Tear the Earth Asunder ritual question


So I am in love with the concept of basically being able to create a vast realm in the middle of the Atlantic Ocean using ritual magic to create something out of nothing. Thanks to Transforming Mythic Europe, and the amount of indepth options and explanations on why the math is the way it is, I understand most features of such a thing.

I basic idea is that the magi would first create a central volcanic growth in the middle using a spell similar to Tear the Earth Asunder. Then once that is done they would then create a perimeter circular wall using the spells in Transforming ME before filling in the middle using the filling spells. I am working on the logistical aspects, mostly cause its very fun to do.

The basic question though is I am not sure about the logical optimization and other elements of the spell Tear the Earth Asunder in Hermetic Projects, page 13. The spell doesn't explain things like the spells in Transforming ME does so I don't understand fully the math behind the levels.

Hear are some questions
-If the ritual is activated on the bottom of the ocean would the 15,000 feet high peak be from ground level all the way up?
-The notes say the mountain is about 20 miles in diameter, though the crater is a fraction of this size, how much would the crater be?
-Once cast and the volcano erupts once is it still considered an active volcano or does it become dormant / dead after its single activation.

Okay, now here are my wishes, though I am not sure how to modify the spell to make it the way I would like.
-I want the caldera itself to be 30 miles, which looking up the info in online sources is actually a possible size.
-If the center top caldera is 30 miles then how much larger would the rest of the sloping mountain peak be?

Basically, the whole +13 Sizes thing that is in the spell, how does that translate into 20 miles in diameter and 15,000 feet high.

So help on this would be quite appreciated, especially if its by those with better understanding of the math that lies at the core of the system.


PS. The whole thing is a center 30 mile diameter caldera which will have a city carved within, then a rough 100 mile diameter valley (with the caldera mountain counted as part of that), then a 25 mile thick mountainous peremeter all around the valley, with a final couple of paces wide magically impenetrable 'wall' on the outskirts. The interior would have plains, forests, hills, two lakes, etc. A single area in the very front would be carved away enabling boat traffic into the realm from the outside ocean. This just gives some general descriptions, I already have maps, hehe. :slight_smile:

The math is actually pretty easy. The basic individual size for a stone is 1 cubic pace, or about 1 cubic meter and each extra size increases the volume by 10. So you just pick the appropriate shape, in this case either a cylinder or possibly a cone, and calculate the volume. Using a cylinder (with V=pir^2h) you'll need roughly 410^12 cubic meters of stone for the example spell which will translate into increasing the size by 13 magnitudes. For your spell with a 30 mile diameter (and still assuming 15000 feet and a cylinder shape) you will need about 910^12 cubic meters of stone so size +13 will still be enough.

Whatever you have planned for the surface it won't really make a difference for the final size.