There is no subduction of the crust of Venus (shown here).
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The Crust of Venus
Unlike the Earth's crust, the crust of Venus is very rigid. On Earth, the lithosphere can be pushed aside in response to the warmth of the Earth. The crust then subducts, melts, and becomes part of the
warm rising magma again. Thus on Earth, the recycling of the crust keeps the crust from becoming too thick.
The shape of the volcanoes suggests that over its history, Venus, like Mars, has built a thick crust. A thick crust prevents motions of p
lates over a surface.
Why would Venus, and not the Earth, have a thick crust? The answer is that unlike the Earth, the rocky material which comprises the crust of Venus does not contain enough trapped water to allow the rocky material to bend and deform (like silly putty).
Thus the crust stays in place and thickens by cooling gradually.
Nevertheless, on Venus, there may be mechanisms for the surface to turn over.
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