Makes a lot of sense, now lets see if the computer testing bears her out.

I'm a geologist, but I have to admit, not a tectonic expert. As a thought experiment, it's quite believable. It seems that an event like this may have caused plate tectonics.

However, I'm not (yet) convinced that we NEED such an event to initiate the plate tectonics we see today.

In the Archaean, the earth's crust was much thinner, and plates were smaller and much more "fragile". Difficult to see subduction happening, although there would have been horizontal movement of crustal plates caused by convection cells in the mantle.

Over time (and we geologists have a LOT of it at our disposal to make things work...) the crust coalesced and thickened. Horizontal movements of the new, increasingly larger and thicker plates, continued. Where they met (and meet) head-on, they crumple up (form structures like the Himalayas), ramp up (obduct) over the other plates (bits of ocean crust can be found obducted into the Alps, and parts of Norway and Sweden), or get pushed under the other part of crust (subducted, like the oceanic crust being pushed under the western coast of the Americas).

Real tectonic experts probably shudder at my explanation, but this is the most simple view. And I do not see the need for an impact event to start it off. In fact I see a contradiction in the thought experiment. On an Archaean Earth, with a thin and patchy crust, how do you develop a big "zone of weakness"?

While I agree with most of what you said, rambler, I'd like to know if you subscribe to any vertical tectonic theories ("sag-duction" being one). While it is almost impossible to prove there was modern-day plate tectonic activity in the Archean, it is quite convincing that there was gravity-driven vertical tectonics, in my opinion. Well, I believe that the subduction in the Archean had characteristics of both.
I find the non-mantle d18O values of the non-mantle d18O values of the Jack Hills zircons to be quite fascinating, though - that's indirect evidence that some form of plate tectonics was alive and kicking 4.3Ga ago.


I was wondering this myself. If there were no plate tectonics prior to this impact, then there would have been a more or less uniform stress regime in the crust. I have no doubt that events like this occured in the Archean, I just doubt that it was one giant astrobleme that kick-started modern plate tectonics. The simplest explanation seems to be that tectonism began as a result of convection in the mantle, in my (always willing to be proven wrong) opinion.