Australia: The Land Where Time Began

A biography of the Australian continent 

The Habitats of Early Life – Processes on the Young Earth

According to Arndt & Nisbet conditions at the surface of the young earth (Hadean and Early Achaean) were suitable for the emergence and evolution of life. They suggest that surface temperatures in the Late Hadean may have been clement with an atmosphere of greenhouse gases above a planetary surface that was dominated by the ocean. Arndt & Nisbet suggest the first crust was mafic and it repeatedly melted internally, producing the felsic rocks that crystallised the zircons of the Jack Hills. During late heavy bombardment this crust was destabilised, with plate tectonics initiation soon after, to produce voluminous crust by the Mid-Archaean, though the volume of the ocean were sufficient to submerge much of this crust. Around abundant komatiitic volcanism in the Hadean and Early Archaean hydrothermal systems may have provided suitable sites to host the earliest living communities, as well as the evolution of key enzymes. It is suggested by evidence from the Isua Belt in Greenland that life was present by 3.8 Ga, and the geological record in the Pilbara, Western Australia, and the Barberton Greenstone Belt, South Africa shows that there was abundant microbial life, which probably used anoxygenic photosynthesis. Oxygenic photosynthesis had evolved by the Late Archaean, which transformed the atmosphere and allowed the evolution of eukaryotes.

Sources & Further reading  

Arndt, N. T. and E. G. Nisbet (2012). "Processes on the Young Earth and the Habitats of Early Life." Annual Review of Earth and Planetary Sciences 40(1): 521-549.