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LET'S EXPLORE Prehistoric life

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Let's explore prehistoric life

Dinosaurs in North America about 150 million years agoDinosaurs in North America about 150 million years agoDinosaurs in North America about 150 million years agoLife began about 3.8 billion years ago. Since then, many, many different kinds of plants and animals have evolved (see below) and died out. These living things are often called “prehistoric”. The most famous prehistoric animals are the dinosaurs. Over this vast period of time, the Earth itself has changed, too. Mountains have been pushed up and worn down. Even the continents, the Earth’s great land masses, have drifted, very slowly, around the globe.

The Grand Canyon was formed over the past 6 million years as the land in that region started to rise. The Colorado River cut deeply into the rocks to keep its downward flow to the sea. The result is a huge, steep-sided canyon. On either side are layers of rock (sometimes called strata) from different periods in Earth’s history. They get older and older the deeper you go. The lowest layers of rocks are 1700 million years old. Geological history on show in the Grand CanyonThe Grand Canyon was formed over the past 6 million years as the land in that region started to rise. The Colorado River cut deeply into the rocks to keep its downward flow to the sea. The result is a huge, steep-sided canyon. On either side are layers of rock (sometimes called strata) from different periods in Earth’s history. They get older and older the deeper you go. The lowest layers of rocks are 1700 million years old.

A chart showing geological periodsA chart showing geological periodsA chart showing geological periods

Geological time

The Earth is 4.6 billion years old. This extremely long stretch of time is difficult to imagine, so scientists measure events in the Earth’s history in millions of years. This is called geological time. A “recent” event in geological time is the latest Ice Ages, which ended about 11,500 years ago.

The Earth’s history is divided up into geological periods, for example the Cambrian Period (541 to 485 million years ago), the Carboniferous Period (359 to 299 million years ago) and the Jurassic Period (201 to 145 million years ago).

If all of Earth's history were to have taken place in just 12 hours, the Precambrian Period would take up the first 10 hours 30 minutes.Geological periods squeezed into 12 hoursIf all of Earth's history were to have taken place in just 12 hours, the Precambrian Period would take up the first 10 hours 30 minutes.A good way to understand geological time is to imagine the whole 4.6 billion years of Earth’s history taking place in just 12 hours. The Precambrian—the story of the Earth before the Cambrian “explosion” of life 541 million years ago—would take up the first ten and a half hours on the clock. The dinosaurs became extinct (in real life, 66 million years ago) only 9 minutes ago. The entire history of humans would make up the very last second.

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LET'S EXPLORE Prehistoric life

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Let's explore prehistoric life

Geological time

If the entire history of the Earth were contained in 12 hours, the dinosaurs would have become extinct only 9 minutes ago. The story of humankind would make up the very last second.