What signals the end of one cycle and the beginning of another?

Explain how the political influence of african americans leaders became weaker.

When new rock is added to an oceanic ridge, the magnetized strips on either side of the ridge are evidence of sea-floor spreading. this is because the rocks on the two sides of the ridge o are equal in width and in polarity are polar opposites oare magnetized vary in width but are equal in polarity

What’s the student’s scientific question