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It's common knowledge that the atmosphere of Venus is too inhospitable for a proper landing. The most concerning problem with that is pressure. Venus's atmospheric pressure is said to be 92 times heavier than Earth's. Despite this, according to Basic Planet, Venus boasts some impressive geography:

It does have a lot of volcanic plains with this covering almost 70 percent of the planet. There are two highland areas or continents are they can be known as; one of which lies towards the northern part of the planet and the second is near to the equator of the planet. The north continent is named Ishtar Terra and it is thought to be around the size of the country Australia; and has a high mountain of Maxwell Montes. The Aphrodite Terra is located near the equator and is quite bigger than the north continent which is thought to be around the size of South America.

Though, without there being any lava flow evidence seen on any part of the planet, it has baffled many because with there being volcanic activity, most would have believed lava would have occurred. Though, the planet has to be very young because it doesn’t have a lot of crater impacting the surface which could mean the planet is only around a few hundred million years old.

Due to a lot of volcanic activity, it has helped to shape the surface of the planet and interestingly it is home to hundreds more volcanoes than that on Earth. This doesn’t mean that Venus is going to have a higher amount of volcanic activity than that on Earth but since the crust on the planet is older, there are more volcanic shapes formed. Of course throughout the years, there have been many studies over the volcanic activity on Venus and there have been many programs from Russia throughout the years to note the changes in the planet’s system and how volcanic activities range.

In an alternate universe, Venus is much bigger--175% wider than Earth and 5.5x as massive. Which means an even heavier atmosphere (say, 1200 times heavier than Earth's). Would this extra-extra pressure affect Venus's geography and topography in any way?

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    $\begingroup$ You may have accepted an answer too quickly there, bud. $\endgroup$ – user38070 Jun 17 '17 at 17:02
  • $\begingroup$ Welcome to Worldbuilding, if nobody did that already! While every Stack Exchange site has its own distinct differences, Worldbuilding is “more different” in some ways. In particular, you ought not Accept an answer before waiting at least 24 hours. A full explaination can be found on this meta post. $\endgroup$ – JDługosz Jun 17 '17 at 17:15
  • $\begingroup$ I think the worse issue is temperature, not the pressure. $\endgroup$ – JDługosz Jun 17 '17 at 17:16
  • $\begingroup$ @TotallyN0tABot a4android's answer has so much detail. $\endgroup$ – JohnWDailey Jun 17 '17 at 18:38
  • $\begingroup$ @JDługosz a4android's answer has so much detail. $\endgroup$ – JohnWDailey Jun 17 '17 at 18:38
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Assuming super-Venus has gone through a similar geological history as real-world Venus, then the main differences will be in its atmosphere and its consequent impact on the planet's surface.

The atmosphere of Super-Venus will be significantly hotter and exert more pressure on the planet. This is due to a greatly enhanced greenhouse effect raising the temperature of the atmosphere. The impact of the hotter atmosphere and surface will cause geological features undergo greater amounts of plastic flow than happens to geological features on the surfaces of Earth and Venus. This should make its surface generally flatter.

On the other hand, there will be significantly more volcanic activity. It is to be expected that super-Venus, like its real-world equivalent, will have lost its plate tectonics and there will be no continental drift because of its thicker crust and lithosphere. This means the planet will behave a volcanic pressure cooker kept under heat and pressure until it explodes. There will be a massive outflow of lava sufficient to repave the surface of the entire planet. This is the mechanism responsible for keeping the surface of Venus so young. It is probable that super-Venus may blow its stack more frequency. This again suggests its surface will be generally flat.

Of course, mountain-like features that do arise are most probably volcanoes in the making. best to keep your seismometers handy to warn of any impending eruptions.

In conclusion super-Venus may have a geography and topography very similar to that of real-world Venus only more so.

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  • $\begingroup$ Are you saying that there is a correlation between the runaway greenhouse and the lack of plate tectonics? $\endgroup$ – JDługosz Jun 21 '17 at 6:16
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    $\begingroup$ @JDługosz No. Not directly. It's been a while since I saw this, so this is a very rough explanation: basically how Venus has developed geologically its plate tectonics are stuck because of a lack of water to lubricate them. See point 5 of this FAQ psi.edu/epo/faq/venus.html $\endgroup$ – a4android Jun 21 '17 at 6:44
  • $\begingroup$ Interesting that Google autocompleted venus lithosphere thickness. Earth might have an exceptionally thin crust, because half of it wound up making the moon. Venus might have no plates because the crust is thick. $\endgroup$ – JDługosz Jun 21 '17 at 6:57
  • $\begingroup$ @JDługosz So the Earth is thin skinned! No wonder Professor Challenger was able to make it cry out in "When the World Screamed." $\endgroup$ – a4android Jun 21 '17 at 7:01
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    $\begingroup$ @JDługosz Many thanks for your suggestions to improve my answer. $\endgroup$ – a4android Jun 22 '17 at 5:28
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There are mountains and deep canyons on the bottom of the ocean here on Earth, so it seems that pressure doesn’t matter much. It’s all light as air compared to the pressure underground with the overburden of rock!

The temperature does affect things, as does the gravity and the composition of the air. Much stronger surface gravity will prevent mountains from getting so tall, as under pressure the crust actually flows. Increased heat as on Venus causes rock to flow more readily, so again mountains will be shorter and less rugged.

Lack of water, as on the moon, makes rock stronger, so mountains can be spikier and taller. Other materials in the atmosphere, that gets cycled through the crust, may have effects in either direction.

Now mountains grow due to tectonics. That’s not happening on Venus. Is it happening — and at what rate — on your world? Faster tectonic processes will mean more uplift, more rifts, and also more volcanic mountains.

So, it depends on a lot more about your planet than just the atmospnere.

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Geography and topography are mostly modelled by tectonic forces. Pressure inside the crust is way higher than atmospheric pressure, therefore even a denser atmosphere like the one you declare would simply be peanuts when compared with the tectonic pressure.

However, a denser atmosphere would help containing on a local scale vulcanic eruptions, as hashes and debris would be slowed down quickly.

Also a denser atmosphere could result in more aggressive winds, as dust particles could be easily transported in the air stream.

To summarize: no big differences in instantaneous morphology due to tectonic forces, but quicker changes due to erosion.

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