1. Daily Warm-Up Exercises
Day 26
What are the three major types of rock?
igneous, metamorphic, and sedimentary
What's the main difference between the three rock types?
The main difference is in how they form
What do many of a rock's features depend on?
Where and how the rock was formed.
Daily Warm-Up Exercises 1
Daily Warm-Up Exercises 1

2. Contrasting Case Activity 4 Earth History, Investigation 6
Compare Time Scales
Contrasting Case Activity 4
Earth History, Investigation 6
In this activity, students will compare two different kinds of diagrams that depict Earth’s history. The numeric scales (table and timeline) will help students begin to get used to starting with the present and moving backward into the past. The proportional scales (football field & clock) will help them begin to understand that the world we live in gradually emerged over a very long period of time, and that humans have only existed for a fraction of that time.
Materials needed:
•time scales (worksheets 15-18)
•comparison tables (worksheets 19 & 20)
Compare Time Scales
Compare Time Scales

3. Age of Earth Earth’s history is measured in millions of years.
How much is a million?
1,000 times 1,000
1,000 thousand
Earth was formed about 4,500 million years ago.
How much is 4,500 million?
4,500 times 1,000 times 1,000
The purpose of this slide is to help students begin to comprehend the very large numbers involved in geologic time scales.
If time permits, try some of the “Describe a Million” activities listed on page 225 of the FOSS manual.
4,500 thousand thousand
4,500,000 thousand
Compare Time Scales
Compare Time Scales

4. Human Life Humans first appeared about 200,000 years ago.
How much is 200,000?
200 times 1,000
200 thousand
How does our age compare with Earth’s?
4,500,000 thousand
200 thousand =
4,500,000
200
This slide will help students begin to understand how old Earth is and how young the human race is by comparison. When you reduce the fraction comparing our age to Earth’s, you see that, for every year humans have existed, Earth has existed for over twenty thousand years.
Tell students that the FOSS materials will say Homo sapiens appeared 40,000 years ago, which was what scientists used to believe. More recent fossil discoveries have led scientists to believe we actually appeared somewhat earlier.
Additional note: All the other numbers in both numeric time scales match the numbers used in the FOSS materials. Geologists have since adjusted many of the period dates. You can find current information at =
45,000 2 =
22,500 years
1 year
Compare Time Scales 4
Compare Time Scales 4

5. Numeric Scale 1 - Table Compare Time Scales
Distribute the two numeric scales (worksheets 15 & 16). As you do this, reassure students that they will not be required to memorize all the information in these diagrams. Tell them that the four time scales they will examine today illustrate different ways of showing the same information. As they work with the scales, encourage them to think about how displaying information in different ways can help us see different things.
Ask students to look at the table and explain the note at the top of the Dates column. The note says MYA stands for million years ago. Help your students understand that all the numbers in this table show how many millions of years ago something happened.
Next, use questions to help your students see that this table is like layers of sediment: the oldest layer is on the bottom and the most recent is on top. If we read through this table from top to bottom, we would start with the present and move backward into the past. If we wanted to follow the course of Earth's history from its formation to the present, we would need to start at the bottom and work our way up.
Compare Time Scales
Compare Time Scales

6. Complete Column 1 Table Timeline Paleozoic Era 4,500 mya 570 mya
Which part looks like it lasted longest?
When did precambrian time begin?
When did precambrian time end?
How long did precambrian time last?
When did the paleozoic era begin?
When did paleozoic era end?
How long did paleozoic era last?
When did modern humans appear?
Paleozoic Era
4,500 mya
570 mya
3930 million years
570 mya
245 mya
Distribute the numeric comparison table (worksheet 19) and have students work in pairs to complete the first column. Answers will appear one-by-one on keypress. [The questions on the slide are shortened. See the student worksheet for the complete questions.]
Before displaying the timeline, tell students that, in the next scale, history "flows" in a different direction. Encourage them to ask themselves, "If I want to follow Earth's history from past to present, how do I need to read this scale?" In the table, the past is at the bottom and the present is at the top. How will the next scale show history?
325 million years
200,000 years ago
Compare Time Scales 6
Compare Time Scales 6

7. Numeric Scale 2 - Timeline
4,500
million years ago
(mya)
Quaternary – Modern humans appear 200,000 years ago
Tertiary – Dinosaurs become extinct
Cretaceous – Rocky Mountains are formed
Jurassic – Flowering plants appear
Triassic – First dinosaurs
Permian – Great Extinction
Pennsylvanian – First reptiles
Mississippian – First amphibians
Devonian – First insects
Silurian – First land animals
Ordovician – First land plants
Cambrian – First trilobites
Earth is formed; water appears on Earth’s surface; earliest, bacteria-like life appears
Cenozoic
Today
1.6
mya 66
144
208
245
286
320
360
408
438
505
570
Mesozoic
Paleozoic
Precambrian
Time
Students should easily see that, in the timeline, history "flows" from left to right.
Compare Time Scales
Compare Time Scales

8. Complete Column 2 Table Timeline Paleozoic Era Paleozoic Era 4,500 mya
Which part looks like it lasted longest?
When did precambrian time begin?
When did precambrian time end?
How long did precambrian time last?
When did the paleozoic era begin?
When did paleozoic era end?
How long did paleozoic era last?
When did modern humans appear?
Paleozoic Era
Paleozoic Era
4,500 mya
4,500 mya
570 mya
570 mya
3930 million years
3930 million years
570 mya
570 mya
245 mya
245 mya
Why are these called numeric scales? Students will probably recognize that “numeric” has to do with numbers. Both NUMERIC SCALES (table and the timeline) use numbers to show how many millions of years ago different things happened.
325 million years
325 million years
200,000 years ago
200,000 years ago
Compare Time Scales 8
Compare Time Scales 8

9. Proportional Scale 1 - Football Field
Today
(100 yards)
START ZONE
END ZONE
Earth is formed
(0 yards)
Cenozoic Era (98.5 to 100 yds)
Mesozoic Era (95 to 98.5 yds)
modern humans appear (99.99 yds)
Rocky Mountains form (97 yds)
flowering plants appear (96.5 yds)
first dinosaurs (94.5 yds)
first reptiles (93 yds)
first amphibians (92 yds)
first insects (91 yds)
first land plants (90 yds)
first land animals (90.5 yds)
first trilobites (88 yds)
earliest, bacteria-like
life appears
(22 yds)
water appears on
Earth’s surface
(11 yds)
Great Extinction (94 yds)
dinosaurs become extinct (98.5 yds) 10 20 30 40 50 60 70 80 90
Precambrian Time (0 to 87 yds)
Paleozoic
Era
(87 to 95)
Distribute the two proportional scales. Encourage your students to examine the football field and again ask themselves, "If I want to follow Earth's history from past to present, how do I need to read this scale?" Students should easily see that the football field is like the timeline, with the past on the left and the present on the right.
Compare Time Scales
Compare Time Scales

10. Complete Column 1 Football Field Clock precambrian time 0 yards
Which part looks like it lasted longest?
When did precambrian time begin?
When did precambrian time end?
How long did precambrian time last?
When did the paleozoic era begin?
When did paleozoic era end?
How long did paleozoic era last?
When did modern humans appear?
precambrian time
0 yards
87 yards
87 of 100 yards
87 yards
95 yards
Distribute the proportional comparison table (worksheet 20) and have students work in pairs to complete the first column. Answers will appear one-by-one on keypress. [The questions on the slide are shortened. See the student worksheets for the complete questions.]
8 of 100 yards
99.99 yards
Compare Time Scales 10
Compare Time Scales 10

11. Proportional Scale 2 - Clock
dinosaurs become extinct (11:39 pm)
Earth is formed (midnight)
Rocky Mountains are formed (11:14 pm)
Today (midnight)
START
END
flowering plants appear (11:12 pm)
first dinosaurs (10:42 pm)
modern humans appear
(seconds before
midnight) 12
Great Extinction (10:33 pm) 12
first reptiles (10:24 pm) 11 1 11 1
Ceno-
zoic
Era
first amphibians (10:04 pm)
Mesozoic
Era
first insects (9:52 pm)
first land animals
(9:46 pm)
(10:42 -
11:39 pm) 10 2 10 2
first land plants
(9:39 pm)
water appears on
Earth’s surface
(2:40 am)
Paleozoic Era
(9: :42 pm)
first trilobites
(9:05 pm)
9 am
3 am
9 pm
3 pm
Precambrian Time
(12:00 am - 9:00 pm)
Precambrian Time
(12:00 am - 9:00 pm) 8
You will probably need to help your students understand this diagram. Tell them the two clocks represent one day, to show what Earth’s history would look like if it all happened within 24 hours. The left clock shows the first 12 hours, from midnight to noon, and the right clock shows the second, from noon to the following midnight. To make sure they understand this, you might have them think about their own 24-hour day, beginning last night at midnight. For example, point to midnight on the left clock and say, "Think about what you were doing last night at midnight." Point to 3 am and say, "Think about what you were doing at 3 o'clock this morning." Ask, "What time did you wake up this morning?" and point to the times students mention. This type of discussion will help students connect the clock representation to a day in their own lives.
When you think your students have made that connection, go back and look at what the clocks show about Earth's history. Precambrian Time lasted from midnight last night, when most of us were sleeping, until 9 o'clock tonight, when most of us will be winding down at the end of our day. If Earth was formed last night at midnight, we wouldn't be here yet. All the plants and animals we're familiar with won't even start to appear until after 9 pm, and modern humans won't appear until seconds before midnight tonight. 4 8 4
earliest, bacteria-like
life appears
(5:20 am) 7 5 7 5
6 am
6 pm
Morning
Afternoon
Compare Time Scales
Compare Time Scales

12. Complete Column 2 Football Field Clock precambrian time
Which part looks like it lasted longest?
When did precambrian time begin?
When did precambrian time end?
How long did precambrian time last?
When did the paleozoic era begin?
When did paleozoic era end?
How long did paleozoic era last?
When did modern humans appear?
precambrian time
precambrian time
0 yards
midnight
87 yards
9:00 pm
87 of 100 yards
21 of 24 hours
87 yards
9:00 pm
95 yards
10:42 pm
Answers will appear one-by-one on keypress.
These are called PROPORTIONAL TIME SCALES because they show how different parts of Earth's history compare to the whole. Both the clock and the football field show that precambrian time makes up a huge proportion of Earth’s history. In comparison, the cenozoic era’s proportion is small, and human history’s is really, really tiny.
8 of 100 yards
less than 2 hours
99.99 yards
after 11:59 pm
Compare Time Scales 12
Compare Time Scales 12

13. Compare Categories
What can you learn about Earth’s history from the numeric scales but not from the proportional scales?
That Earth was formed 4,500 million years ago.
That it took thousands of millions of years for plants and animals to appear.
Numeric scales are more precise than proportional scales.
Compare Time Scales
Compare Time Scales

14. Compare Categories
What can you learn from the proportional scales but not from the numeric scales?
It’s obvious that precambrian time is longer than all three eras put together
You can easily see how young the human race is compared to Earth.
You can see how far along in Earth’s history different things happened.
Proportional scales make it easy to see how things compare. With the numeric scales, you can subtract and compare numbers, but it’s difficult to see how everything fits together.
Compare Time Scales 14
Compare Time Scales 14

15. Compare Categories
Could you include numeric information in the clock or football field?
Add the date to each event or time division.
Could you include proportional information in the table or timeline?
Make the size of each box show how long that section lasted.
In part 2, the class will work with a 45-meter timeline that includes both numeric and proportional information, with 1 cm representing 1 million years. In part 3, students will create miniature versions, with 1 mm equal to 1 million years. Although their timelines will be too small to include a lot of numbers, you might encourage them to incorporate at least some numeric information.
Compare Time Scales
Compare Time Scales