Despite all the deep-sea expeditions and samples taken from the seabed over the past 100 years, humans still know very little about the ocean’s deepest reaches. And there are good reasons to learn more. Most tsunamis start with earthquakes under or near the ocean floor. The seafloor provides habitat for fish, corals and complex communities of microbes, crustaceans, and other organisms. Its topography controls currents that distribute heat, helping to regulate Earth’s climate. July 30 marks the 100th anniversary of the birth of Marie Tharp, a geologist and oceanographer who…