Mountain placement on first map (WIP)

[Wingshaw]

Just keep in mind that continent/continent collisions are actually pretty rare.

This seems like a perfect time to ask why this is the case? A few years ago, I did some intensive study of plate tectonics and orogenesis, and I noticed that, as you say, there are few convergent boundaries on land, but I could never figure out why. Surely, when converging plates cause the closing of an ocean, it also results in terrestrial collisions.

Can anyone shed some light on this for me?

THW

[Chick]

It's primarily because most collisions of plates containing continental crust aren't as direct as India is. When there is an angle, the huge resistance turns them into slip/slide boundary where the plates slide along each other. The San Andreas fault is an example of this.

In order to have a direct collision of continents such as is building the Himalayas, there must be no ability of the continental plates to go anywhere else.

[Deadshade]

This seems like a perfect time to ask why this is the case? A few years ago, I did some intensive study of plate tectonics and orogenesis, and I noticed that, as you say, there are few convergent boundaries on land, but I could never figure out why. Surely, when converging plates cause the closing of an ocean, it also results in terrestrial collisions.

Can anyone shed some light on this for me?

THW

I think that the explanation is simply probabilistic.
The engine of plate tectonics is the convection in the mantle.
The closest analogy to the mantle convection dynamics is that : https://www.youtube.com/watch?v=jUv4Cid3OnE
Now these chaotic up and down movements are constrained by the spherical boundary so that they translate on the surface in horizontal movements.
These latter exhibit however not a steady state nor any regular (f.ex periodic) dynamics - plates stop, reverse , continents break up, combine etc.
Just imagine that a giant molten plume that started to rise 50 millions of years ago breaks to the surface in the middle of N.America - this would cut America in 2 and create a new plate which would start to move in some direction and create new oceans/mountains.

From that follows that for all practical purposes the plate movement on the surface may be considered random (on time scales of several millions of years).
So now to get a frontal collision between 2 plates it is necessary that the velocity vector is in a quite narrow angle range (f.ex 45° +/- 5°) otherwise, as Chick said, the plates would slide and not collide.
Obviously the probability that this happens is 10/360 = 1/36 what is pretty small.
When one further considers that there are more oceans than continents on Earth and that one has to exclude ocean/continent plate collisions because those subduct, the probability is even smaller.