Physical Geology lecture outline
- Rock cycle, a closed or open system.
The traditional conception of the rock cycle.
- textbook depictions.
- origin in Hutton's world view.
Two important metaphors - Time's
cycle and Times Arrow.
Discussed by Stephen J. Gould, 1987, Time's
Arrow Time's Cycle, Harvard University Press.
- "Judeo-Christian traditions have
struggled to understand time by juggling and balancing two ends
of a primary dichotomy about the nature of history. In our traditions,
these poles have received our necessary attention because each
captures an unavoidable theme in the logic and psychology of
how we understand history -- the twin requirements of uniqueness
to mark moments of time as distinctive, and lawfulness to establish
a basis for intelligibility.
- At one end of the dichotomy - I shall
call it time's arrow - history is an irreversible sequence of
unrepeatable events. Each moment occupies its own distinct position
in a temporal series, and all moments, considered in proper sequence,
tell a story of linked events in a direction.
- At the other end - I shall call it time's
cycle - events have not meaning as distinct episodes with casual
impact upon a contingent history. Fundamental states are immanent
in time, always present and never changing. Apparent motions
are parts of repeating cycles, and differences of the past will
be realities of the future. Time has no direction."
Is the standard depiction of the rock
cycle that of a cycle or an arrow, and is it an open or closed
Significance of the metaphors.
What can be added to create a more powerful
depiction of the rock cycle/system?
Above is my depiction of an open rock cycle.
Reservoirs are depicted as yellow boxes, and the processes by
which material transfers from one reservoir to another are given
in purple. Believe it or not this diagram involves substantial
simplification. Trace some paths through it to understand the
connections better. What does such a diagram suggest about the
nature of the earth's geologic history?
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