Question

what was a significant effect of the great oxidation event on earths atmosphere?
decrease in hydrogen
decrease in nitrogen
increase in oxygen levels
increase in carbon dioxide

Explanation:

The Great Oxidation Event, occurring around 2.4 billion years ago, was driven by cyanobacteria producing oxygen via photosynthesis. This led to a dramatic, permanent rise in atmospheric oxygen, which is its defining and most significant atmospheric effect. The other options do not align with this event's core impact.

Answer:

Increase in oxygen levels