Fossils & Dating

Objectives:

    1.    Define fossil.

    2.    Describe how different kinds of fossils form.

    3.    Describe the principle of relative dating.

    4.    Explain the process of radioactive decay.

    5.    Define half-life.

    6.    Describe how radioactive dating is used to measure absolute time.

 

Notes:

The study of Earth's living past is contained in the Fossil record.  A fossil is simply any evidence of life preserved in rock.  Fossils come in many different forms as "Original remains" are often hard to come by.  Among the different types are:

 

 

 

 

 

(www.mccsc.edu/.../images/ fossil%20leaf.jpg)

 

Relative Time

Relative dating is the process of placing items and occurrences in order based on the times in which they occurred.  Relative dating does not determine the age of an item or event but rather gives an estimation of time based on geological clues.  Geological clues include the following:

(perth.uwlax.edu/.../ law_of_superposition_b.jpg)

Sometimes the geological record may be incomplete due to extreme geological forces such as uplift, subduction, and major plate movements.  These gaps are known as unconformities.  Unconformities explain why strata are sometimes at different angles (angular unconformity), missing (disconformity), or changed due to errosion (nonconformity).