When using pyrite to understand Earth’s ocean and atmosphere: Think local, not global Shallow water at the edge of the Pacific Ocean reflects cloudy morning skies at Moeraki Boulders Beach, on the South Island of New Zealand. (Image: Shutterstock) February 26, 2021 SHARE 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. Fike 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.