E-Mail The ocean floor is vast and varied, making up more than 70% of the Earth's surface. Scientists have long used information from sediments at the bottom of the ocean -- layers of rock and microbial muck -- to reconstruct the conditions in oceans of the past. These reconstructions are important for understanding how and when oxygen became available in Earth's atmosphere and ultimately increased to the levels that support life as we know it today. Yet reconstructions that rely on signals from sedimentary rocks but ignore the impact of local sedimentary processes do so at their own peril, according to geoscientists including David Fike in Arts & Sciences at Washington University in St. Louis.