Massasukupuuttoja

Massasukupuuttoja, or mass extinctions, are significant, widespread, and rapid decreases in the biodiversity on Earth. These events are characterized by a large proportion of species on Earth dying out in a geologically short period of time. Paleontological evidence suggests that Earth's history has been marked by several major mass extinction events, with the most famous being the Cretaceous-Paleogene extinction event that wiped out the non-avian dinosaurs approximately 66 million years ago.

Scientists generally recognize five major mass extinctions: the Ordovician-Silurian, Late Devonian, Permian-Triassic, Triassic-Jurassic, and Cretaceous-Paleogene. Each of these events had profound impacts on the subsequent evolution of life. The Permian-Triassic extinction, often called the "Great Dying," was the most severe, eliminating an estimated 96% of marine species and 70% of terrestrial vertebrate species.

The causes of mass extinctions are varied and often complex, involving a combination of factors. These can include catastrophic geological events such as massive volcanic eruptions, asteroid impacts, and rapid climate change, which can be driven by changes in atmospheric composition or oceanic currents. Other contributing factors can be sea-level fluctuations and increased ocean anoxia.

Understanding mass extinctions is crucial for comprehending the trajectory of life on Earth and for assessing current biodiversity loss. While past extinctions were caused by natural phenomena, many scientists believe that current rapid biodiversity decline, often referred to as the sixth mass extinction, is largely driven by human activities such as habitat destruction, climate change, pollution, and invasive species.