I've been trying to read up on tectonics and I kind of get the idea... your restatement of the effects clarified a lot. What I really don't understand is WHY they would move against another plate instead of into it, or away from it... like... how does it shift one direction instead of the other?
there's a couple of different ways a lake can form.
If you have a depression in the ground (think of a bowl, or a saucer) and you have a TON of rain in that area, the depression will fill. It has to be a LOT of rain to make this a lake (or even a pond) because most of the water will be absorbed, eventually, into the ground. Because of this, sometimes a lake will form, and if there isn't enough precipitation, it will dry up, because more water will be absorbed than added. (Think of puddles after a heavy shower.. they pool wherever the ground is lowest.)
This will also happen with other sources of water - like rivers - anywhere there is LOWER ground, and more water than can be absorbed/diverted, the water will pool.
So lakes might be more frequent where 2 rivers meet in a low-lying area than a single river, because there's more water now, and more force behind it.
But you also need that depression in the ground
Water flows down, so if there's lower ground than the lake-area, the water is going to leave that way. If there's too *much* lower ground, ALL the water will leave, and you won't have a lake at all. If there isn't *enough* lower ground, the water level will keep rising. The lake will get bigger, and cover more/higher area. Eventually it will find a lower path to take. Water will flow out of the first lower area it finds, which is why USUALLY there's only 1 river leading out of a lake, and almost all lakes have a river leading out.
If a lake does not have a river leading out, either it finds an exit for the water underground, or the water is absorbed and it dries up.
Another way a lake can form is from flooding. This is pretty much the same thing as your "ice melt" lakes. When, say, a river floods, it covers land that isn't usually in its' path. Sometimes it fills depressions in the ground that were dry ground before. As the thin layer of water on the higher ground is absorbed, there's still water in the depression. (think of puddles - the smaller ones disappear first.)
The water in the depression is sometimes absorbed, but some of it evaporates, causing more rainfall, and cycles the water back into the new-formed lake.
There's also water under the ground. (More than most people think). Sometimes, the force of the water pushes it up through the ground, like lava from a volcano. This could evaporate or be absorbed, but usually it turns into springs, or pools into lakes.
Sometimes... there's these certain types of volcanos that EXPLODE ... literally explode... no more volcano. no more anything-that-was-around-the-volcano. just a huge (disturbingly round) pit in the ground. The water outside the "blast radius" is still flowing like it normally would, but now, instead of running over land, it finds this huge hollow and fills it.
Of course all of this is the highly-simplified, not strictly accurate/scientific explanation, but it is, in essence, why lakes *usually* form. There are lots of other ways too, though
I'm sure someone will come along and explain it better, but those are the basics