March 1, 2017 at 4:06 PM
The human handprint on the natural world has become evident in all too many ways in recent decades. The changing climate, the decline of wildlife and the loss of forests and other natural landscapes — all of these factors have led many scientists to conclude that we're living in a new age they've dubbed the "Anthropocene," in which the planet is dominated by human, rather than natural, influences.
Now scientists have presented some stunning new evidence in support of this idea. They've found human activity is responsible for a huge explosion in the diversity of minerals on Earth — possibly the biggest such event in the history of the planet, according to Robert Hazen, a scientist at the Carnegie Institution of Washington's Geophysical Laboratory who led the new research. The last major mineral diversification event is believed to have occurred about 2 billion years ago.
The research team, which includes Hazen and colleagues Marcus Origlieri and Robert Downs of the University of Arizona and Edward Grew of the University of Maine, published their findings Wednesday in the journal American Mineralogist.
"Humans are doing this amazing increase in the number of crystals and the kinds of crystals that occur at or near a surface — and many of these minerals are going to persist for billions of years," Hazen said. "If you're a geologist who came back 100,000 years or a million or a billion years from now … you would find amazing mineralogical evidence of a completely different time."
The International Mineralogical Association (IMA) recognizes about 5,000 different mineral species. Every mineral must have a certain type of crystal structure, and it must be naturally occurring, forming on its own through geological processes. But the strict definition of a mineral may be growing a little hazier, Hazen said.
For one thing, many of the minerals accepted by the IMA originate as a result of human activities, even if they technically form on their own. For example, there are many minerals associated with mining. They form on the walls of mine tunnels or precipitate out of mine water. Others have been found in piping systems or on metal artifacts, and at least one new mineral was discovered in a storage cabinet in a museum, Hazen said.
After an exhaustive look through the 5,000 IMA-official minerals, the researchers concluded that 208 of them are the inadvertent result of human activities.
Additionally, humans have produced a huge assortment of mineral-like crystals through deliberate chemical processes. But they're not defined as true minerals because they didn't arise "naturally." For instance, there are mineral-like compounds produced specifically for use in cement, magnets, batteries, synthetic gemstones and a wide variety of other commercial applications. Altogether, there are tens of thousands of these mineral-like compounds. The Inorganic Crystal Structure Database lists 180,000, the researchers note in the paper, adding: "the Anthropocene Epoch is an era of unparalleled inorganic compound diversification."
There's been some debate among scientists across all fields about when the Anthropocene era began. Climate scientists have pointed to the industrial revolution, which marked the beginning of large-scale greenhouse gas emissions and the rapid, human-caused warming of the atmosphere.
From a mineralogical perspective, scientists are finding human-mediated minerals on structures or artifacts dating back thousands of years. But Hazen added that the biggest diversity explosion "comes with the rise of chemistry about the time of 1800, very close to the industrial revolution — and that's where you see this incredible spike, the greatest diversification of crystals on earth."
The huge human-mediated diversity of minerals is a major way mankind will leave its mark on geological history, but there are other signs humans will probably leave behind as well. For instance, humans are not only responsible for the creation of all kinds of minerals and mineral compounds but they've also been carting them all over the planet. The jewelry business, for instance, has led to the trade of mineral gems all over the world. Thousands of years from now, there will be rubies and sapphires lying around in places they would have never naturally formed.
Human engineering and construction is also likely to leave a permanent mark on the geological landscape.
"The largest impacts are our roads, our buildings, our cities — places where we have huge quantities of transported stones and stone-like materials," Hazen said. These materials will persist, even as they become covered with layers upon layers of sediments over thousands of years, leading to large buried deposits of stone and mineral that only exist in that location because humans placed them there long ago.
Perhaps more than anything, the paper's findings speak to the power and long-lasting influence of human innovation. This effect has manifested in a variety of environmentally destructive ways over the past century from climate change, air and water pollution to sharp declines in plants and animals. But from a mineralogical perspective, there's also evidence of the "boundless" nature of human creativity, Hazen said.
"We're talking about a time of declining biodiversity, but thanks to human ingenuity, we have a time of increased crystal diversity," he said. "In fact, the greatest increase in the history of the globe."