Laying The Surface
So now our magma has cooled some. Rather than being a giant ball of swirling hot liquid rock, a crust of sorts has formed around the globe. This crust floats along on the mantle, just like a collection of paper boats might on top of a gathering of bubbles in a sink full of water. However, to continue this metaphor requires that the boats be densely packed in a limited space. The boats bump and grind against one another as the water currents change, causing the bubbles and suds to move as well. If our boats are all different shapes and sizes as things tend to be in nature, then one boat might be able to push another one down or up a bit.
The poll on how many plates came out to a tie, so it averages out to fourteen. Since the Earth has "around a dozen," this makes our fictional planet quite similar to the one we live on now. The materials in the plates has a lot to do with the scenery as it forms.
The Highs And The Lows
There are two basic types of materials that can form a plate. Dense, heavy rock such as the type of material you find on and around volcanoes (basalt) forms the plates that make up our ocean floors. Just as a heavily laden boat will float lower in the water than an empty boat of the same type, this type of rock lays low in the mantle. The other type of rock forming our planet's underlying structure consists of quartz and a family of minerals called feldspar that all contain aluminum in some form. Plates made of this material (up to sixty-two miles thick) are far thicker than the basaltic plates (three miles thick), and yet they weigh roughly the same. So, the mix of lighter and heavier plates will determine how high the highs on your land goes, and how low the lows go. Dump water onto the result and suddenly you have oceans and continents.
This issue brings me to the subject of the poll from Oct 6 to 12. We need to decide how much precipitation falls on this planet of ours. This will determine how much of our world is buried underwater, and how much of it is sticking out to provide land for the people we will eventually put on it. There are of course possibilities for writers who don't want to deal with water-based planets at all. However, since I'm trying to make this project as it progresses have a nice broad appeal, it wouldn't be too helpful for those trying to write in our world to have something that is so alien.
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