List three types of evidence for seafloor spreading

Molten material found in the bottom of seafloors indicated underwater eruptions that formed new areas of the seafloor was presented as evidence for seafloor spreading. Due to earths magnetic polarity and its tendency to switch, iron present on the sea floor contained a magnetic record of sea floor expansion progress. Finally, drilling samples obtained in the seafloor indicated the deeper samples of were significantly older than the shallower samples that were brought up.