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 our Amazing Planet is sculpted. 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, and then propel you through billions of years of geologic evolution to see the Earth as we know it today. We will release you in raging rapids, twirl you in whirling winds and drop you from the tops of gigantic glaciers. Watch in dazzling high definition how water, wind, and ice erode the earth to sculpt our Amazing Planet.