I got interested in rock clouds back in February, when I started wondering whether the 15 February Chelyabinsk fireball might have been an outrider in a rock cloud accompanying asteroid 2012-DA14 which made a close approach to Earth on the same day. NASA said the two events were unrelated, but I’m not convinced, particularly since using my orbital simulation model I’ve managed to land a DA14 outrider on Mongolia on the same day.
But it got me thinking about rock clouds in general, and I started looking at how different ones travelling at different speeds behaved in the vicinity of the Earth. And I found that if they were moving fast – more than 5 or 6 km/s relative to the Earth – they’d splatter one side of the Earth with rocks, and the rest of the rocks would barrel off into space. But I also found that if rock clouds came in more slowly – say less than 3 km/s – they’d drop rocks all over the surface of the earth, not just one side. Here’s a rock cloud – actually a line or necklace of rocks – approaching the Earth at 1 km/s, depositing rocks all over it, with the remaining rocks going into orbit around it.
All this reminded me of something I’d first seen when I constructed a transparent globe showing all the Earth’s continents, and found to my surprise that the Pacific ocean covered nearly half the Earth. This was something that hadn’t been immediately obvious in most of the usual maps of the Earth I’d seen in books.
You can see it in the globe on the right, where the faint outlines of the west coast of South America and Antarctica line up fairly nicely with the east coast of Asia and Australia, and the Pacific ocean fills the top right quadrant. Nearly all of the Earth’s continents are on one side of it.
So I’ve begun to wonder whether a rock cloud might have hit one side of the Earth, depositing the crustal continents on top the mantle below. And, since I’d seen that rocks that just missed the Earth would go into orbit around it, I also wondered whether the Moon might have been formed by the remaining rocks that began circling around it.
If the rock cloud had deposited its rocks on just one side of the Earth, it would have had to have been travelling quite fast – greater than 5 or 6 km/s -. But at those speeds, a necklace of circling rocks wouldn’t form. But if the rock cloud came in slower, at 1 km/s or less, it would deposit rocks all over the Earth, and there wouldn’t be any distinct continental mass formed. But at around 3 km/s, it seemed that most of the rocks would have fallen on one side of the Earth, with a lot fewer landing on the far side. And the remainder that missed the Earth would go into orbit around it.
The mass of the Moon is about 7 x 1022 kg, and the total mass of the Earth’s crustal continents is about 2 x 1022 kg, which are the same order of magnitude, and might well be the expected proportions if only a fraction of a rock cloud hit the Earth, and a lot more was captured in orbit around it.
Many comets contain a lot of water, and it has been suggested that most of Earth’s water was gained from comets, so I then supposed that the rock cloud would have been partly composed of water. Just 15% water would have been enough to fill the Earth’s oceans.
So, quite possibly, over a very short time – maybe just a few days – the entire continental crust of the Earth might have been deposited on the Earth, complete with enough water to fill its oceans (which didn’t exist at that time), and mostly on one side of the Earth, much like it is today.
Over the next few million years, the cloud of rocks whirling around the Earth would gradually accrete into a single Moon that gradually sucked all the other rocks into it, a perhaps got plastered with impact craters in the process.
Meanwhile down on the surface of the Earth, the wet slurry of rocks would gradually start sliding around, and water would start trickling out of it and gradually filling the oceans. In fact, at the time of impact, with so much energy being released by rocks hitting the Earth, a great deal of the water might have boiled off, and subsequently fallen as torrential rain. And this rain would fill up the ‘lowlands’ in what is now the Pacific ocean, resulting in a single continent – Pangaea – surrounded by sea. One side of the Earth would be covered in water, and the other side would be covered by the roughly hemispherical continent of Pangaea.
Thereafter, Pangaea would start to gradually break up, with the Americas sliding ‘downhill’ into the Pacific, and land east of Africa spilling outwards ‘downhill’ into the Pacific to form Australia and Antarctica and the Indonesian archipelago. There would probably tend to have been strong volcanism along the coast of Pangaea where it dug sharply into the mantle below, releasing magma beneath. There still is today, in the volcanic “ring of fire” around the Pacific ocean.
There might have been other effects as well. If the Earth had not been rotating when the rock cloud hit it, it may have started rotating afterwards, particularly if the rocks weren’t perfectly evenly distributed over its surface, like a cue striking a ball on one side. And the imbalance of one hemisphere with the other, with far more mass on one side, might have also started it wobbling on its axis.
This isn’t an entirely new theory. It is in fact believed that the Moon was formed from the Earth, because it’s made of very similar stuff. But if that stuff is similar in the composition of the Earth’s crust, it’s possible that it could have been formed from the same rock cloud.
But it’s important to this rock cloud theory that Pangaea was roughly circular and hemispherical. For if Pangaea covered very much less than half the surface of the Earth, it would be hard to explain its formation from a rock cloud, without supposing that was a rock cloud with a radius less than the Earth. But according to one map of Pangaea, it actually did seem to occupy about one half of the Earth’s surface 225 million years ago, and this may have been a long time after it first formed.
There are probably all sorts of objections that could be raised against this hypothesis. If nothing else, it is a catastrophic theory in a time when it is generally believed that geological processes take place very gradually over long periods of time. It proposes that more or less all the Earth’s land masses and seas were dumped on its surface in a matter of a few days or weeks, and quite suddenly provided the necessary environment for life to evolve.
Anyway, last April 1st, I published my new theory of cell growth and division. This April 1st, I offer my new theory of Moon and Earth continent and ocean formation. Next April I suppose I’ll have to come up with yet another idea.