Historical geology facts for kids

Diagram of Earth's long history.

Historical geology is a part of geology that helps us understand the Earth's past. It studies how the Earth's surface and rocks have changed over millions of years.

Geologists use special methods like stratigraphy (studying rock layers) and paleontology (studying fossils). These methods help them figure out the order of events and what plants and animals lived at different times. They first learned the sequence of rock layers. Later, the discovery of radioactivity and radiometric dating helped them find the exact ages of these rock layers.

Thanks to these tools, we now know when important things happened in Earth's history. The Earth is about 4.567 billion years old! This incredibly long period of time is called deep time. Scientists have divided deep time into different units. The boundaries between these units are often marked by big geological events or major changes in life, like mass extinctions. For example, the end of the Cretaceous period and the start of the Palaeogene period is marked by the event that wiped out the dinosaurs and many ocean species.

Understanding Earth's geological history is important for finding energy sources and valuable minerals. This knowledge also helps us prepare for dangers like earthquakes and volcanoes.

Understanding Geologic Time

Scientists use special terms to talk about Earth's long history. The biggest time unit is a supereon, which is made of Eons. Eons are then split into Eras. Eras are divided into Periods, which are further broken down into Epochs and Stages.

When talking about rocks, geologists often use terms like "Upper," "Middle," and "Lower." For example, you might hear "Upper Jurassic sandstone." "Upper" means the younger rocks from that period. When talking about time, they use "Late," "Middle," and "Early." So, "Early Jurassic deposition" refers to events that happened early in the Jurassic Period. These words are capitalized when they refer to a formally recognized part of a time unit, like "Early Jurassic."

Sometimes, the same time period was given different names in different parts of the world because the rocks and fossils looked different. For example, the Lower Cambrian period in North America was called the Waucoban series. In East Asia and Siberia, the same time was split into Tommotian, Atdabanian, and Botomian stages. Today, groups like the International Commission on Stratigraphy work to create one universal time scale that everyone can use.

Table of Geologic Time

This table shows the main events and features of the different periods in Earth's history. Remember, the height of each row does not show how long each period lasted.

Related pages

• History of the Earth
• Age of the Earth
• History of the geologic time scale

See also

In Spanish: Geología histórica para niños