How did the Grand Canyon get so deep? What are the secrets revealed in its mile-high walls, and what makes a world-class white-water rapid? Will Gadd climbs a sheer 400-foot pinnacle to see what the birth of the Grand Canyon looked like 70 million years ago. He reveals the hidden worlds buried in the layers of rock in the canyon's walls. From deserts to oceans to tropical forests, it's all there as you go down. When he reaches the bottom, one mile down, he goes white-water kayaking down the canyon's interior to see exactly how those famous rapids are made. And just beneath the waterline he reaches the bottom of the Grand Canyon. He discovers America's basement, a layer of dense black rock that the United States is built on. This is the story of lost mountains, epic adventurers and gigantic volcanoes that have shaped one of the most iconic natural wonders in the world. In the biggest, most dangerous stunt of the series, Gadd flies across the Grand Canyon using just the power of the massive thermal lift generated by the intense temperatures formed deep within the canyon.

How can the biggest living thing on the planet survive almost anything? How did it get to be so big? And who really is the biggest killer on the reef? Working with geologists and marine biologists, extreme adventurer Will Gadd gets up close and personal with the largest living thing on the planet (the only one you can see from space) — the Great Barrier Reef. The story of what makes this place the perfect location for the largest reef in the world takes Gadd far inland in search of clues to Australia’s mysterious past. This is the hidden story of a world that has died and been resurrected many times and it takes Gadd on an incredible voyage above and beneath the waves of Australia’s eastern seaboard. It has long been known that the remains of a much older reef are buried beneath today's Great Barrier. But just how old is it? The mission: to get a piece. Scuba diving to depths of 190 feet, the team retrieved a rare piece of that ancient reef. This was a first — scientists can now date that forgotten ancestor to 12,000 years old.

What forces created Earth? What do the Grand Canyon, the world's tallest waterfall and the Sahara have in common? What is a hot spot and how did it make Hawaii and the Great Barrier Reef? And what does it really take to move a mountain? The world's great natural wonders are works in progress. Getting up close and personal with them gives adventurer Will Gadd and scientists from around the world unique insights into the colossal forces that created the whole planet. This is big geology and Gadd's unique skills make him best suited to reach the rocks science needs in order to tell this epic story. Written in the folds of the northern lights above Alaska, a clue to the formation of the planet is uncovered. On the island of Hawaii, Gadd sees the processes that created the continents and in the Grand Canyon he experiences the power of water. In Australia’s Great Barrier Reef, he discovers how continents move and how erosion created the perfect stage for the world’s tallest waterfall.

Where would you find the biggest dinosaur ever? The oldest glass in the world? A cave so precious it changed history? In the same place where you can fly forever, ski at 58 degrees Celsius (136 degrees Fahrenheit) and drink million-year-old water. The Sahara Desert provides unique challenges. Rock climbing in the extreme heat with geologist Matt Genge, Will Gadd discovers the ancient history of a lost superdesert. While Matt Genge and palaeontologist Matt Lamanna explore the eastern side of the Sahara, Gadd's journey takes him south, deep into the western side. Between them, they discover a world of deserts, savannas and oceans, and Gadd uses the extreme heat to try and reach the Holy Grail of paragliding — never-ending lift. He finds a new way to cross the oceans of sand and discovers what happened to the lost waters that once made this ultradry world a lush, beautiful land. The program offers an exclusive view of 12,000-year-old cave paintings previously seen by only handful of people in the world. We uncover previously unseen evidence of a massive meteorite strike. It is now estimated that the rock that slammed into the Sahara was half a mile wide.

What makes Alaska the last great wilderness on earth? Why is it the best place to see the northern lights, and why are the mountains full of sea creatures?

How does a mountain shape the perfect surfing wave? What creates a paradise — yet also destroys it? And how could an island wipe out a metropolis an ocean away? To get at the truth behind these questions, Will Gadd takes to the air in his paraglider for a unique perspective on paradise. But climbing a 40-foot waterfall, diving in a mysterious undersea tunnel and mountain biking through 10 of the world's 13 climate zones on one mountain isn't enough. With the help of geologist Lloyd French, Gadd is able to discover the astonishing natural forces at work just below the surface. Using the skills of super-surfer Kaleo Amadeo, Gadd finds out what processes turned this tiny patch of real estate into the greatest surfing paradise on earth. Diving beneath the waters of the Pacific, Gadd discovers how the islands are formed. In an epic sea kayaking adventure, Gadd uncovers new evidence showing the processes that created one of the islands. This leads to a compelling insight into the death of the islands and the very real dangers this could hold for cities as far away as Los Angeles.