Originally Posted by
waldronate
Weather is caused by uneven heating of the earth by solar radiation. This uneven heating causes air masses to move. The amount of heating of a given area and the change over time are controlled primarily by the axial tilt of the planet, year length, the size of the planet, the rotation speed of the planet, and atmospheric density. The axial tilt and year length determine the seasons and the min/max possible temperature in an area. Differential heating between the equator and polar regions causes flow of air toward and away from the poles. The size and rotation speed of the planet cause that poleward flow to be deflected to the side, causing the spin that shows in large storm systems. Atmospheric density determines the total energy that can be carried by a parcel of air.
Clouds form when water is evaporated from wet areas, rises, and begins to condense in the upper reaches of the atmosphere. Storms (great masses of clouds) occur when a body of (typically warm) moist air encounters a mass of cooler air. Storms generally gain moisture over bodies of water and lose it over land (more quickly over drier land such as desert compared to woodland or jungle). Larger oceans potentially allow larger storms to form but there is an upper limit dictated by atmosphere and world characteristics.
Surface ocean currents broadly follow atmosphere dynamics. Deep ocean currents follow the same sorts of rules as the atmosphere, but with the added factor that salinity has a major impact in addition to heat (saltier water is heavier than less salty water of the same temperature; warmer water is lighter than colder water). The Gulf Stream, for example, arises in part because cold water sinks just north of Iceland, pulling in saltier water from the tropics, which gets colder and sinks, pulling in more water, and so the current flows.
Plate tectonics arises due to differential heating in the mantle from the core of the planet. Hot rock rises and cold rock sinks. The continents are formed of much lighter rock than the mantle rocks and so float around, following the mantle currents. Then continents collide, mountains tend to form in the collision zone (see the Andes and Himalaya for excellent examples). When plates pull apart, oceans form (see the Atlantic ocean and the new ocean forming in the Red Sea / Africa Rift Valley). The hot rock that rises from the mantle tends to take the form of relatively small plumes. These hot spots break through the crust in relatively small areas. The motion of the plate moving over them can be seen from the action of the hot spot on the plate rock (see the Hawaiian island / Emperor seamount chain and the Yellowstone hotspot / Snake River Valley in the US). The mountains pushed up by collisions tend to be near the edges of plates. They start high (Andes / Himalayas) and erode down over time (see the Appalachian and Ural mountains). Alluvial plains are formed from erosion products of mountains (the great plains of the US are formed from debris from the Rocky Mountains and Appalachian mountains with a bunch of gunk scraped off Canada during the last ice ages).
OK, that's enough intro to geography for now. There are lots of great textbooks out there on this subject and many good college class websites. Physical Geography is what you're looking for.
Sorry about the long-winded spewing but sometimes I can't help myself.
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