The Grand Canyon in Arizona is one of the most jaw-dropping holes on Earth - 446 kilometres long, 29 wide in places, and nearly 2 kilometres deep. The Colorado River chiselled it out by scraping bit by bit through layers of stone over the last 5 to 6 million years.
The canyon’s walls are a giant ladder back in time. The rocks at the rim are about 250 million years old. As you climb down toward the river, every layer gets older. By the time you reach the Colorado at the bottom, you’re touching dark rock that formed 1.8 billion years ago.
That’s almost half the age of the planet, from a time when life was nothing but microscopic bacteria. The canyon also has its own weather: it’s often cool and snowy on the rim while baking at over 40°C on the river below.
