Simanaitis Says

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LET’S TALK ABOUT geology’s time clock. Stratigraphy concerns what can be learned from the order and relative position of rock layers. The word is a Latin/Greek hybrid: stratum Latin for bed and γραφική Greek for graphic. Geologists have already given us an elaborate sequence since the Earth formed some 4.6 billion years ago.


Paleozoic, Mesozoic and Cenozoic Eras are further categorized into Epochs. Note the dates; this neat illustration is most definitely not to scale. Image by Ray Troll from

Beginning some 10,000 years ago, the Holocene Epoch is one of seven epochs making up the Cenozoic Era. These and other stratigraphic markers are identified by radiographic dating, fossils and other means.

Greenforecast, whence Ray Troll’s fascinating illustration, offers an interesting tidbit about fossils: Only about one in 1000 species actually fossilizes. That is, many more species have flourished and disappeared leaving no trace whatsoever in the lithographic (rock-picture) record of life.


Another depiction of eras and epochs is a time-clock, calibrated to show the relative duration of each phase. As is oft cited, humanity’s presence is of extremely short duration, so far.


A sobering spike in Earth’s time-keeping. Image from Science magazine, published weekly by the American Association for the Advancement of Science.

What’s more, ”Anthropocene Pinned to Postwar Period”, by Paul Voosen in Science, August 26, 2016, offers arguments that we live at a geologic cusp, a time when a new epoch might well be started.

Voosen notes in his Science abstract that Anthropocene is already a popular term suggesting humanity’s dominant influence on Earth. The word’s “cene” is patterned after the other epochs; it’s related to our word “scene.” The “anthropo” is Greek: ανθροπο person. Researchers are debating whether Anthropocene should be adopted as a formal name for a new epoch following the Holocene.

Pinning down when to begin the Anthropocene Epoch is not a slam-dunk, however. Several “time spikes” have been suggested:

7000 years ago. Humanity started transforming forests into pastures and cropland some 7000 years ago. Dedicated agriculture might have caused a spike in CO2.

3000 years ago. Humanity’s smelting of lead some 3000 years ago left a traceable record in the environment.

1610. The year 1610 has been suggested because of New World pollen starting to make its way to Europe.

The early 1800s. The beginning of the Industrial Revolution in the early 1800s clearly heralded humanity’s changing the environment.

The Great Acceleration. Most researchers prefer a more recent and easily definable cusp: The Great Acceleration has been used to describe humanity’s attraction to fossil fuel combustion and atomic energy, particularly as recorded in the 1950s’ post-World War II prosperity. Plastics and elemental aluminum are other key indicators of this period.

Also, as noted by Science author Voosen, “Plutonium, from atmospheric nuclear testing, first visible in the soil in 1951, will linger in sediments globally for the next 100,000 years as it decays into uranium and then lead.”

“But perhaps the most promising proxy,” he continues, “comes from recent work that has shown, across 71 lakebeds worldwide, a 1950s spike in fly ash residue from the high-temperature combustion of coal and oil.”

Whatever the choice for a start, 7000 or 3000 years ago, 1610, the early 1800s or the Great Acceleration, the Anthropocene is an appropriate name for such epochal happenings. ds

© Dennis Simanaitis,, 2016

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