An epoch is a division of an era. Geologic epoch changes note irreversible planet history time periods such as the Pleistocene ice age. Epochs can be determined by markers, geological evidence found in core samples and sediment layer studies. Some scientists are proposing naming the latest epoch the anthropocene, but there is discussion and disagreement on when, or if, this epoch began.
The last named epoch is known as the Holocene, an epoch of the Quaternary period of the Cenozoic. It began 11,700 years ago when the last ice age ended. Some of the indications that we are in a new man-driven anthropocene epoch are climate change, nuclear fallout, river diversion, monoculture farming, and ocean acidification. Scientists differ on what marks the anthropocene epoch beginning.
> Some consider the existence of spheroidal carbonaceous particles (SCP) as the best marker for the beginning of the new “human” epoch.These billions of microscopic black balls found from the high arctic to the bottoms of lakes in Chile show up as black parts on core samples where previously most was brown. These incomplete combustion products are leftover carbon atoms which did not pair with oxygen in burning coal and oil and bonded together forming the little black spheres.
This is tied either with the industrial revolution or to the period following World War II, around 1950, when population growth exploded. The need for new housing and automobiles, new products, and more jobs increased the rate of change. New technologies like railroads, turbine engines, and chainsaws enabled humans to become world alterers.
> Another spike of note and possible marker is the radionuclide record. The first atomic bomb explosion in 1945 left its effects, but not in such a global scale as that of climate change.
> Extremely fast species extinction has occurred. Before humans came into being, the planet was dominated by oversized creatures. Almost the next geologic minute, the megafauna was in trouble. By 2050, it is conservatively expected that between 38 and 52 percent of species will be extinct, equal to or greater than past extinction events. Species are being forced to move to adapt while barriers like clear cut forests, urban areas and more paved roads are put in their way.
Even man’s part of the tree has been altered. The sister species, Neanderthal and Denisovans, were wiped out many generations back. More recently it has been cousin great apes. Chimps dropped to half in fifty years, lowland gorillas by sixty percent in twenty years, and Sumatran orangutans are now classified as “critically endangered.” The fewer remaining species, the lesser chance of adapting and surviving.
> On top of extinction, man has created global geographic distribution. Daily, 10,000 species of flora and fauna are moved around the globe in ballast water of ships. This change has happened so fast that in many areas, native plants are outnumbered by non-native plants. Many species become invasive and take over the habitat of the natives, unprecedented in the earth’s history. Thanks to global travel and trade, there are no longer remote islands. On the other hand, islands have isolated some pockets, created by plantations, clear-cuts and road systems.
> A significant marker is the amount of carbon dioxide absorbed into oceans at a very fast rate. From human burning of fossil fuel deposits, 150 billion metric tons of carbon dioxide have been absorbed by the oceans. This ocean acidification can be seen in bleached dead coral reefs. In the Permian-Triassic extinction, 252 million years ago, similarly carbon dioxide dissolved in the sea and turned into carbonic acid, resulting in the vanishing of trilobites and sea scorpions which had existed for hundreds of millions of years.
> An additional possible marker that will endure in strata is microplastic in such quantity that it becomes evidence of mid-20th century Earth system change.
The time period has become known as the “Great Acceleration.” Stratigraphers with the International Commission on Stratigraphy (ICS) are expected to vote in 2016 on whether these markers are significant enough to scientifically categorize the period as a geological epoch, which marker to use as the epoch beginning, and if the name anthropocene, human-dominated, is appropriate. Whatever they determine, the multiple signs of a planet changed by human activity are obvious and likely bode a very different future for Earth.