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.
Umbra and penumbra when referred to the moon describes the shadow which is formed when light is blocked from the sun, by the moon. This shadow which falls on the Earth and haâ¦s two distinct regions; a partially shadowed area which is the penumbra and the centre point a totally dark umbra.