AERLAAN – A playground built for a muse

[PaGaN]

Hey Kacey!

Absolutely there will be islands and archipelagos, just need GPlates to tell me where they are going to be...LOL

Also, fired up GPlates this morning to reconstruct the next 20 mya and discovered that the software has eaten my Rasters! did not load them automatically. I had to find them in the load feature collections dialog and even then they are not showing up GRRRRRRRRRRRRRRR!!!!!!!!!!!!!

I think it might be becasue i imported each raster to a new feature collection when i should probably have saved the rasters to the SAME feature collection.

trying again tonight or, in hindsight, i might load all of the continents together as one TIFF and import as a global raster and then use the polygons to "cookie cut" them to the polygon.

Don't get attached to the present day configuration...this could all change depending on what happens in GPlates...LOL. The plates will be moving according to oceanic rifts spreading and closing so I may not be able to logically get the landmasses where i want them. I'm not overly attacehd to outcomes, so Que Sera Sera.

Also, trying to figure out the best way to add geometry to the reconstruction to show the oceanic ridge formation and spreading. Interested to see how Charerg used flowlines for this purpose.

Good gods, whilst i'm having fun delving into Aerlaan to this extent i'm getting to the point where I'm ready for the tectonics to be over...I WANT TO GET ON TO CLIMATE!!!

Re: naming. thank you It's actually one of the things i enjoy the most. helps to make something a tad more "real". Regarding coming up wiht the names it's actually pretty easy. I keep a Google Keep file with names that come to me. When i'm out and about I just look around and kind of "mashup" words that are around. if i like any then i write them down. you'd be surprised how quickly that list grows...LOL.

PaGaN

[PaGaN]

Okay, so I got GPlates to find and load my rasters! Woohoo! (Phew). Have been messing around with various reconstructions and it's a little tricky getting movements that are believable in increments less than 5my. I think I'm going to have to start editing the .rot file to declare conjugate plates so that certain plates move together until I need them to rift. Bloody Hell this is involved!

(Bangs head on cintiq!)...I know you are feeling my pain Kacey...LOL

PaGaN

[kacey]

I think I'm going to have to start editing the .rot file to declare conjugate plates so that certain plates move together until I need them to rift. Bloody Hell this is involved!

(Bangs head on cintiq!)...I know you are feeling my pain Kacey...LOL

PaGaN

This part is driving me crazy, and yes I feel you're pain. I managed to get plates to move together by editing the .rot file, all you have to do is put the plate id of the plate you want it to follow at the end of the line right before the ! Problem is when you remove the connection for a different time the continent suddenly drops in the animation. I can get them to follow one plate, I just can't for the life of me figure out how to then remove the connection at a specific time and then move them independently without the continent dropping into the wrong spot... if that makes any sense?

[PaGaN]

Yep, unfortunately that makes sense...lol
I think The Astrographers guide covered that though. I think he said you need to add another line in the .rot file to get the desired plate to stay in place and time.

I'll check tomorrow. I'm off to bed!

[Charerg]

Personally I couldn't get the conjugate plates to work either, and I seem to recall I even watched some pretty long Youtube tutorials and some GPlates tutorials about it. I don't recall what the exact issue was though, so maybe I just didn't use the feature properly (despite my reputation, I'm just messing around with GPlates most of the time, rather than being the all-knowing GPlates Guru ).

The easiest way to get the continents to move together is to first just pick up a single continental piece, and decide where you want to start your animation (usually at the date the supercontinent starts breaking apart). In my case, I just picked Central Eocidar, and placed it 200 Mya back at a spot which I thought to be sufficiently far away to reflect 200 million years of movement. I tend to not be too precise with the movements, since you're primarily doing this just to give some basic data and to verify that the idea in your head about the continental movements is actually workable. That's it for this piece of continent: it only has two reconstruction poles: 0 Mya and 200 Mya.

Then you basically pick the next piece, place it accordingly in the supercontinent (in other words, give it a 200 mya pole). Then, decide when it's going to break apart (say, 100 Mya), and simply place it in the exact (or approximate, doesn't have to be 100% precise) same spot within the supercontinent as it was 200 Mya. That's three reconstruction poles: 0, 100 and 200 Mya, and the continent will move with the prior piece until 100 Mya before drifting apart.

Now, if there are shifts in movement or you want the speed of the continent to vary, you'll need more reconstruction poles, but once again I'd recommend keeping it to a minimum. Rememeber that the only real use of a tectonic model is to have an idea where there should be mountains, and in general, give you some geologic data that will be helpful in building the topography. Unless you're building the tectonic model for the sake of having a really amazing tectonic model, you don't need it to be absolutely flawless, just "good enough" will do.


Edit: About those conjugate plates

Now that I thought a bit about conjugate plates, I seem to recall that you needed to add an extra reconstruction pole to the date when the plate drifts apart from it's conjugate. That's because I think it uses the conjugate plate's reconstruction pole while conjugated, if I'm not mistaken, and when no longer conjugate, suddenly jumps to the reconstruction pole of the plate itself. There was some trick to calculating the reconstruction pole of the continent at a particular date, but I've totally forgotten what it was, since I never really used conjugate plates myself.

[PaGaN]

Hey Charerg and Kacey.

So, below is the section from the Astrographer's Guide "Continental Drift the GPlates Way" that seems to specifically talk about conjugate plates:

Next to the time box you will see a set of VCR controls and a slider. Hit the play button or drag the slider to see the continents move. Chances are they’ll slide all through each other. Don’t worry about that yet. I do want two of my present continents to move together until they separate later. Open the .rot file in your text editor.

I wanted the continent represented by PlateID 5000 to move with the continent 3000 until 80.0 million years ago, then start moving on its own. In the row representing PlateID 3000 at 0.0 time set the conjugate plate PlateID to 3000. Now add a new row between 0.0 time and 150.0 time. The time on this new row will be 80.0 and the conjugate plate ID will be 3000. The conjugate plate ID at time 0.0 should remain 0. Save the file, and load it into gplates. Now set the time to 80.0. On the Reconstruction Pole parameters to the right, make sure Highlight Children is checked. Now select PlateID 3000 and drag its pole.

When you Apply the move and Play it, you’ll find that the 5000 continent will move with the 3000 continent until 80.0, then it will jump back to its original position and then jump to its final position at time 0.0. This is a headache. Save the .rot file and open it in your text editor. Copy the 80.0 time row for PlateID 5000 and copy the row between 0.0 and the existing 80.0 time row. Change the conjugate row ID for the pre-existing 80.0 row to 3000. On the new 80.0 row, set the three position coordinates to match PlateID 3000’s coordinates for time 80.0. Now, once you’ve saved the modified .rot file and reloaded it into gplates, the movement should be smoother.

From this it sounds like once you remove the reference to the conjugate plate in the .rot file you have to update the coordinates of the seperated plate to keep it "anchored" at the space and time you want.

I haven't tried this yet but I will tonight. Might just knock up a quick GPlates session with simple geometry until i get this down.

I'm also thinking about ditching the rasters...why? Because when you watch plate reconstructions for Earth (and i have now watched probably HUNDREDS) the plates deform A LOT as they converge and grind against each other and i feel that for a better result I (we?) should try and emulate this. This would also mean that the landmasses would potentially be VERY different to anything expected. If GPlates allowed a raster to deform along with it's linked geometry then it would be awesome but it doesn't (and the software is STILL awesome though...I must be a sadist becasue i'm actually enjoying the brainache and frustration...LMAO).

[Charerg]

Right, so I promised to post something about using flowlines:

So, here's the step-by-step guide:

1. Make some points along the seam between two continents in the process of breaking apart
01 Digitise New Multi-point Geometry.PNG

2. Create Feature and choose "Flowline" from the list
02 Create Feature---Flowline.PNG

3. Next up, choose the appropriate settings. There are three options: spreading centres, left-plate end-points and right-plate end-points
03 Select spreading centres & set up Plate IDs.PNG

Now, a word of warning: choosing the wrong option here will cause GPlates to crash 100% of the time when you attempt to create the feature, and to make matters worse, I don't know if there's any way to know which option is the one that works in any given situation. I've found the spreading centres option to work most of the time, but occasionally left-plate end-points has worked better. In practice, they seem to work in largely the same way, so I'm not entirely sure what the intention behind the different options is (possibly this feature is still a bit WIP, since GPlates gets updates every now and then).

What this means is that you should always save everything before attempting to create a flowline, just in case it does crash.

Ok, moving on...

4. Next, insert an array of time instants
04 Insert array of time instants.PNG

This will have an effect on at which date the "arrows" along the flowline appear. Should become fairly self-explanatory after reading the next step.

5. Save the feature in a feature collection (probably a good idea to have a separate one for flowlines) and view the results
05 Magic.PNG

Finally, assuming everything worked and GPlates didn't crash, you should have a nice flowline appear. Now, keep in mind that since you placed the original points along the seam where the continents drifted apart, this might not 100% match the actual mid-oceanic ridge, because all those strike-slip faults give a bit of wiggle room to oceanic ridges (the shape of the Atlantic Ridge doesn't 100% match the shape of the South American and African coastlines as a result, to give an example).

However, since new oceanic crust is created at equal speed on both sides of the ridge, those yellow dots should accurately depict the position of the ridge, and give a fairly good idea about the shape of the ridge as well.

[PaGaN]

Charerg, you're awesome! Thank you so much. This is useful to ANYONE who is using GPlates for our purposes tough I know Kacey and I will find this of particular immediate importance

PaGaN

[kacey]

These last two posts couldn't have came at a better time, maybe I can actually get some work done now instead of fumbling around in the dark trying to figure out this software. It would be nice to compile all this information into one post for the tutorial section so that other people struggling to get through the learning process of g.plates can have a go to reference when they get stuck. I will admit I'm not the smartest apple on the tree but with the help of the people here I may have actually learned something... Thank you so much. I think these early stage wip threads by people who aren't afraid to show there sloppy beginnings are the most valuable resource the guild has to offer.

[PaGaN]

Hey Kacey.
I agree totally. I think, once we are out of these woods would probably be a good time to consolidate the lessons learned and then write up the tut. We don't know what else we are going to have to familiarize ourselves with before that point...lol.

I'm currently in the middle of a power outage so no mapping fur me at the moment.