Paleoproterozoic

Long ago, the Earth was very different. Days were much shorter then. A day was only 20 hours long. There were about 450 days in a year.

The land began to stay in place. Big mountains began to grow, too.

Tiny living things changed the air. They made the air we breathe. This was a very big change.

But the change was hard for some. It made the world very cold and icy. Many tiny living things died out.

New types of life began to grow. They learned to live with the new air. Life on Earth became very diverse.

The Paleoproterozoic was a very long time in Earth's history. It lasted from 2.5 to 1.6 billion years ago. During this time, the land began to stay in place. Huge mountains grew as continents crashed into each other. These crashes helped make a supercontinent called Columbia.

The air changed a lot during this era. At first, the air had almost no oxygen. Tiny life forms called cyanobacteria changed this. They used a way of making food called photosynthesis. This process let out oxygen into the air. This was the Great Oxidation Event. Oxygen levels rose to 10% of what they are today.

This new air was hard for many living things. Most life back then did not use oxygen. The new oxygen was toxic to them. This caused a big die-off. The world also became very cold and icy. This was called the Huronian glaciation.

New life began to thrive after the ice. Some life forms learned to use oxygen to live. These are called aerobes. This era also saw the rise of eukaryotes. These are complex cells that make up modern life. By the end, life was very diverse.

The Paleoproterozoic was a very long era in Earth's history. It lasted from 2.5 to 1.6 billion years ago. This era is the longest one of all. It is the first part of the Proterozoic eon. Scientists divide it into four periods. These are the Siderian, Rhyacian, Orosirian, and Statherian periods. During this time, the continents finally began to stabilize.

The air on Earth changed in a huge way. At first, the air had very little oxygen. It was mostly made of nitrogen and methane. Tiny living things called cyanobacteria changed everything. They used photosynthesis to make food. This process released oxygen as a byproduct. Eventually, oxygen levels rose to 10% of what they are today. This was called the Great Oxidation Event.

This new oxygen was a hard job for life. Most life back then did not use oxygen. To those tiny creatures, oxygen was actually toxic. This caused a massive die-off of life. The world also became very cold during the Huronian glaciation. This was a 300-million-year long icehouse event. It happened partly because methane left the air.

New kinds of life began to grow after the ice. Some organisms became aerobes. Aerobes are living things that can use oxygen. Other tiny life forms lived together in hybrid colonies. This helped eukaryotes, or complex cells, evolve. We see fossils of these cells in North China. They show that life was already diverse by the end. Old fossils also show cyanobacteria in Canada and Australia.

Large land masses also moved during this era. Continents crashed into each other to build mountains. These collisions helped form a supercontinent called Columbia. We see evidence of this in many places. There were mountain belts in South America and Africa. There were also belts in North America and Greenland. Even Siberia and Europe had these big collisions. These events shaped the world we know today.

The Paleoproterozoic Era was a massive turning point in Earth's history. It was the first era of the Proterozoic eon. This era lasted from 2.5 to 1.6 billion years ago. It is the longest era in the entire geological history of our planet. Scientists divide this era into four distinct geologic periods. These periods are the Siderian, Rhyacian, Orosirian, and Statherian. During this long stretch of time, the Earth's continents finally began to stabilize.

One of the most important changes involved the atmosphere. Originally, the air was a weakly reducing atmosphere. It was made of nitrogen, methane, ammonia, carbon dioxide, and inert gases. This mixture was similar to the atmosphere of Titan. Everything changed when cyanobacteria evolved oxygenic photosynthesis. This process released dioxygen, or free oxygen, as a byproduct. This oxygen began to use up the reductants in the ocean and on land. Eventually, these substances like ferrous iron and methane were exhausted. This led to the Great Oxidation Event during the Siderian and Rhyacian periods. Oxygen levels rose from almost nothing to 10% of modern levels.

This shift in chemistry was very difficult for life. Before this, almost all life was made of single-cell prokaryotic anaerobic organisms. These organisms did not need oxygen to live. They used a form of cellular respiration that relied on other chemicals. When free oxygen appeared, it was highly reactive and toxic to these microbes. This caused a massive die-off of the archaea-dominated microbial mats. The crisis was made worse by the Huronian glaciation. This was a global icehouse event that lasted 300 million years. It happened partly because the atmosphere lost its methane, a powerful greenhouse gas.

Life eventually adapted to these harsh new conditions. New organisms called aerobes evolved to thrive using oxygen. They developed bioactive antioxidants to protect themselves. Some anaerobic organisms survived by living in hybrid colonies with aerobes. This symbiotic relationship helped the evolution of mitochondria in eukaryotic organisms. Eukaryotes are more complex cells than prokaryotes. We see the oldest cyanobacterial fossils from this era in the Belcher Islands of Canada. By 1.75 billion years ago, thylakoid-bearing cyanobacteria appeared in Australia. By the late Statherian period, eukaryotic life in North China was already diverse.

Geological activity was also very intense during this era. The Earth saw the development of the first global-scale continent-continent collision belts. These collisions created massive mountain-building events called orogens. In South America and West Africa, these were the Trans-Amazonian and Eburnean orogens. In North America, many belts formed, such as the Trans-Hudson and Penokean orogens. Similar belts appeared in Greenland, Siberia, and Europe. These many collision belts suggest the formation of a supercontinent. This giant landmass is known as Columbia or Nuna.

Scientists have a theory about why these mountains grew so large. They believe the Great Oxidation Event helped cause this mountain building. Increased biomass and carbon burial occurred during this time. This carbon was eventually subducted into the Earth. It is hypothesized that these carbonaceous sediments lubricated the movement of the crust. This lubrication led to crustal thickening and massive mountain ranges. This connection shows how tiny microbes can change the shape of entire continents.

Even the rotation of the Earth was different back then. Paleontological evidence suggests the planet spun at a different rate. About 1.8 billion years ago, a day lasted only 20 hours. This meant there were about 450 days in a single year. This era also saw the formation of the lithospheric mantle in Patagonia. In northern Sweden, felsic volcanism created the Kiruna and Arvidsjaur porphyries. The Paleoproterozoic was a time of extreme change for every system on Earth. It linked the tiny world of microbes to the massive movements of the continents.