Determine If the Following Statements Are True Or False

Name: ______Date: ______Hour : _____ Earth as a Magnet Worksheet True or False Determine if the following statements are true or false. _____ 1. The north end of a compass needle always points to 90° north latitude. _____ 2. Earth’s magnetic field extends outward from the planet in all directions. _____ 3. Earth’s magnetic poles have switched places many times over the past hundred years. _____ 4. Once molten rocks harden, their magnetic domains are frozen in place forever. _____ 5. Earth’s outer core is made up mainly of iron and nickel. _____ 6. Charged particles move inside Earth when it spins on its axis. _____ 7. Harmful particles from the sun are repelled by Earth’s magnetic poles. _____ 8. Magnetic reversals were discovered by William Gilbert in 1600. _____ 9. Earth’s south magnetic pole is the same as Earth’s south geographic pole. _____ 10. Migrating birds may detect Earth’s magnetic field with structures in their eyes.

Critical Reading Read this passage from the text and answer the questions that follow. Magnetic Field Reversals Earth’s magnetic poles have switched places repeatedly over the past hundreds of millions of years, each time reversing Earth’s magnetic field. Scientists don’t know for certain why magnetic reversals occur, but there is hard evidence showing that they have occurred. The evidence comes from rocks on the ocean floor. At the center of ridges on the ocean floor, hot magma pushes up through the crust and hardens into rock. Once the magma hardens, the alignment of magnetic domains in the rock is frozen in place forever. The newly hardened rock is then gradually pushed away from the ridge in both directions as more magma erupts and newer rock forms. Rock samples from many places on the ocean floor reveal that magnetic domains of rocks from different time periods are aligned in opposite directions. The evidence shows that Earth’s magnetic field reversed hundreds of times over the past 330 million years. The last reversal was less than a million years ago.

Questions 1. What is a magnetic field reversal?

2. What evidence shows that magnetic field reversals have occurred? Multiple Choice Circle the letter of the correct choice.

1. Like a bar magnet, planet Earth a. exerts magnetic force. b. has a magnetic field. c. has magnetic poles. d. all of the above

2. Earth’s true north magnetic pole is actually located near Earth’s a. equator. b. south magnetic pole. c. south geographic pole. d. none of the above

3. Earth’s magnetic field extends outward from Earth for a. a few kilometers. b. about 100 kilometers. c. about 330 kilometers. d. several thousand kilometers.

4. The magnetosphere a. completely surrounds Earth. b. is found only near Earth’s poles. c. exists over a region larger than Earth. d. two of the above

5. Which statement about magnetic reversals is false? a. Magnetic reversals have occurred hundreds of times. b. The most recent magnetic reversal occurred 330 million years ago. c. There is hard evidence showing that magnetic reversals have occurred. d. Scientists do not know for certain why magnetic reversals have occurred.

6. The idea that Earth is a magnet was first proposed a. by William Gilbert in 1800. b. after seismographs were developed. c. before scientists learned about Earth’s inner structure. d. around the same time that Earth’s outer core was discovered.

7. Many migrating birds a. navigate using Earth’s magnetic field. b. may be able to see Earth’s magnetic field. c. have natural “compasses” that they use for migration. d. all of the above Matching Match each definition with the correct term. Definitions _____ 1. about 80° north latitude

_____ 2. solid sphere that makes up Earth’s center

_____ 3. exactly 90° north latitude

_____ 4. region deep inside Earth that consists of liquid metals

_____ 5. Earth’s magnetic field

_____ 6. switching of Earth’s north and south magnetic poles

_____ 7. navigation device that always points north

Fill in the Blank Fill in the blank with the appropriate term. 1. A compass needle always points to Earth’s north ______pole.

2. What we call Earth’s north magnetic pole is actually the ______pole of magnet Earth.

3. Earth’s magnetic field is strongest at the ______.

4. The alignment of magnetic domains in rocks on the ocean floor provides evidence for magnetic ______.

5. Earth is a magnet because of the movement of charged particles in Earth’s ______.

6. Earth’s magnetic field protects living things from harmful particles given off by the ______.

7. A(n) ______is a device that detects and measures earthquake waves. Critical Writing Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences. Describe Earth’s magnetic field, and explain how it benefits living things.

______