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South African rocks uncover Earth's violent oceans 3.6 billion years ago
Ancient rocks from South Africa offer striking glimpses into Earth's turbulent early days, painting a picture of a world ruled by expansive oceans, fierce volcanic activity, and the faint stirrings of life amid relentless geological chaos.
Geologist Simon Lamb from Victoria University of Wellington has devoted years to studying the Makhonjwa Mountains in South Africa and neighboring Eswatini, where rocks aged 3.2 to 3.6 billion years hold preserved details of our primordial planet. His findings, outlined in a new book released this month by Columbia University Press, reveal a dramatically different Earth from the one we know today.
These ancient formations expose a planet blanketed in vast oceans with nonstop volcanic eruptions on the seafloor. Deep beneath the crust, temperatures ran far hotter than now, producing unusual white-hot magma loaded with elements from the planet's core. Massive surges of superheated water burst from underwater fissures, forming towering chimneys rich in precious metals.
Life already thrived near these hydrothermal vents, where microbial mats formed in sheltered coastal waters. Periodic massive earthquakes rattled the rocky foundation, sparking underwater landslides that plunged into ocean depths. Giant asteroid strikes rocked this world but crucially failed to wipe it out.
The atmosphere carried a deadly brew of gases, heavy with methane and carbon dioxide but devoid of oxygen. These greenhouse gases kept surface temperatures suitable for liquid water, despite a much fainter Sun. Early life took the form of anaerobic microbes, possibly displaying vivid pink or violet hues.
Modern Oceania in the southwest Pacific mirrors this ancient scene most closely, according to Lamb. The 2022 eruption of the Hunga volcano near Tonga produced a mushroom cloud reaching into space, packing the force of a 60-megaton atomic bomb and unleashing over 192,000 lightning strikes.
Experiments confirm that such lightning can spark the creation of basic organic molecules essential for life. Millions of similar eruptions on early Earth would have provided countless chances to kickstart life's chemistry in submerged volcanic craters.
Earth turned blue within the first tenth of its history. Mars and Venus may have started similarly, but our planet sits squarely in the Goldilocks zone, receiving just the right solar energy to dodge a scorching hellscape or frozen wasteland.
