Chapter 1: Plate Tectonics Challenge Reading
Directions: Read the passage once without annotating. Then, while reading it a second time, annotate using the
following symbols. Feel free to write comments or notes in the margins as you read.
= unfamiliar vocabulary terms
?
= key words or details to the meaning of the passage
= I don’t understand
Is the Earth Preparing to Flip?
Something unexplained is happening to Earth’s magnetic field. In recent years, the field has been
behaving in ways not previously seen in the admittedly short time it has been monitored. Some researchers think it
may presage a geomagnetic reversal when the North and South magnetic poles flip.
Earth’s magnetic field is caused by motions in the ball of molten iron that lies at the center of our planet.
Electrical currents in the outer part of the core result in the planet-wide magnetic field. The magnetic field not only
shields us from harmful cosmic rays but also funnels charged particles shed by the Sun towards the magnetic
poles.
The field is also an invaluable aid to navigation. Even though today we have the pinpoint accuracy of the
satellite-based Global Positioning System, many still rely on their compass needling pointing to magnetic north.
But as all who use a compass know, the position of the magnetic pole changes and there is evidence that it is
changing at an increasing rate.
Working for the Canadian Government-funded Geolab, it is Larry Newitt’s job to track the wandering north
magnetic pole. Every few years he undertakes an expedition to measure the position of the pole. Today the pole is
at sea and the expedition can only be done at the end of the winter when the sea is frozen.
Placing magnetic sensors on the ice, the expedition attempts to surround the magnetic pole and
triangulate its correct position. But each time they go back it’s moved. “It is now moving northward, away from
Canada to Siberia, at a rate some four times faster than it used to,” said Dr. Newitt.
The reason for the wandering of the magnetic pole is twofold. One cause is from beneath our feet, the
other from above our heads. Short-term jitter is caused by the influence of the solar wind on Earth’s magnetic field
high in the atmosphere. But the steady drift reflects what is going on in Earth’s core.
But something else is happening to Earth’s magnetic field; it is getting weaker. David Kerridge, of the
British Geological Survey, says “There is strong evidence that the field is decreasing by about 5% per century.”
Some researchers suggest that it could be the start of a geomagnetic reversal, when the strength of Earth’s
magnetic field decreases and then returns a few thousand years later with the north and south magnetic poles
reversed.
Looking back in the geological record, it is clear that, on average, such events occur about every 250,000
years. However, it has been about 750,000 years since the last reversal-so we are certainly overdue.
By Dr. David Whitehouse, BBC News
p. 125
Chapter 1: Plate Tectonics Challenge Reading
Directions: After reading and annotating the passage, answer the questions below.
1. Write the words and definitions for at least 3 unknown vocabulary terms you circled in the passage in the
space below. If you believe you know all the vocabulary from the passage, write the 3 terms and definitions
you are LEAST familiar with.
2. What causes Earth’s magnetic field?
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3. What does the magnetic field do?
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4. How does Larry Newitt track the north magnetic pole?
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5. How is the location of the north magnetic pole changing?
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6. What is the reason for the moving magnetic pole?
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p. 124