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I've been doing a lot of research lately on my binary planet system for the series I'm writing. Some details I've already worked out:

  • The system's star is 0.6 solar masses, 0.8 solar radii and 0.3 solar luminosities, making it a K-dwarf.
  • My planetary system is orbiting 0.5 AU from the star with nearly no eccentricity.
  • Both planets are earth-like in size and ability to support life. They are tidally locked, each with one side always facing the other.
  • The planets are roughly 10x closer to each other than the moon is to earth. With that and being earth sized, the planet appears about 37x larger in the sky than our moon does at the nearest point. (This is outside the Roche limit.)
  • Because the planets are tidally locked to each other, tides are solely caused by the sun. Due to the size and proximity of the K-dwarf star, tides on each planet are approximately 1.5 times the magnitude of the tides on earth (from the sun and moon).
  • The incredible constant pull each planet has on each other results in massive bulges centered on the equator at the points closest to and furthest away from the other planet. This bulge (assuming I've done my math right) has a height equivalent of a tide 56,462.43x stronger than a tide on earth, which at its high points would be 33,808 meters deep, or nearly four Mt. Everests deep.

I have other information that I don't think is relevant to my questions. If someone thinks other information is needed to answer or provide as useful context, let me know.

My main question is this:

Could a land mass realistically exist above water at a point on one planet that is closest to the other planet (where the water would typically be deepest)?

No matter what I do for my books, I need there to be people living around this area, so if I have to make it a floating island of some kind I will. I've considered a massive breakoff from a bayou or a modified pumice floating island, but those don't really satisfy my desire for a real, massive, island that actually connects to the ocean floor and has its own volcanoes. So, would it be reasonable for land to form basically 4 Everests high, enough to break out of water at the highest point in its bulge? If not, I'll need to come up with another way to have a land mass there.

Thanks for any and all comments! If there are any questions for me, just let me know!

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    $\begingroup$ Welcome to WorldBuilding! I don't see why the magnetic fields would be so much different from the magnetic field of Earth alone. 38,000 km is very very far away for a weak magnetic field such as Earth's; the strength of the magnetic field of the other planet would be basically undetectable on the surface of this planet. But... The rules of the site require one question per question, and we generally do not like fishing for ideas or requests for unbounded lists. See the help center and take the tour for a gentle orientation. Please edit the question to make it conformant to the expectations. $\endgroup$
    – AlexP
    Commented May 8, 2021 at 20:02
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    $\begingroup$ @AlexP Thanks for your reply! I have edited my post to limit it to asking about a single issue and removed the parts asking for other ideas. I appreciate the help! $\endgroup$
    – Ray Lawler
    Commented May 8, 2021 at 21:12
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    $\begingroup$ Why would the water be deepest? The tidal force works on the bulk of the planet the same as it works on the water. Tides produces by the Moon and the Sun affect only the water because the the tidal force moves much too quickly for the crust and mantle to respond; but a constant tidal force would, over long enough time, pull the body of the planet into equilibrium. (P.S. and you will have an equal bulge on the opposing side... That's how tidal forces work.) $\endgroup$
    – AlexP
    Commented May 8, 2021 at 23:35
  • $\begingroup$ @AlexP I had accounted for the bulge being on both sides, and thought about it affecting the crust and mantle, but for some reason assumed the math I did only applied to the ocean water. I knew my planets would be somewhat egg shaped, but didn't think about that making up for a significant portion of the 34km difference. I suppose it's probably reasonable to assume the land mass I want is at least possible given a variety of different factors, like the age and composition of the planets. And if not, very few people will know, especially because I won't be writing about these details. Thanks! $\endgroup$
    – Ray Lawler
    Commented May 9, 2021 at 2:50
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    $\begingroup$ Look at the example of Earth. Earth has an equatorial bulge due to the centrifugal force. The bulge affects the land masses just as it affects the ocean. $\endgroup$
    – AlexP
    Commented May 9, 2021 at 13:20

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Let's take a look at this.

As AlexP points out, tidal forces work on both the water and the crust. So we don't really need to worry about it being a huge amount deeper on that side.

But if that's not enough, we have a secret weapon...

Volcanoes

Volcanic islands should be able to make you some nice islands even in places where the water is deeper. In fact, I'd expect there to be more volcanic action than, say, on Earth because the tidal forces are messing with the crust (though I'm not a volcanologist, so take that with a grain of salt).

Just imagine: Hawaii (volcanic islands) with a beautiful view of a planet taking up 37x the amount of sky the moon does. I'd say the tourism industry would be pretty strong to a place like that. I know I'd pay for it. ;)

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