C. Radioactive heating of Earths core
Conventional uniformitarian geologists maintain that the earth’s mantle during the Archaean (2.5–4.0 billion years ago) was 100–300°C hotter than today’s mantle. They base this inference on the dominant presence of volcanic rocks called komatiites in sequences of volcanic rocks called greenstone belts. These volcanic rocks are primarily found in the Archaean basement rocks found only on the continents. Those komatiites erupted as lavas as hot as 1600°C, whereas today’s basalt lavas normally erupt at temperatures around 1200°C. A hotter mantle is certainly capable of producing a powerful plume, but the start of subduction and plate tectonics required an ocean floor crust at that time which was old, cold, negatively buoyant, and strong.
