Earth 2.4 billion years ago was vastly different from what we know today, most notably due to an atmosphere extremely low in oxygen and oceans rich in iron.
The Great Oxidation Event (GOE) Imminently Approaching
About 2.4 billion years ago, Earth was on the cusp of a significant transformation known as the Great Oxidation Event (GOE). This period marked a dramatic increase in atmospheric oxygen levels, but prior to this event, oxygen was scarce.
Atmospheric Conditions
- Low Oxygen: The atmospheric oxygen concentration was less than one part per billion. This is substantially lower than today's levels, which hover around 21%.
- Methane-Rich: The atmosphere was likely rich in methane and other greenhouse gases. This kept the planet warm despite a weaker sun.
Oceanic Conditions
- Iron-Rich Oceans: The oceans contained a high concentration of dissolved iron (Fe2+). In the absence of significant oxygen, iron remained soluble in seawater. This is why ancient sedimentary rocks from this period often contain large deposits of banded iron formations.
- Anoxic Conditions: The deep ocean waters were largely anoxic (lacking oxygen).
Biological Landscape
- Dominance of Anaerobic Life: Life was primarily microbial and anaerobic. These organisms thrived in the oxygen-poor environment.
- Photosynthetic Bacteria: Some bacteria had already developed photosynthesis. However, the oxygen they produced was initially consumed by reactions with iron and other elements in the oceans. The GOE was caused once these materials were fully oxidized.
In summary, Earth 2.4 billion years ago was characterized by low oxygen levels, iron-rich oceans, and a microbial ecosystem dominated by anaerobic organisms, all factors leading up to the Great Oxidation Event.
