Surface Features (5) ...
Rift Valleys
There are rift valleys on Venus that
are as large as the East African Rift (the largest on Earth). The
adjacent image illustrates a rift valley on Venus
in the West Eistla Region, near Gula Mons and Sif Mons.
The East African Rift on Earth is a consequence of tectonic motion between the African and Eurasian plates.
Large rift valleys on Venus appear to be a result
of more local tectonic activity rather than global tectonic motion,
since the surface of Venus appears to be a single plate.
Meteor Craters
The surface of Venus has been smoothed by recent lava flows and by interaction with the corrosive
atmosphere. However, there are various examples of meteor craters. The following
images show a field of craters and the largest crater found (Mead, which is 275 km in diameter).
All told, about 900 meteor craters have been identified on Venus. The surface is relatively free
of small craters, which is probably due to the dense atmosphere burning up all small meteors before
they can reach the surface.
Tectonic Activity and Surface Age
There is local tectonic activity but the surface
appears to be a single crustal plate,
with little large-scale horizontal motion of plates as
found on the Earth. Why the two planets differ in this way
even though they should have similar interiors is not well understood.
We shall address the issue further in a little while.
Much of the surface of Venus appears to be rather young. The global
data set from radar imaging reveals a crater density consistent with an
average Venus surface age of 300 million to 500 million
years. In sharp contrast to the Earth where the seafloor is younger than the
continents, the lowlands on Venus appear to be older than
the highlands.
