Reading the Rocks Quotes

“According to pioneering microbiologist Lynn Margulis, "fully 10 percent of our own dry body weight consists of bacteria, some of which, although they are not a congenital part of our bodies, we can't live without." In fact, a healthy human body has more bacterial cells than animal cells (bacterial cells are far smaller). Our own bodies are in some ways microcosms of the biosphere as a whole.”
― Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth

“With each integer on the Richter scale, there is a tenfold increase in the number of earthquakes that occur annually. On average, there is one magnitude 8 event, ten magnitude 7 events, a hundred magnitude 6 events, and so on, each year. If we consider this from an energy standpoint, the smaller earthquakes account for a significant fraction of the total seismic energy released each year. The one million magnitude 2 events (which are too small to be felt except instrumentally) collectively release as much energy as does one magnitude 6 earthquake. Although the larger events are certainly more devastating from a human perspective, they are geologically no more important than the myriad less newsworthy small ones.”
― Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth

“A recent analysis of satellite imagery, for example, has shown that the total "constructed" area in the continental United States is now equal to the size of the state of Ohio. Never has so much of the Earth's surface been covered by materials designed to be impervious (concrete, pavement, buildings). These surfaces not only decrease the proportion of precipitation that soaks into the substrate to become groundwater, but also change the reflectivity, biological diversity, and carbon storage capacity of the land. Not all of these changes are necessarily bad, but they will interact in subtle and unpredictable ways with other environmental changes, both natural and human-induced.”
― Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth

“A retrospective of how scientific perceptions of the Earth have changed over the past three centuries reveals a strong correlation between Western political and social views and contemporary scientific “truths.” This connection should make us suspect that our understanding of the planet at any historical moment is at best incomplete and at worst hopelessly wrapped up with our own self-image.”
― Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth

“Is it more comforting to think that the Permian catastrophe was caused by the unlikely convergence of a series of events or by a single nefarious villain? In a time when anthropogenic emissions of sulfur and chlorine match or exceed volcanic releases, when human carbon dioxide production outstrips natural rates by a factor of ten, and when growing areas of the world's oceans are becoming dead zones as a result of sewage and fertilizer runoff, I'm not sure. More recent records of climate instability are equally sobering.”
― Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth

“If we extrapolate this rate of overturn back in geologic time, the ocean floor has apparently been rejuvenated at least two dozen times since the Earth formed. When Earth was younger and hotter, however, the pace of convection may have been faster, and the ocean floor may have been resurfaced more frequently. But this leads to a conundrum: If convection had been faster in the past, as most geoscientists think it was, ocean crust would have arrived at subduction zones at a younger average age, still too hot and buoyant to be assimilated back into the mantle. This suggests that true plate tectonics, with rigid crustal slabs, efficient recycling of ocean crust via subduction, and water-assisted production of low-temperature melts, may not have occurred on the early Earth. Instead, plate tectonics could begin only when the Earth had reached a degree of thermal maturity, probably about 2.5 billion years ago (around the close of the Archean eon and the beginning of the Proterozoic). Before this, Earth's mixer settings—and the extent to which surface water was stirred back into the interior—were probably different. We can look to rocks formed in these distant times, Earth's record of its childhood and youth, for clues.”
― Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth

“…so far, the rocks haven’t provided enough information for geological detectives to distinguish events that may have happened over thousands of years from those that happened over millions.”
― Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth

“The rate of rebound reflects how fast the mantle beneath the crust can flow back into place, and in places the rate is surprisingly speedy. The northern half of Lake Michigan, for example, is tilting upward at a rate of about 1 millimeter per year, spilling slowly over Chicago.”
― Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth

“Finding outcrops is easy in arid and mountainous areas, where naked rock lies basking in the sun. But in humid and topographically subtle areas (think Indiana), outcrops are elusive. Invariably, the few rocks that do expose themselves become veiled with lichen over time (the resourceful geologist learns to note that certain colors of lichen signify particular rock types—orange for basalt, green for granite)”
― Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth