Geography of a Super Venus

Question

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?

Answer 1

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.

Answer 2

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.

Answer 3

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.