The ocean covers more than 70% of Earth's surface, yet around 80% of the ocean remains unexplored. To put it simply, we know very little about most of the ocean. A vital part of exploring the seafloor is mapping the density of the ocean crust(洋壳). Sea floor maps increase the scope, efficiency, and pace of deep-sea exploration, keeping scientists and boats from "flying blind. "
But it requires a significant wave source. The most common method for determining crustal structure is also controversial — firing seismic air guns(地震气枪)from ships. While this method is effective, it is potentially harmful to marine life and not easy to use. Now scientists are using animal vocalizations, the echoes of fin whale songs in particular, to learn more about the deep sea.
Fin whales are the second largest species of whales on the planet, second only to the blue whale. Found in the offshore waters of every major ocean, these endangered animals can reach a lifespan of about 90 years. The song of the fin whale is one of the loudest in the animal kingdom, and is detectable over great distances. It is so powerful that it can go through volcanic rock and sediment(沉淀物)on the ocean floor. Ocean-bottom seismometers off the coast of Oregon picked up on the seismic waves of these fin whale calls. Researchers Kuna and John Nabelek, from Oregon State University, analyzed six whale songs. Using these signals, the team was able to map the thickness of sediment and rock on the ocean floor.
While fin whale songs are never going to replace seismic air guns entirely, they do provide a free and natural alternative for scientists looking to explore the ocean floor. "Our study demonstrates that animal vocalizations are useful not only for studying the animals themselves but also for investigating the environment that they inhabit. "
