Geologic Time
Geologists divide the record of the Earth's past into segments — eons, eras, periods, and epochs — to make studying and understanding billions of years of geologic history more manageable.
Geologic Time: A Metaphor
Geologists estimate Earth is at least 4.6 billion years old. What if all those years were compressed into one calendar year?
Geologic Periods in Kansas
Rocks from all periods are found in Kansas, though some are present only underground.
Understanding How Geologists Talk About Time
Eons and eonothems? Periods and systems? Terms used to describe units of geologic time and the rock layers formed during those time intervals provide a common language for talking about the past.
Mass Extinctions
Mass extinctions, extraordinary events in evolutionary history, have taken place at least five times in the last 500 million years.
