Mobile being is the subject of natural philosophy. . . . Nature is a principle of motion and rest in that in which it is.
— THOMAS AQUINAS, COMMENTARY ON PHYSICS
THE BALL OF THE EARTH CONSISTS OF A SHELL of maybe a dozen discrete plates that bump, bang, rub, and stretch among themselves, riding atop the viscous liquid crystal surface of the underlying asthenosphere. When two plates converge, they may slide smoothly along each other’s margins, but more likely, they will catch and halt. The pressure builds. Then, like a stick bent to the breaking point, they suddenly snap apart, sending out perhaps the hugest and deepest sound in the world. It is so deep that it can’t be heard by human ears; it is experienced instead as motion, vibration, displacement of the ground, collapsing buildings, people and objects thrown into the air, and sometimes even as a pulse of light.
On the moon, there are no tectonic plates. Too small and therefore too low in gravity to possess either an atmosphere upon its surface or the heavier metals in its interior, the moon is a cold, slow lump. But deep inside it is the beginning of a distinction between mantle and core, and at that boundary, moonquakes happen. They propagate rapidly, stirring the sterile dust of the surface, which in places is as much as thirty-three feet (ten meters) deep. It is as though the moon were trying to imitate the Earth.
On average, 150,000 earthquakes occur each year on the Earth. Some are deep-focused in the mantle, and imperceptible at the surface. Others move the soil and the creatures in it with unmatched suddenness and ferocity. When water-saturated sands or clays are put under pressure, the water may force the grains apart, causing solid ground to melt beneath your feet. In 1964, the Good Friday earthquake in coastal Alaska liquefied the sandy soils along the shore, causing hundreds of acres to sink into the sea. If the land is on a slope, it may rush down. The Peruvian earthquake of 1970 sent a landslide down the Andes slopes that buried Yungay, a town of twenty thousand souls, in just a few minutes. In 1971, the San Fernando Valley earthquake in Southern California set off over one thousand landslides in the area. Liquefying fill at the base of an earthen dam was within ten seconds’ shaking of causing the dam to fail, which would have killed tens of thousands downstream.
Up to weeks before an earthquake occurs, however, some change happens in the soil and water. The creatures who live there sense that something is amiss. The Chinese were able to avoid the worst consequences of the Hai-Cheng earthquake of 1975 by taking warning from animals that live in the soil. Though it was mid-February, people observed snakes emerging from their burrows and dying on the frozen ground. Rats abandoned their holes to wander the snowy landscape in groups. Prior to other earthquakes, ants have been observed trooping across the soil surface with their eggs held in their mandibles. Rabbits have been seen hopping on the surface, refusing to enter their burrows. Sheep, cattle, and horses have balked at entering their corrals. Fish jump repeatedly, and shrimp crawl onto dry land.
What do they perceive? It may be that they sense a change in the local magnetic fields. Iron oxides in the soil, formed at different depths in different horizons, have their own characteristic magnetic fields, corresponding to their orientation vis-à-vis the poles of the Earth. It may be that when compression and tension deep inside the Earth bend these fields, the animals who live in or on the soil sense the change directly and respond by flight. This may sound far-fetched, but it is equally probable that pelagic fishes, whales, turtles, birds, and other long-distance navigators constitute the world around them and find their way repeatedly to the exact same compass point, by means of a kind of magnetic proprioception. Even the early Polynesian navigators, who found Hawaii unerringly from the Marquesas across a thousand miles of open ocean, were following currents as their clues, perhaps magnetic currents as well as oceanic.
The Tangshan earthquake of 1976, probably the second most destructive earthquake ever, killed 750,000 people. Just before the first shock, which threw adults six feet into the air, many people observed a bright, incandescent, red-and-white light coming from the area of the epicenter. Afterward it was found that some shrubbery was burned only on the side facing this light.
Is it possible that the tremendous, deep vibration given off by the quake from its focus could heat the soil itself to incandescence, so that it emitted light? A witness to the San Fernando Valley quake, whose house was located near the epicenter, observed a steady glow coming from the earth-fill Pacoima Dam, as though it had become an enormous filament.
James Clerk Maxwell conceived of the universe as an electromagnetic realm characterized by different degrees of conductivity and resistance. Long before it was technically feasible to create loudspeakers or color TVs or electric lights, he accurately demonstrated that the properties of electricity and magnetism would give rise to them. Incandescence, he wrote, occurred when a current passing through a slender wire overcame the resistance of the air around it, causing the air itself to become charged. The repeated excitation of the air released light.
Might it not be that an earthquake does something similar on the scale of the Earth? The tectonic plates, moving and readjusting, cause the Earth for a moment to emit light as though it were the sun.
From the Earth’s point of view, the whole thing may be nothing more than a moment of peristalsis, a readjustment that helps her to digest her food and to relieve herself. But one can’t help wondering what the light is about.
Likewise, the Earth stimulates the moon to shudder and flex, as though she were imparting to her the beginning of a warmer life. A moonquake is caused less by tension between the moons tiny iron core and its surrounding silicate mantle than by the Earth-moon relationship. The strong, deep-focus moonquakes almost all occur within a few days of the moons perigee, its nearest approach to the Earth. The Earth stimulates the moon to shudder and flex. Selene turns toward Gaia like a child at the breast.