Formation

We had a few Earth-formation events in the literature lately. After most of our mantle became the Moon, asteroid impacts made the continents. But "impacts" are the limit to what the original article can post in its abstract for 3.6 Gya.

The continent in question is Pilbara now western Australia. There may have been additional hits 3.4 Gya; those seem meteoric. As they note, Pilbara is simply the place they've done the work so far; they might look on to Laurentia and to South Africa.

Now we hear from most of these guys (Christopher L. Kirkland, Tim E. Johnson, Michael I.H. Hartnady, and R. Hugh Smithies): not meteors, but comets. Here we can read the PDF: "Did transit through the galactic spiral arms seed crust production on the early Earth?". This is also Pilbara, with North Atlantic input. A run through the (younger) Milky Way might have perturbed our Oort and perhaps sent (faster) objects directly, with more velocity for the mass.

Either way - as with Theia - the rock or snowball that hit us wouldn't become the body in question - as with our Moon. It stresses a patch of the Archaean crust such that it floats higher than other patches. If big enough it stays floated. I suppose the model is Venus' Aphrodite and Ishtar highlands. Later, when water starts flowing (?back), tectonic forces (?re)emerge.