four spheres are linked as a system through their interactions
Vary on spatial scales from fractions of a millimeter to thousands of kilometers
Have time scales that range from milliseconds to billions of years
Characterized by processes that
Heat remaining from Earth’s formation, and heat that is continuously generated by
radioactive decay, power the internal processes that produce volcanoes, earthquakes, and
mountains
The Earth system is also powered by the Earth’s interior
WHAT IS THE ENVIRONMENT
Best defined as all that surrounds us with which we interact”
This can be pretty far-reaching (e.g. Mars rovers, Voyager, etc.)
For this course, although we will talk about the solar system, our “environmentwill be the planet earth
shown in the Apollo images
WHAT IS GEOLOGY
From the Greek geo (Earth) and logos (discourse)
The science that pursues an understanding of planet Earth
Geology is very multidisciplinary. It draws from physics, chemistry and biology - an Earth Systems
Science approach.
But wait a minute, what is science?
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 phenomena based on all that is known
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; 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?
OCKHAMS RAZOR :
Given more than one hypothesis for a given phenomenon
the simplest hypothesis is always preferred!
(the simplest has fewer assumptions and unknowns)
An Introduction To Your Planet
Earth Science Page 1

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(the simplest has fewer assumptions and unknowns)
Theory: a very well verified and communicated explanation that explains all of the data
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
Science is a process of continuous refinement and testing of such
generalizations…
THE SCIENCE OF GEOLOGY
Physical geology - examines the materials composing Earth and seeks to understand the
many processes that operate beneath and upon its surface
Historical geology - seeks an understanding of the origin of Earth and its development
through time
Geology is the science that pursues an understanding of planet Earth
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.
Earth Science Page 2
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