You have made magnetic field measurements near some lavas at 60N, 90W. The incli

Question

You have made magnetic field measurements near some lavas at 60N, 90W. The inclination of the lava’s magnetization is 24 degrees.

a)Suppose the lavas were not tilted after cooling below the Curie temperature. In what circumstance would the orientation of the lava’s magnetization NOT represent the orientation of the paleomagnetic field at the time of the lava’s cooling? Is this circumstance likely to be the case?

b) Calculate the paleolatitude at which the lavas cooled.

c) A previous flow, which from field evidence can be argued to have cooled slowly, shows reverse magnetization. From other information, you believe it to have been formed 5 degrees closer to the equator. What do you expect the inclination to be?

Explanation / Answer

a) The circumstance in which lava's magnetization would not represent the orientation of the paleomagnetic field at the time of lava's cooling is if there is any other external magnetic field (due to electric current, etc) acting in the region near the lava flow. This is a highly unlikely situation as there were no other sources of an external magnetic field in the past and even if there were then the field must be strong enough to affect the huge volume of lava flows.

b) We use the formula tan I = 2 tan

Given Inclination= 24 degrees.

tan(24)= 2 tan

0.4452 = 2 tan

tan = 0.2226

= 12.55º

The paleolatitude at which the lavas cooled is 12.55º.

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