Piacenzian

The Piacenzian is a time period in the international geologic time scale. It is the upper or latest age of the Pliocene, which is part of Earth's long history. The Piacenzian lasted from about 3.6 million years ago to 2.58 million years ago.

This time period came after the Zanclean and was followed by the Gelasian, which is part of the next period called the Pleistocene. Scientists use the Piacenzian to describe important changes in the Earth's climate and the animals and plants that lived during this time.

During the Piacenzian, carbon dioxide levels were similar to what they are today, but the world's average temperature was about 2 to 3 degrees Celsius warmer. Sea levels were also about 20 meters higher than they are now. This makes the Piacenzian a useful example for understanding what might happen to our planet in the future as the climate continues to change.

Definition

The Piacenzian was introduced in 1858 by a scientist from Switzerland named Karl Mayer-Eymar. It is named after the city of Piacenza in Italy.

The beginning of the Piacenzian is marked by certain changes in tiny sea creatures called planktonic forams. The end of this time period is marked by changes in Earth’s magnetic field and the disappearance of some tiny ocean plants called calcareous nannofossils.

Climate

The Piacenzian was a warm time just before big ice ages began in the Northern Hemisphere. Antarctica had smaller ice sheets, and sea levels were about 20 meters higher than today. The world's average temperature was 2–3 °C warmer than before the Industrial Revolution.

During a warm spell called the Mid-Piacenzian Warm Period, carbon dioxide levels in the air reached about 389 parts per million, similar to levels we see today. This time period helps scientists understand what might happen to our climate and sea levels in the future if carbon dioxide levels stay the same. In places like North Carolina and South Carolina, rising sea levels created underwater landscapes. In Namibia, changes in ocean currents led to new kinds of plants growing along the coast.

Origin of the genus Homo

The late Piacenzian period might be when the genus Homo began to develop from its ancestor, Australopithecus. Although the oldest clear fossils of Homo habilis are slightly younger than the Piacenzian, scientists found a jawbone in the Afar Triangle in 2015. This jawbone shows features between Australopithecus and Homo habilis.

This discovery was made near the Mille and Awash rivers in Afar Regional State. The area experienced a big climate shift, turning forests into dry savanna. This change may have played an important role in the evolution of early humans and their relatives.