57 pages • 1 hour read
Bill BrysonA Short History of Nearly Everything
Nonfiction | Book | Adult | Published in 2003A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Chapters 13-15Chapter Summaries & Analyses
Chapter 13 Summary: “Bang!”
Bryson opens the chapter by talking about the soft water and strange rocks that were found underneath Manson, Iowa in 1912. The reason for this odd occurrence was later known as the Manson Impact, “the biggest thing that has ever occurred on the mainland in the United States” (190). A meteor had hit where Manson now stands, creating a hole three miles deep and twenty miles across; in fact, the crater would put the Grand Canyon to shame. However, after 2.5 million years of weather and wear, the crater is now flat. While this site doesn’t draw much attention nowadays, Bryson states that in the 1950s “Manson was the most geologically exciting place on Earth” (191).
During this time, meteor crater research was unsophisticated and misunderstood. G.K. Gilbert was the first to hypothesize that the moon’s craters were caused by meteors, but the scientific community at large scoffed at his idea, holding fast to the notion that the moon craters were caused by ancient volcanoes. The meteor craters on Earth were even less understood. For example, Meteor Crater in Arizona, previously Barringer Crater, was incorrectly thought to be formed by an underground steam explosion. It was only when Gene Shoemaker came along and realized that the Barringer Crater was full of fine silicas and magnetites—substances that shouldn’t be there—that scientists started to suspect that the impact came from space.
Asteroids, unlike popular belief, aren’t found in clusters. Instead, these rocky objects float around in loose formation millions of miles away from their closest neighbors. Thought to have been planets that didn’t quite make it, asteroids are abundant in our solar system (some estimate their numbers reach the billions). Asteroids were first discovered in the 1800s, and it was astronomer Gerard Kuiper that systematized and accounted for every observed asteroid. Bryson states that “As of July 2001, twenty-six thousand asteroids have been named and identified—half in just the previous two years. With up to a billion to identify, the count obviously has barely begun” (193).
Asteroids are a concern for the Earth because they are unpredictable, and it’s hypothesized that at least two thousand asteroids big enough to jeopardize civilization routinely cross Earth’s orbit. Even a small asteroid the size of a house can destroy an entire city. On two separate occasions in the 1990s, asteroids nearly collided with Earth, and they arrived without warning. It’s guessed that these near misses could happen as frequently as two or three times a week.
A huge breakthrough in both geology and astronomy happened because of a geologist named Walter Alvarez. While doing fieldwork in Bottaccione Gorge, in Gubbio, Italy, he noticed a thin layer of clay dividing two ancient layers of limestone. Seeking the help of his father, nuclear physicist Luis Alvarez, Walter tested the clay using a process called neutron activation analysis, and found iridium levels were three hundred times normal levels. Considering that iridium is a thousand times more abundant in space than on Earth, Alvarez concluded that the Earth had been struck by a devastating asteroid or comet. Furthermore, he concluded that the dinosaurs had become extinct due to this sudden, explosive event. This became known as the impact theory; however, the paleontological society didn’t accept this theory. Instead, they held fast to their belief that dinosaur extinction was a long, slow process.
Chapter 14 Summary: “The Fire Below”
Bryson opens the chapter by introducing a young geologist named Mike Voorhis, who “discovered one of the most extraordinary fossil beds ever discovered in North America, a dried-up water hole that had served as a mass grave for scores of animals—rhinoceroses, zebra-like horses, saber-toothed deer, camels, turtles” (207). Each of these animals was thought to have died twelvemillion years ago,during the Miocene Epoch. The animals were found buried under volcanic ash, which was curious because there had never been any volcanoes in Nebraska. Today this site is called Ashfall Fossil Beds State Park.
At first, the animals were thought to have been buried alive, but as it turns out they all had hypertonic pulmonary osteodystrophy, which occurs after breathing a lot of ash. Yet, no one knew where the ash had come from, until geologist Bill Bonnichsen found that the ash matched a volcanic deposit from Bruneau-Jarbridge in Idaho. As Bryson puts it, “The event that killed the plains animals of Nebraska was a volcanic explosion on a scale previously unimagined—but big enough to leave an ash layer ten feet deep almost a thousand miles away in eastern Nebraska” (209). As it turns out, there is a gigantic mass of magma, a volcanic hotspot, lurking under the western United States. It disastrously erupts every 600,000 years or so, and today we call this spot Yellowstone National Park.
We know very little about the center of the Earth. Bryson says that if the Earth were an apple, we have barely broken the skin. It was geologist R.D. Oldman who assumed that the Earth has a core because he noted that seismograph readings from an earthquake in Guatemala penetrated he Earth and bounced back at an angle. Seismologist Andrija Mohorovicic noticed a similar phenomenon on a shallower scale, and founded the Earth’s mantle. Another scientist, Inge Lehmann, discovered that the Earth has two cores, while Charles Richter and Beno Gutenberg devised a way to measure earthquakes, known today as the Richter scale.
Earthquakes occur quite frequently, and the most common types happen when two plates meet, as in California along the San Andreas Fault. Bryson describes that “As the plates push against each other, pressures build up until one or the other gives way” (212). The less common but more worrisome type of earthquake is the intraplate quake, which can occur anywhere and at any time. Since these don’t happen near plate boundaries, they are completely unpredictable. No one knows what causes them.
While many scientists have attempted to drill deep into the Earth to study its center, all attempts have failed. As such, the only way to analyze the Earth is to read waves as they travel through the interior.
Chapter 15 Summary: “Dangerous Beauty”
Bryson opens by saying that when most people think of a volcano, they imagine the classic cone shape and the erupting magma and smoke, but there is another type of volcano that doesn’t look like a mountain—these are known as calderas, and they are the most dangerous sort, capable of suddenly exploding and leaving behind a vast pit. This is the type of volcano found in Yellowstone. In fact, all 2.2 million acres of Yellowstone make up its caldera. If Yellowstone blows, the aftermath is unimaginable.
Yellowstone’s first eruption was 16.5 million years ago, and it has exploded a hundred times since. However, the “Yellowstone eruption of two million years ago put out enough ash to bury New York State to a depth of sixty-seven feet or California to a depth of twenty” (227). This ash was responsible for the Voorhis fossil beds from the previous chapter.
A startling discovery was made in Yellowstone in 1973, when suddenly the water levels began to ebb and flow, like what would happen if you lifted one side of a child’s pool and then the other. After a slew of geological testing, it was determined that Yellowstone had a restless magma chamber—which meant that Yellowstone is an active volcano, contrary to the belief at that time. This is how scientists discerned Yellowstone’s eruption cycles, and terrifyingly determined that it is due to explode again, and soon.
Bryson states that even after extensive research, scientists still don’t understand why volcanoes erupt. In fact, they still know little about them at all.
Chapters 13-15 Analysis
Part Four, consisting of Chapters Thirteen through Fifteen, opens with this quote by British geologist Derek V. Ager: “The history of any one part of the Earth, like the life of a soldier, consists of long periods of boredom and short periods of terror.” This quote aptly portrays the tenor of each chapter in Part Four, in that this section is about the dangers inherent to planet Earth. In particular, this section explores the threat of meteors, asteroids, and volcanoes—particularly Yellowstone National Park.
This section is different from the others in that the chapters closely connect to each other thematically. Each chapter assesses the threat of catastrophic natural disasters occurring, and ties it to the past catastrophic events.
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