Why do mountains have a triangular shape? How much rain must fall to start a river? How does one grain of sand become an entire dune? Join National Geographic as we show you how the Dynamos of Destruction sculpt our Amazing Planet. But hold on tight, because this is no ordinary view. Our time machine will sling shot you back to the formation of Earth's first continent, then propel you through billions of years of geologic evolution to see the Earth as we know it today. A little dizzy? That's just the beginning. We will release you in raging rapids, twirl you in whirling winds and drop you from the tops of gigantic glaciers. Watch in dazzling HD how the Earth starts to erode, from water, wind, and ice, to sculpt our Amazing Planet.