Himalayas look like jumbled sima pushed together by the collision of tectonic plates, but the middle of Australia does not look like the Himalayas. It is flat, solid rock.

How can you explain the fact that sima is missing on the 70% of the Earth surface? Your article in Space Daily claims that the sial was removed by a glancing collision with a large solid body (giant impact theory). This does not make sense because:
1. Such a collision could not have scraped off more than 30% of the sial.
2. The collision would have produced so much heat that the entire
surface of the Earth would have become perfectly round (perfectly geoid) surface of liquid granite layer of uniform thickness. There would have been no islands or continents after the granite has cooled and solidified.
3. The total amount of angular momentum of the actual Earth–Moon system is insufficient to develop a rotational instability. Attempts have been made to explain the formation of the Moon by its separation from the Earth. It was, however, demonstrated that virtually no possible scenario of this process provides the angular momentum required for their separation.
4. The geochemical compositions of the Earth and the Moon are similar but distinct enough to undermine the giant impact theory.
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