Geologic Time

Pre-Concept Map Activity Using a sheet of copy paper, sketch a concept map of “Earth’s History” No one else thinks exactly the same as you, so no two maps should be the same Put the most general topics at the top and get more specific as you flow downwards Link ideas together with lines Write a few words or a phrase on the line that explains why the two ideas are linked together

Snickers Lab 1. What is the oldest layer of the Snickers? How do you know? 2. What is the youngest layer of the Snickers? How do you know? 3. Which is older, the peanuts or the caramel? How do you know? 4. With your lab group, decide on the steps to making a snickers bar.

THE RULES OF THE DATING GAME GEOLOGIC HISTORY THE RULES OF THE DATING GAME © Copyright 2005 - 2006  M. J. Krech. All rights reserved.

Time What is time?

Time is… Either relative or absolute Time is: a measured period during which an event, process, or condition exists or continues.

One Year = the time it takes the Earth to complete one orbit around the Sun.

Geologic Time Based on the same time units Generally much greater periods of time 100,000 years 1,000,000 years

Dating Techniques One ways in which geologists look at time: Relative Dating

Relative Dating is.. …the measure of a sequence of events without knowing the exact date at which the events occurred. What happened first? What happened next?

Principles of Relative Dating Principle of Superposition Principle of Cross-Cutting Principle of Inclusions Principle of Unconformities

Principle of Superposition The youngest rocks are on the top. The oldest rocks are on the bottom.

Principle of Superposition Q#1 Which rocks are older? Which rocks are younger?

Principle of Cross-Cutting Any feature that cuts across another rock or structure is younger than what it cuts across. You can't cut something until that something exists, therefore the cut has to be younger. Volcanic vents cutting across sedimentary rock layers - Which is youngest?

Principle of Cross-Cutting Q#2 What is younger? The rocks or the fault line?

Principle of Inclusions Rock layers which contain other rocks are younger than the inclusion. The inclusion (the other rocks)  is older!

Principle of Inclusions Q#3 Which is older? The rock layer or the rocks included in the layer?

Principle of Unconformities Unconformities are surfaces that represent gaps in the geologic record.

Principle of Unconformities missing rock layer = missing time

Rock Symbols

Where's the missing sediment? Q#4 How do you know?

Where's the missing sediment? Q#5 Where's the missing sediment? How do you know?

What happened first? Q#6 How do you know?

Where is the youngest rock? Q#7 How do you know?

Where is the unconformity? Q#8 How do you know?

What rock layer is the oldest? Q#9 How do you know?

Which is younger? The fault or the rock layers? Q#10 How do you know?

Does this diagram show an unconformity? Q#11 How do you know?

Which is younger? The rock layer or the inclusion? Q#12 How do you know?

The End BONUS: What do you see here?

“Understanding a Million” Activity How long would it take to count to a million? Well, counting once per second (easy at the start, but tough when you reach the hundred thousand mark), eight hours per day, seven days per week (no weekends off), it would take you a little over a month to count to one million!

“Understanding a Million” Activity One possible way to actually see a million individual objects is to use a computer and print out a million asterisks. Using a word processor on a computer, type out one page filled with nothing but asterisks. Print the page and count the number of asterisks there are on the page. Divide this number into one million to see how many pages it will take to print one million asterisks. Print out the right number of pages and put them all up on one wall. Then you will be able to see one million objects all at once! Once you have seen a million asterisks, calculate how many classroom walls, like the one you used, it will take to put up one billion asterisks (Don't actually do it. It will take too much paper!) Or just for fun, see how many candles you can put on a birthday cake and then try and figure out how large a birthday cake you would need to celebrate Mother Earth's birthday!

Chart Observations “first humans appeared on Dec 31st, 9:24 PM and one second before midnight ‘Voyage of Christopher Columbus’ - Year 1492″. Now: The first second of New Year’s Day - Widespread development of science and technology; emergence of global culture; acquisition of the means of self-destruction of the human species; first steps in spacecraft planetary exploration and the search of extraterrestrial intelligenc.

Geologic Time Activity Compare geologic time to the length of a football field, which is 100 yards long. Earth formed about 4.6 billion years ago. That's 4,600,000,000! If you divided 4.6 billion by 100, then each yard equals 46,000,000 years, and each ten yard section equals 460,000,000 years.

Geologic Time Activity Making a Time Line Print out or draw a model of a football field. (Note: The "print out" option provides you with a scale model of a 25-yard section of a football field and two end zones. You will need 4 copies of the 25-yard section but only 1 copy of the end zones.) Starting at the left (4.6 billion years ago) and "moving forward in time," label the 10-yard lines in years. Then, using different colored markers, draw a horizontal line to show the beginning and end of each of the following periods and eras. Cenozoic Era (65 million years ago [mya] to present) Triassic (245-208 mya), Jurassic (208-146 mya), and Cretaceous (146-65 mya) periods Paleozoic Era (570-245 mya) Proterozoic Era (2500-570 mya) Archaean Era (3800-2500 mya) Hadean Era (4600-3800 mya) Option: Make a circle, pie diagram, or clock that shows the amount of time in degrees (there are 360 degrees in a circle) or in percentages for the following: a clock of the 4.6 billion year history a clock of the Mesozoic (Triassic, Jurassic, and Cretaceous) a clock of the Mesozoic to the present.

Geologic Time Activity Finding an Event in Time Many important events have occurred since Earth formed 4,600 million years ago (mya). Below is a list of some of those events. Your task is to mark on a time line when those events took place. If you haven't already done so, you might want to begin with the "Geologic Time Activity." That activity provides a scale model of a football field that can be used for this activity. Mark the spot on the time line with an "X" where the following important events in Earth's history occurred. first microscopic life (3.6 bya) first multicellular life (900 mya) first oxygen appears in atmosphere (1.9 bya) first land plants appear (450 mya) formation of the Himalayas begins (30 mya) formation of the Atlantic Ocean begins (150 mya)

Geologic Time Activity In the example below, we have used the football-field model for our time line. On it we have marked the first appearance of dinosaurs (225 mya), the disappearance of dinosaurs (65 mya), and the first appearance of homo sapiens (1/2 mya).

Geologic Time Activity Option: As a group activity, it might be fun to create a geologic time line on the floor of your classroom or a hallway. First, you will need to measure the length of the place you have chosen to make your time line. Second, determine how many inches, feet, or yards represent a given number of years by dividing 4.6 billion by the length of your "time line." To mark the events in Earth's history, you might prepare a sign representing each event and have students hold the signs and stand in the proper time spots on your geologic time line. (4.6 billion years is a big number to represent. To prevent the need for "student-markers" to stand on top of one another, you may want to use a very large space, such as a gym or a sidewalk for your time line.)