As new seafloor is created in a rift valley, old sea floor is melted back into magma. which process accounts for this melting

Are the layers of rock above and below the coal older or younger?

What is a group of organisms called

Some steps in cell division are shown below: 1. chromosomes condense and pair up 2. segments of dna of sister chromatids twist and cross 3. exchange of dna occurs between chromosomes 4. four daughter cells are created that are haploid which of the following steps is least likely to occur during meiosis 1?