Clues to Earth’s Past
WWW.GLENCOE.COM Integrated Science
Level Blue 2005 code DCF26EA8B0
Paleontologist-scientist who studies
fossils
Per mineralized remains- fossils in which
the spaces inside are filled with minerals
from groundwater
Carbon film- thin film of carbon residue
preserved as a fossil
Cast- type of fossil that forms when
crystals fill a mold or sediments wash into
a mold and harden into rock
Index fossils- remains of species that
existed on Earth for a relatively short
period of time, were abundant, and were
widespread geographically
Emerge- to come out into the open; to
appear.
Why index fossils are more useful to
paleontologists than many other fossils:
They are useful because the species they
represent only lived for a short period of
time. This means that any rock containing
that fossil formed during that short period
of time. Scientists can use them to
estimate the age of the rock layers.
Information about
environment revealed by
fossils
If area was
land or
covered by
water.
In areas that
were covered
by water,
depth of the
water
Past climate of
the area
Principle of superposition
Relative age
Unconformity
Sequence- one thing following another in a
fixed order
When you know the relative age of a rock
layer, you know only how old it is compared
with other things, such as other rock
layers. When you know the actual age of a
layer of rock, you know approximately how
many years old the rock layer is.
Model how a folded rock formation would
form:
Drawing should show horizontal rock layers
Drawing should show the same layers folded.
Angular Unconformity:
1. Layers of sedimentary rock are tilted and uplifted.
2. Exposed rock layers erode.
3. Sedimentary layers are deposited on top.
Disconformity:
1. Sedimentary rock is exposed.
2. Some rock layers erode.
3. Sedimentary layers are deposited on top.
Nonconformity:
1. Igneous or metamorphic rocks are uplifted.
2. Exposed rock erodes.
3. Sedimentary layers are deposited on top.
Match up rock layers
Following the layer
across an area
Using fossil evidence that
shows the same types of fossils
in both places