Earth’s History

The Precambrian period is the longest chapter in Earth’s history, covering almost 88% of the planet’s past. It started about 4.6 billion years ago, wh

The Paleozoic Era lasted from about 541 to 252 million years ago. During this time, Earth's surface changed dramatically. The movement of tectonic pla

Earth’s oceans were full of life during the Paleozoic and Mesozoic eras. In the Paleozoic Era, 541 to 252 million years ago, the seas were home to tri

Imagine Earth’s land as one giant puzzle piece. A long time ago, during the Mesozoic Era, all the land on Earth was connected to one big supercontinen

The Earth's surface is always changing. The Cenozoic Era, which began about 66 million years ago and continues today, has been a time of major changes

Fossils are like nature’s time capsules. They are the remains or traces of plants and animals that lived long ago, sometimes millions of years ago. Th

Fossils are the preserved remains or traces of ancient organisms. They provide evidence of past life and environments. Fossilization is a rare process

Fossils form in different ways depending on environmental conditions and the type of organism. Some fossils preserve hard parts like bones and shells,

Fossils can form in different ways depending on how an organism is buried and preserved. Some fossils keep much of their original structure, while oth

Fossils are like nature’s time capsules. They hold clues about what Earth was like long before people existed. Some fossils show what ancient plants a

Stratigraphy is the study of rock layers (strata) and their formation over time. It plays a key role in relative dating, helping geologists determine

Scientists use geological principles to determine the relative ages of rock layers and uncover Earth’s history. Two key concepts that help geologists

Geologists determine the relative age of rock layers to understand Earth's history and the sequence of past events. Relative dating does not provide a

The geologic time scale is a system scientists use to organize Earth's long history into different time periods. It helps geologists understand major

The geologic time scale helps scientists understand Earth's history by organizing it into different time periods. The Mesozoic and Cenozoic Eras are t

Scientists use natural records such as tree rings, ice cores, and varves to study past climate conditions. These records reveal temperature, precipita

Atoms of the same element always have the same number of protons, but the number of neutrons can vary. Atoms of the same element with different number

Radiometric dating is a scientific method used to determine the age of rocks, fossils, and ancient materials by measuring the decay of radioactive iso