

Volcanoes on Venus? Lava may still flow on mysterious planet - danboarder
http://www.latimes.com/science/sciencenow/la-sci-sn-venus-volcano-lava-20150619-story.html

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sqeaky
I had heard we thought there were no plate tectonics on Venus because it had
no water to assist sub-crustal flow.

Are these results accurate? Does it mean Venus has Tectonics ? Does it mean
water is not required?

I really don't know much about it I am just a curious armchair geologist.

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jofer
Planetary geologists have strongly suspected that Venus was active in some way
since the various US and Russian missions in the 80's/90's. There's a ton of
clear volcanic features on Venus. Past missions have seen hints (variable SO2
levels) that volcanism might be active today, as well.

However, active volcanoes don't require Earth-like plate tectonics.

The current thought (unchanged since the late 80's early 90's) is that most of
Venus's surface is about the same age and dates to ~300-500 million years ago.
That's very young compared to the rest of the solar system other than Earth.
It appears to have undergone a more-or-less complete resurfacing at around
that time.

In addition to volcanoes, there are a number of topographic features
consistent with relatively recent deformation (basically, lots of big cracks
and some compressional wrinkles). However, there are no clear plate boundaries
as Earth has.

The current thought is that Venus's deformation and volcanism is directly
driven by mantle convection. Earth's plate tectonics is actually mostly
subduction driven. There's a lot of horizontal motion of plates on Earth. On
Venus, there's not a huge amount of horizontal motion on the surface (there's
clearly no subduction on Venus). The thought is that there's no athenosphere
(very weak, thin layer in the mantle with 1%-5% melt) on Venus to allow large
horizontal motions.

Interestingly, Venus might be a decent analouge to what pre-plate-tectonic
Earth was like. (That part is just my speculation, and I'm not a planetary
geologist, so take it with a grain of salt.) Proper plate tectonics probably
didn't begin on Earth until around 2 billion years ago (the details are still
hotly debated). Prior to this time, subduction doesn't seem to be occuring,
and there's not much evidence for large horizontal motion.

At any rate, this is just another piece of evidence that Venus's volcanism is
still at least somewhat active today, as opposed to all dating to ~300Ma.

Incidentally, I just realized that there's a GSA Today article from last year
that (briefly) summarizes Venus's geology. GSA Today articles are meant to be
very easily readable and only semi-technical (i.e. assumes only general
geologic knowledge). It's well worth a read, if you're intested:
[http://geology.gsapubs.org/content/42/1/95.full](http://geology.gsapubs.org/content/42/1/95.full)

~~~
sqeaky
Thank you. I do not know why but volcanoes and tectonics were intrinsically
linked in my thinking. You have demonstrated that the possible mechanisms for
surface geological activity can be so varied that this implicit assumption was
completely unfounded. I will be reading more on this.

