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.
In other words we are often able to see through the dark side of the moon's body the light on the other side. In this faint light the telescope can distinguish both the larger spots, and also bright shining points, and even when more than half the moon's disc is illuminated, a faint grey. p. 338.