Homework Help

Geological evidence of seafloor spreading (A)Shows that earth's magnetic field has...

user profile pic

farina | Student, College Freshman | (Level 2) eNoter

Posted June 5, 2013 at 6:31 PM via web

dislike 1 like

Geological evidence of seafloor spreading

(A)Shows that earth's magnetic field has always pointed north

(B) Shows a pattern of alternating normal and reversed polarity

(C) Shows that the magnetic pattern on one side of a mid-ocean ridge is a mirror of the other side of a mid-ocean ridge.

(D) A and B

(E) B and C

2 Answers | Add Yours

user profile pic

jely44 | College Teacher | (Level 1) Adjunct Educator

Posted June 15, 2013 at 4:48 AM (Answer #1)

dislike 0 like

The Earth's magnetic field has a history of varying and changing throughout most of the planet's life. The geological evidence for this, using sea floor spreading to confirm, is the very intentional and obvious turns in the top layer of the crust. Many minerals found in and on the Earth, when formed and in a solidified state, line up to the magnetic field. If a mineral cools now, the “North” direction it aligns to can be very different from one that forms later or that has formed in the past. In addition, sections of the ocean floor mirror each other. So E is the correct answer.

Sources:

user profile pic

ncchemist | eNotes Employee

Posted June 16, 2013 at 3:04 AM (Answer #2)

dislike 0 like

The correct answer here is E.  The Earth's magnetic poles have reversed several times over the course of geological time.  Depending on the orientation of the planet's magnetic field, the magnetic particles in the crust aligned in different orientations.  Also, the changes in alignment of the magnetic particles is a mirror image across an oceanic ridge where seafloor spreading occurs.  These facts combined helped to prove the notion of plate tectonics and the fact that new crust is formed along these ridges where the plates diverge.  This process is called seafloor spreading.

Sources:

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes