The geologic timescale. The column on the right is the enlarged top section of the column on the left.
Modified from USGS
Our Earth Is Old!
We know that the Earth is very old. It is more than four billion years old. Scientists figured out the Earth’s age by studying rocks. The rocks that you find near your house, in a park, or at school are all different ages. Some are quite young, made in the past few million years. Others are quite old – many millions or even billions of years old.
There is a special sort of calendar that shows geologic time. It’s called the geologic time scale. The geologic time scale shows the 4.6 billion years of geologic time along a timeline that is divided into sections. Broad sections of time are called Eras and smaller sections of time are called Periods. Having names for the different sections of time helps people talk about when events happened long ago such as when a dinosaur lived, when a volcano erupted, or when an asteroid hit.
Last modified August 20, 2004 by Lisa Gardiner.
Shop Windows to the Universe Science Store!
The Fall 2010 issue of The Earth Scientist
, focuses on rocks and minerals, including articles on minerals and mining, the use of minerals in society, and rare earth minerals, and includes 3 posters!
You might also be interested in:
Scientists are interesting in knowing how many species can fit on the Earth. The number of species is called diversity. If there are a lot of species, then diversity is high. If there are few species,...more
If you went looking for frogs today on the island of Madagascar, the largest one you could find would be just over four inches long. But if you went looking for frogs more than 65 million years ago, you...more
You probably know that dinosaurs are extinct. That means they are no longer alive today. Millions of years before the dinosaurs roamed the Earth, there were plants and other animals alive. There were fish,...more
Scientists have known for a long time that whales, the largest marine mammals, have distant relatives that lived on land millions of years ago. A team of scientists has been searching for fossils to better...more
Sea level is the height of the ocean surface. Scientists measure sea level to figure out how much sea level rise is happening now because of global warming. If you tried to draw a flat line at the top...more
About 250 million years ago, almost all of the life in the sea became extinct. This was during a huge mass extinction. Mass extinctions are when the number of different living things shrinks. Over about...more
Earth is more than four and a half billion years old. But there are very few things around from the Earth’s early days. That’s because our planet is a great recycler. Most of the rocks that were formed...more