What Happened Before

Exploring Fossils with

Mike Baldwin

5th Grade Science TEKS

(5.11). The student knows that certain past events affect present and future events. The student is expected to

(A) Identify and observe actions that require time for changes to be measurable, including growth, erosion, dissolving, weathering, and flow;

(B) Draw conclusions about "what happened before" using data such as from tree-growth rings and sedimentary rock sequences

What is a fossil?

Something left by a plant or animal that lived long ago!

What must happen for a fossil to form?

For a fossil to form, something must get buried!

To start with an animal or plant must die in a location where it will not decay too rapidly (In water or where it will be buried quickly).

Fossilization

SedimentationAs time passes sediments bury the organism. The faster this happens the more likely fossilization will occur. Land and mud slides definitely help.

As the sediments continue to pile on, the lower layers become compacted by the weight of the layers on top. Over time, this pressure turns the sediments into rock.

Erosion at workRain, wind, earthquakes, freeze and thaw all work toward erosion. The mountains that were built up are worn away over time. Our fossil once again sees the light of day!

Index Fossil

Index fossils are fossils used to identify geologic time periods. Index fossils are important because, although different rocks may look different depending on the conditions under which they were laid down, they may include the remains of the same kinds of fossils.

Trace Fossil

• Trace fossils are structures preserved in sedimentary rocks that record biological activity. Strictly defined, trace fossils must reflect both the anatomy of their maker in some way, and be the result of behavior

Dinosaur tracks are an example of trace fossils

Explain how the trace fossil of the dinosaur foot could be formed.

1.

2. Sedimentation:

3. Rock formation:

4. Erosion:

Erosion exposes rock layers so that fossils can be discovered.

Rock layers can move!

Sometimes a fault can change the location of a rock layer.

Answer the questions on your worksheet about the stratigraphic

column below.

Vocabulary

Fossil

Strata

Stratigraphic column

Trace fossil

Index fossil

Sedimentary rock

Erosion

The End

Mike Baldwin