A Short History of Nearly Everything: Chapter 14 Summary & Analysis

In 1971, young geologist Mike Voorhies spots a perfectly preserved rhinoceros skull in the grass in Nebraska while surveying land for a map. Subsequently, he inadvertently discovers what’s now called Ashfall Fossil Beds State Park: a dried-up waterhole-turned-fossil-bed that’s preserving 12-million-year-old animal bones. Voorhies initially thought that the animals were buried alive, but it seems they died from breathing toxic ash and they sought refuge in the waterhole. Curiously, nobody knows where the ash could have come from until geologist Bill Bonnichsen discovers that it matches a volcano in Idaho. It turns out that under Yellowstone National Park, there is a “huge cauldron of magma” that erupts every 600,000 years or so. Bryson says the last time it erupted was just over 600,000 years ago.

Scientists know “amazingly little” about Earth under the surface—we actually know more about the sun’s interior than we do about Earth’s. Earth’s center is 3,959 miles deep. Most mines only go a couple miles deep, which is comparable to barely denting an apple’s peel. In 1906, geologist R. D. Oldham realizes from the angles of seismic shock waves that the waves are bouncing off something deep and rebounding to the surface. From this, Oldham hypothesizes that Earth has a core. Around the same time, seismologist Andrija Mohorovičić discovers similar shock waves in Zagreb, Croatia that appear to rebound off something between the crust and the core. Eventually, Danish scientist Inge Lehman realizes that Earth must have two cores—a solid one surrounded by a liquid magnetic one.

Around the same time, Charles Richter and Beno Gutenberg devise a way to measure an earthquake’s strength (now known as the Richter scale), though a lot of variables—such as the soil, quake duration, and number of aftershocks—affect the actual strength of an earthquake. The largest earthquake ever recorded on the Richter scale is a 9.5 magnitude quake in Chile in 1960 that also set off a tsunami which traveled 6,000 miles to Hawaii. Bryson thinks that the most damaging earthquake happened in Lisbon, Portugal in 1755. Estimated at a 9.0 on the Richter scale, this quake lasted seven minutes and had three aftershocks, killing 60,000 people. In comparison, San Francisco’s famous 7.8 magnitude earthquake in 1906 lasted under 30 seconds. 

There are approximately two earthquakes over 2.0 on the Richter scale on Earth every day. They tend to occur where two plates meet, like at California’s San Andreas Fault. The longer an interval between quakes on a fault line, the more damaging the next earthquake will be. This is worrying for Tokyo, which sits atop the intersection of three tectonic plates but hasn’t seen an earthquake since 1923 (when 200,000 people died). There are also “intraplate earthquakes” that can happen anywhere. In Missouri in 1811, one such quake hits, causing deep fissures from which sulfur poured out. Aftershocks destroyed East Coast harbors. Two subsequent quakes follow, each three weeks after the last. Scientists know little about these except that they’re as “random as lightning.”

In the 1960s, scientists try and fail to drill through the ocean floor off Mexico, but they only get 600 feet deep. In 1970, Soviet scientists try the same thing in Russia’s Kola Peninsula, managing to get 12 kilometers deep (which isn’t even a third of the way through Earth’s crust). Everything they discover is surprising: the sedimentary layer is 1.5 times deeper than estimated, the temperature is much higher than anticipated, and rocks that deep are saturated with water (previously assumed to be impossible). Other scientists who interpret waves that travel through the ground also learn about “kimberlite pipes,” which are like completely random cannonballs traveling from 120 miles deep at supersonic speed, spewing crystals and pulverized diamonds on the surface.

Effectively, Bryson says, we know “very little” about Earth’s interior. So far, scientists assume that there are four layers: a rocky crust, a mantle of “viscous” rock, a liquid outer core, and a solid inner core. They know that the interior is heavier than the crust, and that somewhere inside is a “concentrated belt” of liquid metallic elements which account for Earth’s magnetic field. Everything else is a matter of “uncertainty.”  Scientists know nothing about how the layers interact nor why the crust is much more variable in thickness than typically estimated. Geologists also disagree on how and when the crust originally formed. Viscous rocks move both horizontally and vertically, creating convection currents that move tectonic plates.