## Working with the Conjugate Plate in GPlates

As promised last week, we are now going to demonstrate the usefulness of the conjugate plate in gplates.

I’m going to start with just the two lines preparing plate 100. To that I will add another pair of lines defining new plates 101, 102 and 103, which have plate 100 as their conjugate plate.

100  0.0   0.0    0.0    0.0  000 !1

100 150.0   0.0    0.0    0.0  000 !1

101  0.0   0.0    0.0    0.0  100 !Chris

101 150.0   0.0    0.0    0.0  100 !Chris

102  0.0   0.0    0.0    0.0  100 !Tom

102 150.0   0.0    0.0    0.0  100 !Tom

103  0.0   0.0    0.0    0.0  100 !Mary

103 150.0   0.0    0.0    0.0  100 !Mary

I’ll draw up a quick coastline in gplates and give it the PlateID of 100. I will now define three points using the Digitise New Multi-point Geometry M tool. I’ll  call them Chris, Tom and Mary. Maybe we’re chronicling the travels of three very slow ents…

Now, I’m going to use the Modify Reconstruction Pole P tool to describe their changing positions at various times over the next hundred million years. For convenience, I’ll copy the last position Euler coordinates to the 150.0 time row each time I make a modification.

Now that we’ve described the slow travels of our friends the slow-moving tree-people across continent 100, we now do the same thing for continent 100 itself.

Now, if we run the animation, we’ll see that the movements of our three little friends follow the continent as it moves. To make that clearer, try adding a third point that remains stationary until the last minute. Let’s call this stay-at-home ent, Taylor. I’ll have Taylor remain stationary until 125.0, Then I’ll have it meet up with some of the other points at 150.0. As you see, although there are no moves described for plate 104 until time 125.0, the point follows the movements of the continent.

It might not be clear that Taylor is truly stationary with respect to plate 100, because the interpolation of plate 100’s movement causes some jiggling. So select the menu item Reconstruction>Specify Anchored Plate ID… and set the PlateID to 100. Now rerun the animation.

I hope this demonstration was helpful.
The Astrographer

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