Name______Class______Date______
Skills Worksheet
Math Skills
Scientific Notation and the Rate of Plate Movement
Sometimes scientists who study the geologic history of Earth must work with very large numbers. For example, Pangaea began breaking up 250 million, or 250,000,000, years ago. Scientific notation is a way of expressing large numbers such as this without writing the place-holding zeros. A number writ-ten in scientific notation is expressed as the product of two factors: a number between 1 and 10 and a power of ten. For example, the scientific notation for the number 250,000,000 is 2.5 108.
When you write a number in scientific notation, you first need to identify the digits that are not place holding zeros. Place the decimal point after (to the right of) the leftmost digit. Then find the exponent for the factor of 10 by counting the number of places that you moved the decimal point.
SAMPLE PROBLEM
In 300 million years, a tectonic plate that moves 4 centimeters per year will move 1,200,000,000 centimeters. Express this distance in scientific notation
SOLUTION
Step 1: Identify the number without the place-holding zeros.
12
Step 2: Place the decimal point after the leftmost digit.
1.2
Step 3: Find the exponent by counting the number of places that you moved the decimal point in the number.
1,200,000,000 1.2
You moved the decimal point nine places to the left. Therefore, the exponent of 10 is 9.
Step 4: Write the number in scientific notation.
1.2 109
Math Skills continued
PRACTICE
Using the sample problem as a guide, answer the following questions. Remember to show your work.
1.Fill in this chart showing years in the supercontinent cycle.
Years / Number withoutPlace-holding 0s / Power of 10 / Scientific notation
Pangaea forms: 300,000,000 years ago
Pangaea splits in two: 160,000,000 years ago
Continents moving to their current positions: 60,000,000 years ago
2.The Nazca plate off the west coast of South America moves an average of 16 cm per year. In 50 million years, it will move 800,000,000 cm. Express this number in scientific notation.
3.Use the formula rate = distance time to work the following problem: The Pacific plate on which the city of Los Angeles is located is moving northwest as the plate on which San Francisco is located is moving southeast. The two cities are moving closer to one another at a rate of about 0.00005 km per year. The cities are now a distance of about 611 km apart. How many years from now will the cities meet? Express the answer in scientific notation.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Earth Science1Plate Tectonics
ANSWER KEY
to oceans and other continents, and its mountain ranges
22.When continents move, air flow and moisture change, causing climates to change.
23.ice
24.South Pole
25.Continents began to drift around the globe.
26.They may be separated and unique species may evolve from existing species.
27.the fossa
28.Madagascar separated from Africa about 165 million years ago and separated from India about 88 million years ago. This isolated the plants and animals on the island of Madagascar, leading to unique species evolving.
29.D
30.A
31.D
32.B
33.A
34.D
35.B
36.C
37.D
38.D
39.C
40.Gondwanaland broke into the two continents, one of which became South America and Africa.
41.A rift between South America and Africa opened about 150 million years ago.
42.The other continent of Gondwanaland separated to form them.
43.As India broke away from Australia and Antarctica, it moved north and collided with Eurasia.
44.about 60 million years ago
45.Collisions of the drifting continents welded new crust onto the continents and uplifted the land.
46.New oceans opened up and others closed.
47.Africa will collide with Eurasia. The Mediterranean Sea will close.
48.It will separate from the rest of Africa and move eastward, resulting in the formation of a new ocean.
49.The North American and South American plates will move westward and the Eurasian and African plates will move eastward.
50.It will move north and collide with Eurasia.
51.It will move to where Alaska is today.
52.They will come together to form a new supercontinent.
Math Skills
1.300,000,000: 3, 8, 3 108
160,000,000: 1.6, 8, 1.6 108
60,000,000: 6, 7, 6 107
2.800,000,000 cm = 8 10 to the 8th
power =8 108
3.0.00005 = 611 km time in years
0.00005 time = 611 km
time = 611 km 0.0005 km/yr =
12,220,000 = yrs.
1.222 107
Graphing Skills
1.oxygen and silicon; 74.3%
2.magnesium; 2.1%
3.Only small amounts of these elements are necessary to enrich a substance, because even the small amounts present in the continental crust are considered enriching.
4.Average Chemical Composition of Basaltic Layer of Oceanic Crust
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Earth Science1Plate Tectonics