Teaching about absolute dating
The students should begin by using the scale factor to determine the correct placement of each organism on the time scale model.The students will find the scaled distance by dividing the absolute age of the organism by the corresponding scale factor (See attachments for teacher key.) Next, the students should find the organism to most recently exist and measure the scaled distance from the end of the paper marked "Today". [Using a scale factor of 1 millimeter=1 million years-100,000/1,000,000=0.1 mm] The students will measure 0.1 mm from the end of the paper marked "Today" and place the Absolute Age card for "First Modern Humans" at this location. The students will continue these steps for the remaining organisms until the oldest organism is placed on the timeline. [Using a scale factor of 1 meter=1 billion years-2,500,000,000/1,000,000,000=2.5 m] The students will measure 2.5 m from the end of the paper marked "Today" and place the Absolute Age card for "Bacteria" at this location.For example, about 1.5 percent of a quantity of Uranium 238 will decay to lead every 100 million years.
Many chemical elements in rock exist in a number of slightly different forms, known as isotopes.
Since this lesson serves an introduction to geologic time scales, including relative and absolute age, students do not need to have an understanding of these concepts before beginning the lesson.
This lesson will require students to work in collaborative groups to create a scaled model timeline.
Students who finish the independent activities can complete a review activity using the following website: "Geologic Time" from the University of California Museum of Paleontology at Berkeley.
Students who need additional preparation before the lesson or extra review after the lesson can complete the activities on the following website: "Geologic Time" from the University of California Museum of Paleontology at Berkeley.
to answer reflection questions about the concepts learned while creating the scaled geologic timeline using the Geologic Time Scale Model Reflection Questions handout.