Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation is also known as the ocean's conveyor belt (which refers to deep ocean density driven ocean basin currents). These currents, called submarine rivers, flow under the surface of the ocean and are hidden from immediate detection.
The light-colored material is in areas of the Moon called the highlands, which represent the earliest crust on the Moon. Impact cratering shattered this crust and often deformed it, pushing some of it into mountain-high impact crater rims or ejecting it across the surface of the Moon.
The amount of light reflected by a surface is called the albedo. For light colored clouds, the albedo is high, and much of the incoming sunlight gets reflected. Water and dark colored rock reflect much less light. Mercury is mostly covered by dark rock, so its albedo is very low. On the other hand, Venus is covered by a thick layer of clouds, so it reflects almost all of the Sunlight that hits it. Because of Venus' high albedo and its proximity to the Earth, it is the brightest object in the night sky after the Sun and the Moon.