This is an image of Venus.
Click on image for full size
NASA/JPL
Volcanic Formations of Venus
One reason scientists think that Venus has a thick crust comes from the shape of the volcanoes of Venus.
In the long time in which the volcanoes exist, there has been no "slumping". Over time, volcanoes slump, like icecream in a dish which is left out too long. An example of slumping is found on Jupiter's moon Callisto.
This means that the crust of Venus is very strong, and cannot be bent, as in the case of the Earth.
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