The Archaean is the oldest time division in Earth’s extant crustal record. Radioisotope dating gives it an age of 3.9-2.5 billion years, spanning 1.4 billion years, or just over a third of the total length of Earth history. The only remains older than 3.9 billion years are isolated crystals of the extremely hard mineral zircon (ZrSiO₄), which have ages of up to 4.4 billion years. In recolonisation theory the Archaean equates to the first few hundred years immediately after the Cataclysm, at the start of which the planet was under water and new land was forming in place of the old. How well does this idea match up with the evidence?

Water before there was land

The oldest rocks are predominantly igneous – they originated directly from magma rising from the Earth’s interior. They do not tell us whether there was water or not. However, chemical sediments in Greenland from the early Archaean do show the presence of water, and submarine deposition is also indicated by widespread pillow basalts – igneous rocks that contracted into pillow shapes as they came into contact with water. Indeed the rarity of clastic sediments – the sedimentary products of weathering, river action and tectonic upheavals – shows that dry land was rare. The general picture for the early Archaean is of a world that was almost entirely under water, with here and there small volcanic islands protruding like ancient versions of Surtsey Island and rapidly shedding material from their sides.

This agrees well with the recolonisation idea. Early on in Earth history a cataclysm occurred, in the course of which, according to one tradition, ‘the waters prevailed so mightily upon the earth that all the [previously existing] high mountains under the whole heaven were covered.’ Contrary to what one would expect if the Earth had a solar nebula origin, the geological record shows that immediately after the cataclysm the world was dominated by oceans. There was no dry land. With the old creation destroyed, terrestrial crust had to form anew, by massive underwater extrusions.

High ocean temperatures in the Archaean

In recolonisation theory ocean temperatures are expected to have been high, owing to the energy released by the impacts of asteroids, the heat from the granitoids and other igneous bodies that were erupting under water, and (since the true duration of the Archaean was much shorter than 1.4 Ga) the sheer intensity of volcanism at this time.

In the conventional scenario high temperatures are predicted only for the preceding Hadean, not for the Archaean. Massive amounts of heat are thought to have been released during the Hadean by:

• gravitational energy, as the Earth condensed from the primordial nebula that supposedly gave rise to the whole solar system
• a collision with some other planet-sized body that gave birth to the Moon
• bombardment by stray asteroids, interpreted to be products of accretion elsewhere in the solar system, and
• much higher heat production from radioactivity, since the ratio of parent to daughter elements was then much greater.

In such conditions it is difficult to postulate that oceans could have existed at all. Until recently, the absence of rocks older than Archaean was taken to support the idea that the Earth was too hot even for solid crust to form.

But no longer. The discovery of minute Hadean zircons among conglomerates of late Archaean age has obliged a rethink. These crystals are so durable that they can persist even when their parent rock is destroyed, whether by remelting or erosion, and the high ratio of ¹⁸O to ¹⁶O in them shows that the magma from which they crystallised must have been in contact with water. Oceans (probably subterranean) did exist at this time – 400 million years earlier than geologists had thought possible.

The zircons show that the scenario whereby the Earth condensed out of particles of dust billions of years ago is seriously flawed. Recolonisation theory offers a simple explanation for the presence of zircons amongst the conglomerates. They are the remains of the first minerals to crystallise within the Earth’s interior before the cataclysm, at a time when mantle temperatures were rising, not falling. During the cataclysm itself conditions were so violent that all but the most durable minerals in the upper mantle were destroyed; only zircons survived, subsequently mixed in with new Archaean magma.

That may be why the cores of the zircons can be up to a billion years older than their rims: the cores reflect melt coming into contact with subterranean water before the cataclysm (hence localised cooling and crystallisation), whereas the rims reflect a second, post-cataclysm episode of melting and crystallisation as erupted magmas formed new crust in place of the old.

In the Archaean, conventional geology encounters the opposite problem – too little heat. If there were already oceans, and the Sun (as standard cosmology requires) was then radiating 25-30% less heat than it does today, we should expect comparatively low, and over the course of 1.4 billion years steadily declining, ocean temperatures. However, oxygen and silicon isotope data indicate ocean temperatures persisted at high levels throughout the Archaean, declining only in the Palaeoproterozoic. Some therefore speculate that high volumes of methane existed in the atmosphere to act as a greenhouse gas and keep the planet warm.

In reality, sea temperatures were high. Close to newly formed igneous rocks only heat-loving types of bacteria could have survived. Other marine organisms would have been cooked or would have suffocated for lack of oxygen, which becomes progressively less soluble as temperature rises.

Elsewhere, it might have been possible for organisms to survive. To some extent the erupted subterranean deep, coupled with the extraterrestrial waters that fell on the Earth, would have counteracted the heat produced by the impacts. Since the asteroids approached from a direction parallel to the plane of the ecliptic, the bombardment would have been least intense at latitudes close to the then poles, owing to the greater thickness of the atmosphere at angles oblique to the Earth’s surface and the proportionally greater area exposed. In such regions the waters might have been considerably cooler and offered a refuge for marine life. It may also have been there that a solitary vessel, laden with terrestrial animals and a family of human beings, drifted on the seas in the hope that land would be found. They landed, eventually, on an Archaean surface.