Updated: Oct 30, 2021
Read the following passage. You have 3 minutes to read the passage. Get your timers or your stopwatch ready to time yourself. The time starts as soon as you begin reading the passage below.
Volcanism and Dinosaur Extinction
While the theory that dinosaur extinction was caused by an asteroid impact 66 million years ago remains prevalent, there is mounting evidence in support of the volcanism theory. According to the volcanism theory, dinosaur extinction was caused by the successive and massive volcanic eruptions that took place in India. There are several pieces of evidence to support the theory of volcanism.
First, the major eruptions of the volcanoes in the Deccan region of India would have emitted enormous gas clouds that would have resulted in climate change. Gas, ash and dust would have covered the sky and, for a time, prevented the sun from warming the Earth. Following this cooling, the carbon dioxide emitted post-eruption would have caused greenhouse warming. Drastic fluctuations from cold to hot temperatures have huge impacts on ecosystems. Furthermore, the sulfur emitted would have caused acid rain and destroyed vegetation. As a result, the food chain would have deteriorated, leaving dinosaurs with nothing to eat.
Around the time of extinction, fossil evidence shows that animal populations gradually declined over time. This steady decline corresponds to volcanic eruption patterns. A marine organism known as foraminifera showed a downturn 300,000 years before mass extinction. If the asteroid impact theory were true, the fossil record might show evidence of sudden mass killing. Instead, the fossil record points to a steady decline of animal life.
Lastly, the dust resulting from volcanic eruptions carries high concentrations of iridium. Iridium was also found at the geological rock layer that marks the mass extinction event at the end of the Cretaceous period. Iridium concentrations were found in rock representing a span of 300,000 years, which indicates volcanic dust emissions of iridium over time.
Now, listen to the Lecture. You may take notes as you listen.
You have 20 minutes to write an essay explaining how the points in the lecture cast doubt on the points made in the reading.
Both the reading and lecture discuss the possible causes of dinosaur extinction.
While the reading says that volcanism was the cause, the lecture disagrees.
First, the reading claims that the gas clouds from volcanoes caused climate change. As a result, the environment shifted causing animals and plants to decline and the dinosaurs to die. However, the lecture insists that volcanoes did not have a significant impact on the environment. In fact, seventy-five percent of the lava eruptions happened after the asteroid hit. Therefore, volcanism could not have been the cause of dinosaur extinction.
Next, the reading asserts that fossil evidence shows support for the volcanism theory.
It shows a slow decline in the number of animals over time. In contrast, the lecture argues that there is evidence in North Dakota that demonstrates there was a sudden mass killing of animals that occurred in that region. Ten minutes after the asteroid hit, evidence of waves and debris was also found. This points to the asteroid as the cause of dinosaur extinction.
Finally, the reading states that the dust from volcanic activity contains iridium. This iridium was found in rock that corresponds with the period of dinosaur extinction. On the other hand, the lecture points out that iridium is not only emitted from volcanoes. It can also come from asteroids. Volcanic eruptions alone are not entirely responsible for the iridium found. Thus, the asteroid theory is a plausible one.
Word count: 239
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