Grades:

Grade 11-12

Subjects:

Geography

Overview

In this lesson, students gain an understanding of the geologic time scale, use some standard techniques to determine age, and investigate how fossils are used to compile earth's geologic history.

Suggested Time Allowance:

1 hour

Objectives:

It is expected that students will:

• distinguish between relative and absolute time
• apply principles of relative age dating to the interpretation of geologic sequences
• correlate rock units from one area to another
• outline the process of absolute dating by means of radioactive elements
• use the principles of radiometric dating to solve simple problems related to absolute time
• determine age by direct observation, such as counting growth rings and varves
• explain the process of fossil formation
• describe how fossils are the key to the interpretation of past events
• use the geologic time scale to compare the ages and lengths of various segments of geologic time
• describe the earth's geologic history in terms of the development of life

Materials:

• Computers with Internet access
• Student Journals
  

Lesson Plan

Introduce students to Paleontology , the study of the developing history of life on earth, of ancient plants and animals based on the fossil record, evidence of their existence preserved in rocks. Explain how the earth's history dates back more than 4.5 billion years (Ga) which is divided roughly into 2 eons called the "cryptozoic" [Gr. kryptos, hidden + zoo, life] and the "Phanerozoic" [Gr. phanerous, visible + zoo, life]. [Paleoclimatologists usually use geological time divisions, which would be the Priscoan, Archean, Proterozoic, and Phanerozoic Eons.] The division of these two eons is the boundary of the Precambrian and the Cambrian which occurred about 570Ma (570Ma means 570 million years before present, ie 570,000,000 BP). Paleontologists employ a wide variety of skills to arrive at their theories and conclusions like the study of glaciers, sedimentary rocks and fossils.

• Provide a class demonstration of radioactive decay using a Geiger counter, and discuss the decrease of the parent isotope over time.
• Have students use simple ratios of parent atoms to stable (daughter) atoms to simulate the calculation of the absolute age of a rock (e.g., using plastic bags containing different ratios of colored beads representing parent/daughter atoms). Ask students to compare their ratio to a sample decay curve to determine the age of their sample.
• Have students count tree rings or the growth lines of a mollusc to find age by direct measurement. Have them deduce how this could be done with rocks.
• Set up fossil specimens at stations and have students, in groups: 1) brainstorm and record their answers on how the fossils may have formed (groups share their lists); 2) model various methods of fossilization (e.g., moulds, casts).

To explore the concept of geologic time, have students make a scale timeline on adding-machine tape (1 mm equals 1 million years) and organize events of biologic and geologic importance (e.g., origin of the earth and solar system, last glaciations, age of dinosaurs, first humans, Ancient Greeks).

Collect the students' geologic timelines showing significant events in history. Check the accuracy of the positions and information of geologic eras, periods, and epochs.

Ask them to write an essay on Paleontology for assessment.

Assessment:

Students will be evaluated based on their involvement in class discussions and subsequent essay.

Source:

NationMaster