Responses

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Responses:

1) Mara Guluzian

Mass extinctions occur during a short amount of time and wipe out more than half of all species. There are 5 major extinctions that have occurred throughout Earth's history, each one unique. The cretaceous-tertiary extinction occurred 65 million years ago. It is the most recent one, wiping out roughly 50% of plants and animals. It is a major turning point in earth's history marking the end of geologic period called the Cretaceous and starting a period known as the Tertiary period. It is also known as the K-T extinction, it ranks third in severity compared to the other mass extinctions. The most known vertebrates that became extinct were the dinosaurs. It is interesting how the different organisms were affected by the mass extinction. For example, land plants were better off than land animals. Effects on amphibians and mammals was mild and many reptiles species survived. The most famous theory behind this extinction is a theory from Walter Alvarez and Luis Alvarez. The theory states that a meteorite or comet impact may have triggered the extinction from projecting rock debris into the atmosphere making the Earth dark for a period of time. 

 

Source: 

https://www.britannica.com/science/K-T-extinction 

2) Townsend Porcher

Ok, so I browsed some of the recent literature on the End-Triassic Extinction, or, as referred to in Table 14.2, the Triassic Event. There is no doubt that a massive amount of volcanic activity in a region named the Central Atlantic Magmatic Province (CAMP) is associated with this mass extinction; what is disputed is by what means did this volcanic activity bring about the extinction of eighty percent of Earth's species. These volcanoes in the CAMP released large quantities of carbon dioxide (CO2) and sulfur dioxide (SO2), among other gases. The carbon dioxide released could have warmed the Earth via greenhouse effects. Alternatively, release of sulfur dioxide is associated with a quick global cooling effect. In a recent paper, Petryshyn et al. don't find evidence of either of these global temperature shifts, meaning that perhaps another mechanism, such as ocean acidification, is needed to explain this extinction.

Reflecting on the super depressing Ceballos et al. paper, the mass extinction event going on right now actually seems pretty reminiscent of the Devonian Mass Extinction Event; both are the result of biotic factors (humans and land plants, respectively). We have this notion that nature is perfectly balanced, but the reality is that living things are really capable of causing massive disruptions in the biosphere. (I'm reminded of this passage in this sci-fi book I read titled Death's End that describes how different the Earth would be if there never was life; living things can really make a difference, for good or for bad!) 

This mass extinction event that we're in is really going to hit future generations hard culturally. I don't mean to get super sentimental here, but biodiversity really contributes to the beauty of the world, and an Earth with a significantly reduced number of species just won't be the same.