Stage (geology) facts for kids
A stage or age in geology is a period of time. It is measured in millions of years. A stage is shorter than an epoch. It is longer than a chron or chronozone.
A stage is also a group of rock layers. These layers were formed during a single age on the geologic timescale. This usually means millions of years of sediment or rock building. An example of a stage is the Kimmeridgian stage.
Contents
What is a Geological Stage?
Imagine Earth's long history as a giant book. Geologists divide this book into chapters and pages. A geological stage is like a very specific page or a small section of a chapter. It represents a certain period of time when specific rocks were formed.
How Geologists Use Stages
Geologists use stages to organize Earth's past. They look at layers of rock, called strata. Each layer tells a story about the environment at that time. A stage helps scientists talk about specific times in Earth's history. This makes it easier to understand how life and the planet have changed.
Stages and Time
Stages are part of the Geologic Time Scale. This scale is like a calendar for Earth's history.
- The largest divisions are eons.
- Eons are split into eras.
- Eras are divided into periods.
- Periods are broken down into epochs.
- Epochs are made of stages.
- Stages can be divided into even smaller units called chrons.
So, a stage is a smaller piece of time within an epoch. It helps scientists be very precise when talking about events that happened long ago.
Rocks and Stages
When we talk about a "stage" in geology, we are often talking about two things:
- A period of time: This is the actual time when the rocks were formed.
- The rocks themselves: These are the layers of rock (strata) that were laid down during that time.
These rocks are formed through deposition. This is when sediments like sand, mud, or bits of dead plants and animals settle and build up. Over millions of years, these sediments turn into rock. The rocks from a specific stage have unique features. These features help geologists identify them.
An Example: The Kimmeridgian Stage
The Kimmeridgian is a well-known geological stage. It is part of the Jurassic Period. During this stage, a lot of clay was deposited in what is now England. This clay is famous for its fossils. These fossils include ancient marine reptiles and ammonites. Studying the rocks from the Kimmeridgian stage helps us learn about life and oceans millions of years ago.
