anoxic events

Anoxic events are periods in Earth's history when large areas of the oceans became completely depleted of oxygen, a condition known as anoxia. Without oxygen, most marine life can't survive, leading to mass extinctions and the preservation of certain sediments as fossils. These events often occur due to factors like increased nutrient runoff causing excessive algae blooms, which decompose and consume oxygen, or changes in ocean circulation that limit oxygen supply. Anoxic events can last thousands to millions of years and significantly impact the planet’s biological and geological history.