Early earth (before 3.5 billion years ago)
Why bother about the early Earth – from c. 4.5 to 3.5 Ga (billions of years ago)? The reason is that all globally-significant events occurred in that time – from the formation of the planet (4.56 Ga), the Moon-forming event and differentiation into the metal core and silicate mantle (>4.4 Ga), enough cooling of the planet by 4.2 Ga to permit oceans (prerequisite for life), advent of plate tectonics (>4.0 Ga), and origin of life (>3.85 Ga). From the planetary perspective, everything else since then is of second-order significance. Rocks surviving from the first billion years are extremely rare, and hold a record of planetary processes when they formed, and via isotopic tracers, the processes back into deepest time, when Earth was born. Focussing on the best-preserved ancient rock record in Isua, Greenland, GeoQuEST researchers are working on evidence for the oldest life, and how it might have affected the early environment and climate.