In the Cretaceous period of earth history there is clear evidence that the climate was much warmer than today. It was so warm that areas near the pole had tropical vegetation like palm trees, and there was almost certainly no sea ice and glaciers probably only existed at very high altitude. This produced widespread anoxia (stagnant, no-oxygen condition) on the floor of the oceans. From your knowledge of ocean circulation, which of the following explanations could account for the anoxia?
◦ The lack of polar sea ice stopped any thermohaline deep circulation in the oceans, stratifying the water column to produce anoxia in the deep sea.
◦ The greenhouse affect made planktonic algae grow so fast that they filled the ocean with algae, stagnating the ocean.
◦ The greenhouse affect led to so much CO2 in the atmosphere that animals all died from lack of oxygen, stagnating the oceans.
◦ The water got so warm it couldn't hold any oxygen, stagnating the water column.
Cutaway Model of Earth
Climate Zones
Earth Science, 14/E
Embryonic Period
Embryonic Period
The origin and spread of modern H. sapiens, reconstructed from genetic and fossil evidence.