Final answer:
The Earth's history of magnetic pole reversals is recorded in the patterns of magnetic minerals found in ocean floor rocks, which align with the Earth's magnetic field when they solidify, revealing a timeline of reversals on the Geomagnetic Polarity Time Scale.
Step-by-step explanation:
We know that the magnetic poles have reversed over Earth's history through the analysis of rock on the ocean floor, particularly through the study of the magnetic minerals in igneous rocks that make up the oceanic crust. As magma comes to the surface and cools to form new rock, the iron-rich minerals within align with the Earth's magnetic field. This creates a record of the direction of the magnetic poles at the time the rock solidified. Thus, the correct answer is a. It shows up in the rock on the ocean floor.
Scientists can analyze these patterns of magnetic orientation in rocks to identify magnetic reversals, which are evident in the symmetric stripes of alternating magnetic polarity found on either side of mid-ocean ridges. These findings contribute to the Geomagnetic Polarity Time Scale (GPTS), mapping the history of magnetic field reversals.
The proof of magnetic pole reversals over Earth's history is evident in the magnetic mineral patterns found in ocean floor rocks. As new ocean floor forms, magnetic minerals within igneous rocks align with Earth's magnetic field, creating a pattern that, upon cooling, records the magnetic orientation at that time. These patterns, which become magnetic stripes symmetrically arranged about mid-ocean ridges, reveal a historical record of Earth's magnetic field reversals. Such studies have provided a detailed timeline, the Geomagnetic Polarity Time Scale, showing that the direction of Earth's magnetic field has changed or reversed approximately every 200,000 years. This provides plagiarism free content for an understanding of geophysical processes that have taken place over Earth's long history.