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Living in the Anthropocene
Part II

Categories: Science
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Part II

What is the rationale for creating a whole new epoch called the Anthropocene? Is there any reason to think Earth has changed or is changing so much or so fast that we are in a span of time different from the Holocene?

terms for geological time divisionsThe geological time scale was first developed in the 19th century to divide up geological time. This time scale continues evolving as new methods of determining the dates of the rock strata allow for more and more precision. The broadest division of geological time is the era—the Archean is the oldest, and the Cenozoic the youngest. Eras are divided into periods: the Cenozoic is divided into the Paleogene, Neogene, and Quaternary. The Quaternary is currently divided into two epochs: the Pleistocene (pleistos is Greek for “most”) and the Holocene (holo- is for “whole, complete”). The smallest category is the age: the Pleistocene epoch includes four ages—the Holocene, being relatively short, has not been divided into ages. The latest stratigraphic chart (updated in January 2013) [1] places the beginning of the Holocene at 11,700 years ago; that date reflects the end of the last major glacial epoch. Considering that Earth has now been found to be 4.57 billion years old, the Holocene seems a mere blink of an eye.

What has led scientists to consider declaring a new epoch? Why should this be done soon and not a few centuries or millennia from now? After studying the subject, I will try to answer my first question, but I am not sure anyone can answer the second, unless the answer is that humans may not be around long enough to care about such things.

The first half of the 19th century was an important time for people who cared about Earth and how it may have been changing before they were born. Georges Cuvier (1769–1832) helped start the discipline of paleontology, which establishes units of geological time by studying the differences in fossil remains. He also recognized as early as 1812 that some thing or things (presumably floods) had caused mass extinctions. Another Frenchman, Jean-Baptiste Lamarck (1744–1829) developed the theory of inheritance of acquired characteristics. Later, two English friends, geologist Charles Lyell (1797–1875) and Charles Darwin (1809–1882) had the strongest influence on scientific thought for some hundred years, both believing that changes occurred gradually and extermination of species had always been a slow process. Still, the fossil record clearly showed there were periods when flora and fauna of certain types had quite suddenly disappeared, and very different types of critters had appeared practically overnight.

By the latter part of the 20th century, stratigraphers and other geoscientists had proven that major and quite sudden mass extinctions had occurred five times between about 440 million years ago (mya) and 65 mya, and there were many less-drastic extinctions. Now geoscientists and anthropologists are pondering whether we are plunging headlong into a sixth extinction. If so, what is causing it? How fast is it happening? Is it inevitable or can we act to slow, halt, or reverse it? If we are in a new epoch, just when did it begin? These are some of the questions that must be answered.

Let’s look at evidence of how humans have “altered the course of Earth’s deep history,” as expressed by paleontologist Jan Zalasiewicz of the University of Leicester, U.K., and his colleagues [2]. Take human population: huge increases have occurred in a short span of time (about the last two hundred years); with the consumption of fossil fuels, megacities have grown larger and larger; world population may reach 9 billion by 2050. In a record trapped into Antarctic ice that is almost a million years long, we can trace the recent rapid acceleration of chemical and biological effects on Earth. The increase in worldwide temperatures is causing changes that are unprecedented in their extent, severity, and speed, such as the rise of sea levels, species migration and extinction, and ocean acidity.

To name two of the chemical effects lumped together by Zalasiewicz, there are the well-known effects of excessive carbon dioxide on the atmosphere and the fact that black carbon particles, falling out of the air continually and appearing even in Arctic ice, are now classified as a major human carcinogen, in addition to their effect on climate. These were mentioned by Sybil Seltzinger of the International Geosphere-Biosphere Programme (IGBP) when she spoke at AGU.

I had been pondering these subjects for some time, but a very accessible article related to such questions fell into my hands late last month and precipitated my writing this essay. I read the two articles titled “The Lost World,” by the excellent New Yorker staff writer Elizabeth Kolbert [3]. To Zalasiewicz’s list of effects on Earth traceable to human actions she adds another of his favorite subjects—rats. Rats “have followed humans to just about every corner of the globe, and it is his professional opinion that one day they will take over the earth.” Kolbert has expanded her 2009 article, “The Sixth Extinction,” into a book of the same name to be released next month.

My next post in this Anthropocene series will continue on from pointing out some ways humans have changed the Earth to whether we can counteract any of these effects and why we should care.


[1] The stratigraphic timescale:
[2] Zalasiewicz, J., Williams, M., Steffen, W., and Crutzen, P. “The New World of the Anthropocene,” in Environmental Science and Technology:
[3] Kolbert, E. “The Lost World,” in two issues of the New Yorker, December 16 and 23/30, 2013.

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Dynamic Earth: Yellowstone geology doesn’t stay the same

Categories: Science, Thermal features
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Yellowstone Treasures‘s geology writing strives to keep up—

If you were to contemplate nature’s many facets and how quickly things change over the seasons and the years, you might think that you can at least count on the rocks and the mountains to stay the same. Wrong! Geoscientists will tell you that even mountains have their own dynamics. But their rate of change is much slower than humans can easily grasp in their relatively short lifetimes. Nature shapes the land we live on over centuries and millennia, but the rate at which geoscientists learn about it using new methods, ideas, and equipment is constantly accelerating.

Wanting to keep track of all this activity as it pertains to Yellowstone Park for the updated fourth edition of my guidebook, I was delighted when my old friend Dr. Jo-Ann Sherwin offered to bring us up to date about Yellowstone’s geology. I’ve known Jo-Ann ever since she was an outstanding student, whose advisor during her Brown University PhD research was my first husband Bill Chapple. She was the first woman to earn a PhD in their geology department and has gone on to a long career in research and teaching. She also lives in Idaho Falls, convenient to the west side of Yellowstone.

Jo-Ann reviewed the entire book and made numerous suggestions. She also rewrote large portions of our geological history essay, “The Stories in Yellowstone’s Rocks.” Our goal is to make our explanations accurate but concise and as clear as possible without any technical writing. Here’s a short sample from our essay that draws upon recent research into the source and age of the water for the park’s thousands of geysers and hot springs (hydrothermal features):

What makes the different hydrothermal features do what they do? Basically, the great volume of groundwater is heated by very hot rocks quite near the surface at Yellowstone.
There is a very large amount of old groundwater, at least 60 but perhaps greater than 10,000 years old, just above the magma below Yellowstone. The source of this water may have been the glaciers that covered the area or rain and snow in the surrounding mountains, 12 to 45 miles (20 to 70 km) distant. Present-day rain and snowmelt seep down and mix with this old water, become warmed to the boiling point, boil into steam, expand greatly, and find a way to escape upward. Most of the features occur where faults are common, making it easy for the heated groundwater and steam to return to the surface.

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Yellowstone Rock Analysis 101

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mystery rockNot long ago I received a picture of a rock that came from Yellowstone, sent to me by e-mail by a visitor who had picked it up this summer. So I asked my geologist husband to take a look at the picture. Every geologist gets asked frequently to help a friend or acquaintance figure out what some rock is. As you can see from what I wrote to this correspondent, it isn’t all that easy!

. . . I’ve consulted my geologist husband about your rock, and he and I came up with some ideas to pass on to you, but we cannot really answer your question.
I have to say I am very sorry you picked up this rock, since it really is against the law in all national parks to take anything natural out of the park. [Ed.: She later found out that they did not remove the rock from the park.] “Take only pictures, leave only footprints” applies to everyone. However, since you did take it, I’ll send a few comments.
1. If you can remember where you were when you picked up the rock, that would help a geologist determine what it is, since the entire park has been mapped for its geologic history.
2. Are you sure it’s a rock and not something manmade that is highly weathered? It is probably a rock if it’s heavy and dense. Note that a weathered surface may look entirely different from an unweathered one.
3. Were there a lot of rocks that looked like this lying about or only one or two? This would be a clue as to whether it was part of the bedrock of that area or brought there by a glacier or former stream.
4. To properly analyze a rock you have to break it open with something like a sledge hammer against a hard surface and separate rock fragments from anything else.
5. When broken, does the inside look the same as the outside, especially the color? Do the dark bands go through the entire rock?
6. Related to where you picked it up, it may be either a sedimentary rock (probably laid down in layers at the bottom of a sea or lake) or, more likely in Yellowstone, an igneous rock containing magnesium and iron that’s left from a long-ago volcanic eruption.
7. A far-out guess might be that the whitish parts might be plagioclase (igneous feldspar) and the greenish parts, pyroxene or olivine.
The main thing is that a geologist really must both know where it came from and be able to see and physically test it to determine what it is.


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