earth-history

Physics & Space

Earth History & Geology

• Earliest Life: Fossils, Inference and the Road to OxygenThe oldest surviving evidence of life supplies a minimum antiquity, not a birthday. If a convincing fossil is 3.48 billion years old, life was present by then; it may have begun much earlier. Nor does finding life in one habitat prove that life originated there.
• Early Earth: What the Rocks Actually Tell UsA wet planet is not yet a living planet. Before asking how life began, ask a narrower question: what environments were actually available, and how do we know? This is where origin-of-life research meets geology rather than a cinematic reconstruction of a steaming ocean.
• Great Oxidation EventFor much of early Earth history, the atmosphere contained almost no free oxygen. Photosynthetic microbes were producing oxygen long before it accumulated in the air, because oxygen was rapidly consumed by sinks — reduced volcanic gases, minerals, and especially dissolved iron in the oceans.
• The Great DyingThe Permian–Triassic extinction, about 251.9 million years ago, was the most severe known mass extinction. Exact percentages depend on how the fossil record is analyzed, but estimates commonly put marine species loss above 80%, with catastrophic disruption on land as well.