UEN Security Office
Technical Services Support Center (TSSC)
Eccles Broadcast Center
101 Wasatch Drive
Salt Lake City, UT 84112
(801) 585-6105 (fax)
Students will use their knowledge about fossils to arrange fossil pictures in sequence from oldest to youngest.
Scientists have good evidence that Earth is very old, approximately four and one-half billion years old. Scientific measurements such as radiometric dating use the natural radioactivity of certain elements found in rocks to help determine their age. Scientists also use direct evidence from observations of the rock layers themselves to find the relative age of rock layers. Specific rock formations are indicative of a particular type of environment existing when the rock was being formed. For example, most limestone represents marine environments, whereas, sandstones with ripple marks might indicate a shoreline habitat or riverbed.
The study and comparison of exposed rock layers or strata in different areas of Earth led scientists in the early 19th century to propose that the rock layers could be correlated from place to place. Locally, physical characteristics of rocks can be compared and correlated. On a larger scale, even between continents, fossil evidence can help in matching rock layers. The Law of Superposition, which states that in an undisturbed horizontal sequence of rocks the oldest rock layers will be on the bottom, with successively younger rocks on top of these, helps geologists correlate rock layers around the world. This also means that fossils found in the lowest levels in a sequence of layered rocks represent the oldest record of life there. By matching partial sequences, the truly oldest layers with fossils can be worked out.
By correlating fossils from various parts of the world, scientists are able to give relative ages to particular strata. This is called relative dating. Relative dating tells scientists if a rock layer is older or younger than another. This would also mean that fossils found in the deepest layer of rocks in an area would represent the oldest forms of life in that particular rock formation. In reading Earth history, these layers would be read from bottom to top or oldest to most recent. If certain fossils are typically found only in a certain rock unit and are found in many places worldwide, they may be useful as index or guide fossils in finding the age of undated strata. By using this information from rock formations in various parts of the world and correlating the studies, scientists have been able to construct the geologic time scale: This relative time scale divides the vast amount of Earth history into various sections based on geological events (sea encroachments, mountain-building, and depositional events), and notable biological events (appearance, relative abundance, or extinction of certain life forms).
1. Use Science Process and Thinking Skills
4. Communicate Effectively Using Science Language and Reasoning
Invitation to Learn?
Teaching about Earths history is a challenge for all teachers. The idea of millions and billions of years is difficult for children and adults to comprehend. However, relative dating or time can be an easy concept for students to learn.
In this activity, students begin a sequencing activity with familiar itemsletters written on cards. Once they are able to manipulate the cards into the correct sequence, they are asked to do a similar sequencing activity using fossil pictures printed on rock layer cards. Sequencing the rock layers will show students how paleontologists use fossils to give relative dates to rock strata.
Questions to ask:
Schmoker, M. 1999. The key to continuous school improvement. Results 2nd Edition Association for Supervision and Curriculum Development pg. 71
We labor under the incorrect notion that students must master basic skills before they can learn higher-order skills or engage in complex activities. Studies in math, reading, and writing clearly demonstrate that the opposite is true. Students learn best when basic skills are taught in a vital challenging context that makes the skills meaningful. The very thing that keeps students from achieving in these areas is the dry irrelevant teaching strategies we often employ, especially with students who most need real challenges. (Means, Chelemer, and Knapp, Teaching Advanced Skills to at Risk Students: Jossey-Bass 1991)
Schmoker, M. 1999 The key to continuous school improvement Results 2nd Edition ASCD pg. 73
Virtually every teacher has acquired some semblance of training in this highly effective method (cooperative learning), estimates are that only about 10 percent of teachers use cooperative learning. One of the simplest forms of cooperative learninghaving students occasionally work in pairs to ensure each others understanding of difficult concepts can be expected to bring immediate effects especially among low-achievers. They also found that such simple pairings are especially effective in helping students to succeed in math and science. (Joyce B. Weil and Showers 1992 Models of Teaching. New York: Allyn and Bacon.)