Quote:
|
Originally Posted by aurorae
Umm, no. Most of Earth has not been resurfaced with Magma. Most of the Earth's surface is sedimentary and metamorphic rocks. It is quite unlike the surface of Venus. The recent geologic histories of both planets are very different (hard to say what the early geologic history of Venus was like, as the evidence has been removed).
|
When I mentioned that the Earth has also been resurfaced with magma, I was referring to the new ocean crust formed from basaltic magma extruded along oceanic spreading centres. You are right, though. The Earth has for the most part not been resurfaced, but rather new surface has been added.
My underlying assumption is that planetary expansion can have different forms in different cases. On the Earth it appears to be associated mainly with seafloor spreading, but basalt flooding (e.g., Siberian traps) may also have played a role. On Mars it also seems to have been mostly a process analogous to seafloor spreading. On Venus, it might have occurred through basaltic flooding. As you say, basaltic flooding removes traces of the earlier history, and so we lose some of the possible evidence of expansion on Venus (that we seem to have on Mars and Earth).