Understanding Geologic Time
Objective
NC 5.01 Interpret ways in which rocks, fossils and ice cores record Earth's geologic history and the evolution of life including geologic time scale, index fossils, Law of Superposition, unconformity, evidence for climate change, extinction of species and catastrophic events
NC 5.02 Correlate evolutionary theories and processes including biological, geological and technological
NC 5.03 Examine evidence that the geologic evolution has had significant global impact including distribution of living things, major geological events and mechanical and chemical weathering
Materials
Computer with internet access
Scavenger Hunt or Focus Questions worksheet
p.berkeley.edu/education/explorations/tours/geotime/gtiframe.html
Procedure
1. Explain to students how you will be navigating through the module. If you have enough computers, you may want to have the students work in small groups to complete the activity.
2. Pass out either the Focus Questions or Scavenger Hunt worksheet to the students. Give the students time to explore the module thoroughly.
Focus Questions
Directions: Answer the following questions as you navigate through Understanding Geologic Time.
1. How is relative age different from the actual date of an event?
2. What can radiometric dating tell us about the age of rocks that the Law of Superposition cannot?
3. How can you find the age of a layer of rock that is surrounded by layers of volcanic ash?
4. What do the periods in the geologic time scale represent?
5. What do the terms Paleozoic, Mesozoic and Cenozoic mean?
Focus Questions Answer Key
Directions: Answer the following questions as you navigate through Understanding Geologic Time.
1. How is relative age different from the actual date of an event?
Relative age only tells us the order in which events occurred, from the earliest to the most recent. Knowing the actual date of an event allows us to say exactly how old something is or how long ago it actually took place.
2. What can radiometric dating tell us about the age of rocks that the Law of Superposition cannot?
Radiometric dating tells us how old the rocks are whereas the Law of Superposition can only be used to determine the relative age
3. How can you find the age of a layer of rock that is surrounded by layers of volcanic ash?
Once you have found a radiometric age for the surrounding layers of volcanic ash, you can safely state that the age of the intervening layer is intermediate between those dates.
4. What do the periods in the geologic time scale represent?
Each period represents a change in the plants and animals at that time
5. What do the terms Paleozoic, Mesozoic and Cenozoic mean?
Paleozoic means ancient life, Mesozoic means middle life and Cenozoic refers to the time of recent life.
Scavenger Hunt
As you navigate through Understanding Geologic Time, keep your eyes open for answers to the following questions.
1. Find the book. Find any page in the book and describe what is happening there.
2. Find the word superposition. What does it mean?
3. Find the woman scientist. What is she studying? What will she learn?
4. Find the Jura Mountains. What country are they in and what period was named for them?
5. What do the periods on the geologic time scale represent?
BONUS QUESTION: What is a eurypterid?
SUPER BONUS: When did ammonites become extinct?
Scavenger Hunt Answer Key
As you navigate through Understanding Geologic Time, keep your eyes open for answers to the following questions.
1. Find the book. Find any page in the book and describe what is happening there.
Answers will vary.
2. Find the word superposition. What does it mean?
Superposition refers to the fact that in a series of undisturbed rock layers the older layers will be on the bottom and the younger layers will be near the top.
3. Find the woman scientist. What is she studying? What will she learn?
The scientist is studying the chemical composition of the rocks to establish their numeric age.
4. Find the Jura Mountains. What country are they in and what period was named for them?
The Jura Mountains are located in Switzerland. The Jurassic Period, which spanned the period between 196-130 million years ago is named after them.
5. What do the periods on the geologic time scale represent?
Each period represents a change in the plants and animals of that time.
BONUS QUESTION: What is a eurypterid?
Eurypterids were one of the fiercest predators in ancient seas. Some reached more than two meters (six feet) in length, making them the largest arthropods that ever lived. The last ones went extinct about 245 million years ago.
SUPER BONUS: When did ammonites become extinct?
Ammonites were a type of chambered mollusk (similar to the living Nautilus) that went extinct at the same time as the dinosaurs, about sixty-five million years ago.