Earth's Geologic Time Scale
"There is not enough time!
But we live and we die by time, don't we? Let us not commit the sin of turning our backs
on time."
---- "Chuck Noland" (Tom Hanks) to "Wilson" (the soccer
ball) in Cast Away
Most people have at least seen a
geologic time chart similar to the one below. Unfortunately, comprehending the vast
stretches of "deep time" represented by each period is nearly impossible.
And the chart as shown is not to scale -- the eons, eras, and periods into which they are
subdivided are not depicted according to their true relative length. There
is not enough room here!
Earth is approximately 4.6 billion years old, so everything below shown as
the Phanerozoic Eon, for example, is only about 12% of its history. Many of the
rocks seen around the Phoenix area were formed about two-thirds of the way through Earth's
history.
Most of the mountains seen around Phoenix were formed only within the last 1%
of its history, and the filling of the valley floors with the soil we see now began only a
blink of an eye ago.
Stretches of time important to the GeoHistory of the Phoenix area
and the Superstition Mountains are highlighted below in red -- the Quaternary
and Tertiary Periods, and the Precambrian Eon.
Stretches of time important to the GeoHistory of the Sedona area
are highlighted below in blue -- the Mesozoic Era.
|
