Eleventh century Chinese naturalist Shen Kuo (沈括) wrote about the concept of deep time-- what we now refer to as geologic time.
The geological or deep time of Earth's past has been organized into various units according to events which took place in each period. Different spans of time on the time scale are usually defined by major geological or paleontological events, such as mass extinctions. For example, the boundary between the Cretaceous period and the Paleogene period is defined by the the demise of the dinosaurs and of many marine species. Each era on the scale is separated from the next by a major event or change. Eras are measured in hundreds of millions of years. An epoch, a subset of an era, is measured in tens of millions of years.
The National Academy of Science, in an expert consensus report, recently identified the beginning of a new epoch in deep time. This epoch is one where where human activities will largely determine the evolution of Earth’s climate. The report says, in part, that "because carbon dioxide in the atmosphere is long lived, it can effectively lock the Earth and future generations into a range of impacts, some of which could become very severe. Therefore, emissions reductions choices made today matter in determining impacts experienced not just over the next few decades, but in the coming centuries and millennia."
Are we paying attention yet?
photo: near Grindelwald, Switzerland, copyright Bruce Behnke, 2010