Lecture outline - Introduction to physical
geology.
Physical geology = study of the
processes that shape the surface and interior of the earth.
Physical geology as a discipline
is evolving into earth system science. What does that
mean?
The basic goal of this course is
then to gain some initial understanding of how the earth operates.
Why
would one want to do that?
Course mechanics:
Philosophy of science:
Since physical geology is a scientific
endeavor it makes sense to consider the basic nature of that endeavor.
Some highlights in the history
of geologic thought:
Natural theology and cosmogenies, early hypotheses.
A basic driving question of the time - how does nature reflect
the design of the creator?
Thomas Burnet, 1691,
Sacred Theory of the Earth
- forces involved not extant these days.
- earth's history of short duration.
- global catastrophic events (especially floods).
- where did the water come from? An interesting
and valid scientific question at the time.
James Hutton,
uniformitarianism and the rock cycle in the late 1700s:
- inventor of rock
cycle, past and present not disjunct.
- "Thus in understanding the proper
constitution of the present earth, we are led to know the source
from whence had come all the materials which nature had employed
in the construction of the world which appears: a world contrived
in consummate wisdom for the growth and habitation of a great
diversity of plants and animals; and a world peculiarly adapted
to the purposes of man, who inhabits all its climates, who measures
if extent, and determines its productions at his pleasure."
...... " no vestige of a beginning, no prospect of an
end"
- uniformitarianism,
observe todays natural systems operating and look for unique
signature. Presence of that signature in the rock record indicates
a similar natural system operated in the past.
- "no vestige of a beginning, no prospect
of an end." The earth as perfect machine.
William
Smith's 1815-17 map:
Charles Lyell
and deep geologic time in the Victorian era:
- important works 1820-1850, Principles
of Geology widely read.
- deep geologic time, construction of histories
from detailed geologic field studies, including mapping and measurement
of stratigraphic columns.
Alfred Wegener,
continental drift and scientific progress in the 1920s. We will
return to in some detail later.
Plate tectonic revolution of the 1960's:
- seafloor spreading
hypothesis of Vine and Mathews.
- core definition of plate tectonics: The
earth's outer shell is broken up into relatively-rigid curved
plates that move large lateral distances with respect to each
other. This activity determines much of the spatial distribution
of different types of geologic activity and their evolution through
time.
- Plate boundary types: divergent, convergent,
and transcurrent and mixed. Each has its unique character.
Useful themes in geology
we will return to throughout the course.
- How can we understand complex systems?
- Behavior of open and complex natural systems
- the use of cycle concepts and flow diagrams. The hydrologic
cycle as one example.
- Chaos - what is it?
- Fuzzy logic:
how to deal with imperfect or incomplete knowledge?
- Immensity of deep time.
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