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 Magnetic Mapping of the Ocean Floor

Magnetic Mapping of the Ocean Floor
Reading Level
     edHelper's suggested reading level:   high interest, readability grades 5 to 7
     Flesch-Kincaid grade level:   5.87

Vocabulary
     challenging words:    oceanic, reversal, provides, magnetism, negative, reading, compass, wherever, record, surprising, settle, frontier, calculate, term, present, ocean

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Magnetic Mapping of the Ocean Floor
By Patti Hutchison 		  
1     The ocean has been called the last frontier. Conditions under the ocean surface have made it difficult to study. Not long ago, scientists felt that the ocean floor was flat. They thought oceanic crust was older than land. They thought it had not changed much over the years. Through the wonders of technology, we have recently been able to map the ocean floor.
 
2     A magnetometer is a device scientists can now use to study the ocean floor. This tool can detect small changes in magnetic fields. Ships tow these devices through the water. They record the strength of the magnetic field in rocks on the ocean floor. Scientists can use this data to make magnetic maps of the ocean floor.
 
3     Rocks containing iron give us a record of Earth's magnetic field. Basalt is one of these rocks. It is found in lava. As lava cools, the minerals settle parallel to the earth's magnetic field. They are like compass needles.
 
4     When the lava hardens, the magnetic course of these minerals is locked in place. It provides a record of the earth's magnetic field at the time of the eruption. Scientists have studied this record and noticed some patterns.
 
5     These patterns show periods of magnetic reversal over time. A magnetic reversal is a change in earth's magnetic field.

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