 |
 |
|
 |
 |
BASIC GEOLOGY
AND
GROUNDWATER
The study of ancient rocks indicates that the earth
is 4.6 billion years old. An easy to understand
example to illustrate the unfolding of the earth over
its entire lifespan of 4.6 billion years is to think of
the entire 4.6 billion years as simply a single 24-
hour day.
This example allows us to more easily see how the
timing of certain events in the earth’s history relates
to other events. So let us say that the entire age, 4.6
billion years of the earth’s age is simply a 24-hour
day, from midnight to noon (the A.M. period) and
from noon to midnight (the P.M. period).
The first complex life forms, trilobites, appeared at
about 530 million years ago or 9.14 P.M. Note that
over 80% of the earth’s history had already occurred
by the time these life forms had appeared. At 9.24
P.M. the first fish appeared. Reptiles arrived at
10.27 P.M., or 300 million years ago. Dinosaurs
roamed the planet from 230 million years ago until
65 million years ago or until 11.40 P.M.
The first birds appear at 11.14 P.M., or 150 million
years ago. And then just a minute before midnight,
at 11.59 P.M., humankind makes its appearance on
earth, or less than two million years ago.
During this entire time, 4.6 billions years, geologic
processes have been continually shaping the world.
|
 |
|