Essentials of Geology (Geol 1030)
Laboratory #10-Time, Earth History, & the Fossil Record
Introduction
Geology is divided based on the succession of life within the fossil record.
Because this record was amassed by different workers in separate locations within the
world, the geologic time scale has been assembled piecemeal. The names applied to
these divisions are derived from locations where the rocks were mapped, the type of
fossils in those rocks, or by the type of rocks that dominate that portion of the record.
The largest divisions of the time scale are the eons, which are the Hadean,
Archean, Proterozoic, and Phanerozoic (in chronological succession from oldest to the
most recent). The Hadean eon is one for which we have no rock record and is thought to
have been a molten tumultuous time for our planet. We often lump this eon with the
Archean and Proterozoic eons, due to the sparse data that is available for this part of the
Earth’s History. Collectively, these eons are called the Precambrian and cover the time
from 4,600,000,000 to 545,000,000 years ago. The remainder of earth history falls
within the Phanerozoic, which is subdivided into the Paleozoic, Mesozoic, and Cenozoic
eras. The Earth’s history is more finely divided into periods, epochs, and ages. For
example, the “Great Ice Ages” occurred during the Pleistocene epoch of the Quaternary
period during the Cenozoic era of the Phanerozoic eon.
There is not a single location where the entire time scale is represented by rocks
we can see. This exercise is designed to help you graphically understand the enormity
geologic time scale and help us to grasp the concept of deep time.
You will need one of the following two sets of materials, depending on the weather:
Rainy Days Clear Days
Adding machine tape Pavement or Asphalt
Masking tape Colored Sidewalk Chalk
Pencil or pen Meter Stick
Colored markers or pencils Ruler
Meter stick Geologic Time Scale on page 20 of your
text
Ruler
Geologic Time Scale
