To make a long story short: an introduction
Clocks tick away time in a reliable rhythm and dictates the day’s big events: you wake with an alarm, patiently wait for lunch, and rush before important deadlines. On a slightly longer scale, we keep track of our lives in months and years. When we make New Year’s resolutions, apply for our first driver’s license, or vote is determined by an agreed-upon calendar (probably the Gregorian calendar). These divisions of time help to organize our lives.
Conversely, Earth’s geologic time is organized by its major events. Eons, eras, epochs, periods, and ages subdivide Earth’s history into smaller and smaller spans of time, and describe the span between events or changes seen in the rock record. For this reason, each geologic time scale unit is not a predetermined measure of time. For example, since limited geological record remains of the first eon, called Hadean, it is currently approximately 600 million years long and has no official subdivisions. A further complication is that we do not know the exact age of the Earth, so the length of the Hadean may also change. Luckily there is an international standard for the geologic time scale, which is continuously updated as work continues and technology evolves.
So, why Hadean to Holocene? For the last 12,000 years or so we have lived in the Holocene epoch, when modern historic events — some triumphs and others disasters — have been shaped by the geologic past. For example, a major earthquake may change the lives of millions, but the energy released in those few moments may have taken millions of years to build up. This blog is a place to learn about fascinating people, ideas, and events that show us the power of geology and Earth’s long history. I will always post references and/or further reading, to keep the stories as short and sweet as possible. Thanks for reading!
Want to learn more?
- Calendars: History of calendars, BBC Radio 4 story.
- Oldest rocks of Earth: Australian rocks dated to approximately 4.375 billion years old.
- Geologic timeline: relating time and rocks.
