Huronian glaciation

The Huronian glaciation was a time of great change for Earth. It happened about 2.5 to 2.2 billion years ago. During this era, the planet went through at least three separate ice ages. Scientists study these events by looking at a group of rocks called the Huronian Supergroup. These rocks were mostly made from sediment settling in a rift basin. This basin later became a part of the ocean floor. Today, we find proof of the ice in rocks called diamictite. These rocks were formed by the movement of glaciers.

This cold period happened because the air on Earth changed. Long ago, tiny living things called cyanobacteria evolved a new way to make energy. They used a process called oxygenic photosynthesis. This process produced oxygen as a waste product. At first, the oxygen stayed in the ocean or reacted with other things. Eventually, the oxygen filled the atmosphere. This change is known as the Great Oxygenation Event. The oxygen reacted with methane, which is a gas that keeps the planet warm. This reaction turned methane into carbon dioxide and water.

These new gases were much weaker than methane. They could not trap heat as well, so the greenhouse effect weakened. As the air cooled, water vapor fell out of the sky as rain or snow. This made the planet even colder, creating an icehouse effect. Some people think this might have been a "snowball Earth." This is when most of the planet is covered in ice. However, some scientists argue the climate was more temperate. They see different types of rocks mixed in with the glacial ones.

Arthur Philemon Coleman was a scientist who studied these rocks. In 1907, he first suggested there was an ice age in this area. He looked at formations near Lake Huron in Ontario. Because of his work, one part of the Gowganda Formation is named the Coleman member. Most of these specific glacial rocks are found north of Lake Huron. They sit between Sault Ste. Marie in Ontario and Rouyn-Noranda in Quebec. Similar rocks can also be found in Australia and South Africa.

The change in the air was very hard for life. Most living things back then were anaerobes. This means they did not use oxygen and actually found it toxic. The new oxygen caused a massive extinction event. This was the first and longest one in Earth's history. It wiped out many tiny microbial mats in the sea and on land. Later, new life forms that could use oxygen began to grow. These survivors eventually helped lead to the evolution of more complex life.