Oceans by Simon Holland5/9/2023 ![]() ![]() The shallow oceans followed suit, but the deep oceans were anoxic, at least during the intense Neoproterozoic ice ages. ![]() Stage 4 (0.85–0.54 Ga) saw a rise in atmospheric oxygen to values not much less than 0.2 atm. Most of the surface oceans were mildly oxygenated, as were the deep oceans. Atmospheric oxygen levels did not change significantly. ![]() Stage 3 (1.85–0.85 Ga) was apparently rather ‘boring’. The shallow oceans became mildly oxygenated, while the deep oceans continued anoxic. During stage 1 (3.85–2.45 Gyr ago (Ga)) the atmosphere was largely or entirely anoxic, as were the oceans, with the possible exception of oxygen oases in the shallow oceans.ĭuring stage 2 (2.45–1.85 Ga) atmospheric oxygen levels rose to values estimated to have been between 0.02 and 0.04 atm. The last 3.85 Gyr of Earth history have been divided into five stages. ![]()
0 Comments
Leave a Reply. |