An expedition to the Mediterranean answered some long-standing questions about the ocean's history. A. The Glomar Challenger expedition investigated changes in invertebrate fauna and some unusual geologic features. B. Researchers collected fossils to determine which new species migrated from the Atlantic with older species. C. Scientists aboard the Glomar Challenger were the first to discover the existence of domelike masses underneath the seafloor. D. Samples recovered from the expedition revealed important differences in chemical composition and fossil distribution among the sediment layers. E. Evidence collected by the Glomar Challenger supports geologists' beliefs that the Mediterranean had evaporated and become a desert, before it refilled with water. F. Mediterranean salt domes formed after crustal movements opened the straits between the Mediterranean and the Atlantic, and the Mediterranean refilled with water.