Education
Lessons and Activities: Understanding the Geologic Time Scale
Relative vs. Absolute Time
Introduction
By knowing the age of the rock that a fossil is found in, geologists can
usually tell the age of the fossil. Sometimes they cannot give it an exact
date, but they know that it is older or younger than another fossil. Dating a
fossil by saying it is older or younger than another fossil is called relative
dating.
If the geologists know the exact age of a fossil, they usually express
its age in millions of years ago (mya) that it was formed. Dating a fossil by
assigning it a specific age is called absolute dating.
Instructions
To practice this concept, make a relative time scale out of seven or eight
events that have occurred in your lifetime. For example, include important
events such as your birth, something you did today, starting kindergarten, and
losing your first tooth.
Remember, these events only show chronological order,
not exact dates. After making a relative time scale, assign dates to the
events that you chose, so that it is an absolute time scale. The following is
an example.
Example Time Scale
| I was born. |
|
I was born. |
July 25, 1984 |
| I took my first steps. |
|
I took my first steps. |
April 2, 1985 |
| My little sister was born. |
|
My little sister was born. |
June 23, 1987 |
| My family and I went to Disneyland. |
|
My family and I went to Disneyland. |
May 21, 1995 |
| Today |
|
Today |
Today's date |
