User blog:Cerne/Geology revamp

I thought this entry was going to be about good news, but unfortunately it isn't. It is about yet more setbacks. This time it is about my planet's geology. I did eventually find out more about what the volanoes on my planet would be releasing into the atmosphere by posting about it on the ZBB, but with unexpected results.

It turns out I mis-interpreted a lot of my statistics and what they would actually mean for the planet's physical environment and makeup. In many ways, they turned out better than I thought they did: I found out the difference in gravity would not be all that much more extreme than what we have on Earth, which will mean more predictability and less inconsistencies - or incongruences, if that is a better word - in what I already have planned for the planet in terms of what its flora and fauna will be like. I may need to say goodbye to the giant flying eels, but I don't believe very much else will change (or at least needs to change). My planet actually has a lower mass-to-diameter ratio than Earth does, which results in the lower gravity. This is what I had planned all along so I don't know why it is such a surprise now. Maybe because it has new implications for other things like rotation (I may need to change the length of the day again). Or maybe it was the extent of the difference in gravity that surprised me. I sort of got into thinking that the gravity on my planet was going to be significantly higher, but as it turns out, there may not be that much of a difference after all.

On the other hand, my planet's density may still be greater in relation to its diameter than Earth's density is. Whether or not this changes my previous ideas or not still remains. I had originally planned for my planet to be very metallic and quite radioactive in comparison to Earth, but this may no longer be the case. It changes a few other things as well, namely the presence of a fifth macroscopic regnum (kingdom) of Eukaryotic life forms in my planet's biological taxonomy, the abundance of metal available for the various cultures on the planet to use, the amount of radioactive nuclear energy available for both the indigenous inhabitants and alien visitors, and a key plot device for the story(ies) I plan to tell about the world in the (hopefully) near future.

I think what most affected my vision for the planet was finding out that planets very high in metal don't tend to have a very thin atmosphere. A good analogy would probably be the planet Mercury, which happens to have a lot more Iron and Nickel in it than I had previously thought. So my planet may not have the over-abundance of rare metals that I had been hoping for.

Overall, my inquiry into this matter so far has been quite mortifying (but not in a negative sense) for my initial vision for the planet. I do, however, remember that in order to have a planet that was around 2/3rds to 1/2 the diameter of Earth and yet have a suitably similar gravity - I was actually looking for something just a little bit lighter - I needed to tweak the density and make it more dense than Earth is in order to have the same mass and therefore the same gravitational pull. Now that there is an upper limit, I may need to tweak the density yet again and make it lower while hopefully not affecting surface gravity. Whether this changes what the planet is actually made of or not, I don't know. But there is still some hope left. I now need to find out what my planet's core is composed of: whether it is going to be Iron or something heavier, how centralized it will be, what percentage of metal to silicate rock there will be, and consequently how thick the crust will be.

By far the biggest effect on the planet itself will be the geology; I had anticipated a thicker crust and hence a more Venus-like type of geologic activity (I will explain later) which had in turn led me to envision a very different kind of topography for my maps, but instead it turns out my planet may have plate tectonics just like Earth. That is why I need to find out more about what my planet's density-to-diameter ratio will mean to its interior and consequently to its crust.

If I have a very centralized interior, I may have the thick crust and rare metals in my core that I wanted. If I have a less centralized core, the verious inhabitants on my conworld may have more access to the rare metals that I had wanted them to have. Furthermore, if my metal-to-silicate rock ratio is higher, I may have the higher and more extensive rate of volcanic activity I wanted at the expense of merely having an iron core; such an arrangement would require a less centralized crust tapered in a gradient or dissipated throughout the interior and creating a more homogenous density everywhere. If my metal-to-rock ratio is lower, dissipating or grading the interior's density per cubic metre might halt geologic activity altogether and result in a dead planet. So I would need to centralize the interior. On the plus side, I would have the exotic Venus-like tectonic activity I had initially wanted.

I actually did look further into the tectonic activity of Venus, from which much of my fictional planet was modelled, but first I want to go back to volcanoes. In particular, the volcanic activity on Venus is what influenced the volcanic activity on my planet. Or more rather, gave me a way to put in a very pivotal story arc in the natural history of my planet and the theme of my conworld stories. One of the central characteristics I wanted the planet to have was that of a (relatively) short warm period followed by a longer and much colder period where nearly the whole surface of the planet freezes. It is basically the same idea behind the world of Epona but it uses a different premise to get there.

In the past, I have tried a bunch of different scenarios to bring about such an effect but none of them seemed very viable after a while, for various reasons. I have tried making the planet's orbit more eccentric, I have tried to bring about ice ages naturally in ways that have happened on Earth, I have tried tilting my planet's axis and putting landmasses on both poles to make it more susceptible to ice ages, I tried doing other wierd stuff with Milancovitch Cycles, I have tried hitting my planet with a meteor and putting it off-course, a few times I even considered making my planet a rogue planet (this didn't get very far). I tried cooling periods on a hot-house world, and I tried warming trends on an ice world. I eventually stuck with the latter, and I more recently found out about the effects of volcanism on a planet-wide scale.

I looked at examples on Earth, and I looked at the numerous (and rather typical) examples on Venus. At the time, I had thought - since my planet was going to have sugh a high density for its size - that it was going to have a lot of radioactive elements inside it and hence could produce a lot of volcanic eruptions all at once, heating up the planet and turning it into a hot-house world. This would have worked, had the planet contained a very metallic core, was very radioactive, and had a crust which allowed the kind of volcanic activity I wanted without permitting too much of it and burning the planet out before it had a chance to spawn complex multicellular life. I had eventually decided to move the planet a fair way away from its sun while also making the sun a dimmer spectral type, so it took care of the problem Venus faces now - which is rapidly turning it into a geologically dead planet - by keeping the crust thick and hard. Clearly, from reading this entry, you know that a high metallic core is now probably out of the question unless I want a Mercury analogy. I believe I may still be able to get away with high radioactivity inside the core, but I may not be able to have the high level of volcanism I had hoped for...or I may yet be able to. After all, Venus still is volcanically active, and it is now nearly upside down from rotating so slowly, due to the lack of a magnetic field needed to rotate the planet at a higher velocity.

As has been in the past, density could still be my tweak factor; raising my planet's density should in turn raise the capacity for radioactive elements to exist in its core, like Thorium and Uranium. For there to be a sufficiently high level of volcanism, a lot of radioactivity will probably be needed. Since in my case the upper limit for density will need to be lower, this will mean less of a chance for anything more dense than Iron to exist in my planet's core. Therefore, crust thickness and core centralization must both meet halfway. In a more extreme case, I would need to choose between having a recognizeable core and having any volcanic activity at all. The less extreme the case is, the lower the stakes may be. Just a few thoughts on what I am up against before I continue to look into the problem further. I will probably post here when (or if) I do.

And now onto Venerian (Venus-like) tectonic activity. I received an interesting book for my birthday more than a month ago. Titled Universe and published by DK, this non-fiction encyclopoedia coveres a broad range of areas pertaining to astronomy and our universe in general. Everything from the history of Astronomy to sections on all of the planets, from descriptions of star life cycles and stellar classification to constallation and galaxy identification, this book as been of help to me in designing my own fictional planet. In particular, the section on the planet Venus happened to include descriptions of its geography and various geological formations. Apparently, since Venus' crust is so thick, the plates that make up its crust cannot slide and jostle over the mantle and subduct under one another the way tectonic plates on Earth do; Venus' plates are too thick to do this. So instead of moving horizontally, they move vertically. This probably resembles the process of rifting on Earth in some way, though to a lesser extent, since there is no subduction. The result is a landscape made up of raised and lowered pieces of land and scattered with rifts, chasms, and mountain ranges, not to mention the multitudes of volcano calderas and impact craters that dot the surface.

As such, designating these areas has involved bringing in a collection of new terms to help with the naming process. The book lists a few of them:


 * Terra - A large expanse of land, probably something akin to a continent on Earth.


 * Regio - A smaller expanse of land, probably akin to a subcontinent on Earth.


 * Planum - A high elevation of land, the equivalent of a highland plain or plateau on Earth.


 * Planitiae - a low-lying plain; there may not be an equivalent on Earth, since Venus doesn't have any surface water.


 * Mons - single mountains or volcanoes, probably the result of a "hotspot" in the crust.


 * Montes - Mountain ranges; these probably form on the edge of the landmasses, much like the mountain ranges we have on earth, but more likely due to head-on stress between two plates rather than to subduction.


 * Chasma - A deep, elongated, steep-sided depression, maybe a lot like an undersea vent on Earth.

These terms are used in conjunction with the names of women in mythology and history to name the various areas on the planet's surface. Some examples of this might be Aphrodite Terra, Thetis Regio, Lakshmi Planum, Guinevere Planitia, Maat Mons, Akna Montes, and Diana Chasma. The only exception to this naming scheme seems to be Maxwell Montes but I don't know who named it or who it was named after.

If my planet turns out to have the same kind of tectonic activity, I may designate its various geographic features in much the same way (albeit maybe feigning the whole Women in Mythology/History theme). I will have to see how it goes first, though. I might end up with horizontal plate movement instead.

Anyway, I am going to draw this entry to a close now. I have been working on it for two days straight so I should quit now that I have nothing more to say. I will probably type an update entry, maybe once I have figured out how to use the templates, or maybe not. Thanks for reading.