earth 1: Geological time of the earth, and you, North America and today (v1.0)

Acknowledgement to CNN for this. Geology sounds like a dry technical subject, right? This article makes it interesting by tying it to North America, today and you!!

How does geology mark time?

The geologic time scale provides the official framework for our understanding of Earth’s 4.5-billion-year history. Geologists break down our planet’s history into eons, eras, periods, epochs, and ages — with an eon being the largest chunk of time and an age the shortest. Some well-known past names are the Cambrian, Permian, Jurassic, and Triassic periods.

For example, we currently live in the Meghalayan Age (which began 2251 BCE). It’s part of the Holocene Epoch, which began at the end of the last ice age 11,700 years ago, when ice caps and glaciers began retreating. The Holocene is part of the Quaternary Period (which began 2.6 million years ago), which is the most recent division of the Cenozoic Era (which began 66 million years ago), which in turn is part of Phanerozoic Eon — which spans from 539 million years ago to the present.

Associated with each span is an abundance of information on the biota, environments, tectonics, paleogeography and more. It’s a bit like saying the Middle Ages, or the Renaissance. Every segment in the official timeline is also represented by a single geological site — known as the Global Boundary Stratotype Section and Point (GSSP) — those best captures what’s novel or unique about a particular chapter in Earth’s history. Each point is typically marked with a “golden spike,” that could provide a primary marker for the new geological epoch, often hammered in a pivotal layer of rock — although the site could be a stalagmite or core of ice.

Scientists have collected evidence that a new era has begun, that reflects the impact of humans. There is a proposal to either name it a new epoch (proposed name is Anthropocene and proposed start date as 1950) or a new age. For the Anthropocene, the proposed golden spike location is sediment cored from the bed of Crawford Lake in Ontario, Canada that reveals the geochemical traces of nuclear bomb tests specifically plutonium, large scale burning of fossil fuels and dumping of plastics and fertilizers on land and water bodies. The lake isn’t large, covering 2.4 hectares (5.9 acres), but it is exceptionally deep, nearly 24 meters (78.7 feet), and the sediment found at the bottom can be divided into annual layers to be sampled for geochemical markers of human activity. The shape (of the lake) restricts the mixing of the water column so the bottom waters do not mix with the surface waters. The bottom of the lake is completely isolated from the rest of the planet except for what gently sinks to the bottom.

Geologists will present a proposal to make the Anthropocene official to the Sub commission on Quaternary Stratigraphy later this summer. If the Sub commission’s members agree with a 60% majority, the proposal will then be passed on to the International Commission on Stratigraphy, which will also have to vote and agree with a 60% majority for the proposal to move onward for ratification. Both bodies are part of the International Union of Geological Sciences, which represents more than 1 million geoscientists around the world. A final decision is expected at the 37th International Geological Congress in Busan, South Korea, in August 2024. Naming a new geological epoch is a very conservative process, so there is no guarantee that the proposal will be successful.

Some geologists feel it’s more accurate to describe humanity’s profound impact on Earth as an ongoing geological event rather than a formal epoch with a precise global start date. It’s also possible, they say, that stratigraphers may decide that the Anthropocene doesn’t rise to the level of epoch, but it could be the fourth age of the Holocene — the much less catchy Crawfordian Age.