Plate Tectonics and Scientific Discovery
you haven’t seen it, you should read Casey Luskin’s detailed Summary of a recent study arguing for the importance of plate tectonics for advanced life. The basic conclusions of the study are that plate tectonics is important for advanced life in multiple ways and that planets with plate tectonics are very rare. This comports with what Jay Richards and I wrote in The Privileged Planet: How Our Place in the Cosmos Is Designed for Discovery, out now in an expanded 20th-anniversary edition, and what my former colleagues Donald Brownlee and Peter Ward wrote in Rare Earth almost a quarter century ago. But here, I would like to focus on those aspects of plate tectonics that are important for technology.
Plate tectonics is an important part of continent building. Continents provide vast areas of dry land. Dry land is needed to make and control fire, which as Michael Denton argued in Fire-Maker, is the key starting point for advanced technology. Dry land also provides ready access to diverse minerals at or very near the surface, concentrated there by biological and geologic processes, including plate tectonics. Think of gold, copper, iron, uranium, salt, and coal, among many others.
The Continents Hold Other Treasures
There too we find time-stamped archives of Earth’s deep history, where we can dig up fossils and sample ice cores in the polar regions. Some fossils are of ancient sea creatures that died and ended up on the seafloor, covered by sediment, and were later transported to the continents or uplifted by plate motions. Yes, Earth’s dynamic geology destroys much information about its past, but at the same time it preserves often delicate features of ancient life. (See the photo at the top, a fossil leaf from the Eocene, 34 million years old, which I found at the Florissant Fossil Quarry in Colorado. The site is world famous for the quality and variety of its fossils.)
Plate motions also build mountain ranges. Mountains are important for a diverse biosphere. They are also important for mining minerals and for astronomical observations. Mountain ranges greatly increase the exposed surface area, making mineral deposits more accessible. The biggest, most expensive observatories are placed on high mountains to get above most of the mass of the atmosphere. A planet having only tectonics (without plates moving) might have a few high volcanic mountains, but they would remain active for long periods, preventing safe operation of observatories at their summit. This contrasts with, say, the Hawaiian Islands, which are over a hot spot in the crust with the oceanic plate slowly moving over it. The biggest volcano on Hawaii has already moved off the hot spot, causing it to be inactive and serving as a platform for observatories.
The Magnetic Field
Plate tectonics also contributes to the generation of Earth’s magnetic field. The magnetic field serves as a kind of global positioning system. Yes, people have used magnetic navigation for centuries, but I have in mind something more subtle. Geologists use the remnant magnetic field in ancient lava flows to reconstruct the motions of the continents over a large portion of Earth’s history. One aspect of the magnetic field that makes it especially useful to scientists is its semi-regular polarity reversals. This creates a kind of unique bar-code pattern over geologically long periods. It was this pattern, measured on the seafloor, that convinced geologists of the superiority of plate tectonics theory over competing theories in the early 1960s.
Earthquakes and Earthquake Zones
Plate motions generate earthquakes, which generate seismic waves that travel throughout Earth’s interior. Geologists have installed seismometers around the world to measure them and locate the earthquake epicenters and make a 3D map of Earth’s interior. This wouldn’t be possible on water worlds. Remarkably, geologists have discovered that earthquakes overwhelmingly occur in certain restricted regions, namely the crustal plate boundaries. We don’t know when earthquakes are going to happen, but we do know where they happen. Though people haven’t taken full advantage of this information, they could greatly reduce deaths from earthquakes by moving away from earthquake-prone areas.
Plate tectonics is yet another example of the correlation between the requirements for life and the requirements for doing science that we describe in The privileged planet.
