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.
Above: One of Galileo s first sketches of the surface of the Moon. Image Credit: Octavo Corp./Warnock Library). Before Galileo s observations the Moon was thought to be a perfect, smooth sphere (the light and dark regions that can easily been seen by eye were unexplained blemishes on a smooth surface). The perfection of the heavens set the planets apart from the imperfect Earth.