Onyx River
The headwaters of the Onyx River are near the ocean and the river flows away from the ocean. This rather unusual behavior is a result of how the Dry Valleys were formed. At one time the Ross Ice shelf was thousands of feet thicker than it is today and the ice flowed off from it towards the Polar Plateau, carving the Dry Valleys. Now that Ice Shelf has decreased in size, the ice has retreated from the valleys and the Polar Plateau is higher than the valleys and the current ice shelf (now at sea level). The glaciers now spill off the Polar Plateau in the opposite direction from which the valleys were formed.