In Utah the youngest layer of one park is the oldest of the next
The roof of the Grand Canyon is Zion's floor, and Zion's roof is Bryce's floor. The parks of southern Utah are not five places: they are consecutive cuts through the same stack of layers.
The national parks of southern Utah are almost always visited as a list: Zion, Bryce, Capitol Reef, Arches, Canyonlands. Five stops on a road trip, each with its recognisable shape and its car park. The list works, but it hides the best part.
Because they are not five different places. They are cuts through the same stack of sedimentary rocks, and those cuts are in order. What ends in one park begins in the next, with a precision that looks arranged.
01 A staircase somebody saw in 1870
It is worth starting with the state's scale, because it explains the rest. Utah covers 219,887 square kilometres and brings together three distinct geological regions: the Rocky Mountains to the north and north-east, the Great Basin in the western half, and the Colorado Plateau to the south and south-east. Everything in this article happens in the third.
In the 1870s, the geologist Clarence Dutton described that corner as an enormous stairway ascending from the bottom of the Grand Canyon to the high country of southern Utah. He gave it a name: the Grand Staircase. It was not a loose metaphor: it was a stratigraphic description.
The sequence runs from the Grand Canyon, in Arizona, northwards, through Zion and the Grand Staircase-Escalante National Monument, up to Bryce Canyon. Each stretch exposes a part of the stack, and the key is that none of them repeats.
02 The limestone that closes one park and opens the next
Here is the fact that orders everything else. Going down into the Grand Canyon, the youngest layer of all — the top one, the first you walk on — is the Kaibab limestone, around 240 million years old. Below it lie fifteen hundred metres of older layers.
That same Kaibab limestone is the oldest formation exposed in Zion National Park, some two hundred kilometres to the north. In other words: the roof of the Grand Canyon is the floor of Zion. Where one ends, the other begins.
The practical consequence is curious: if you visit both parks, you have seen a continuous column of rock more than two kilometres thick, even though you have never stood anywhere it is all visible at once.
03 And again, one step higher
What is notable is that the mechanism repeats. The youngest formation visible in the Zion area is the Dakota sandstone, and that sandstone is the oldest formation exposed at Bryce Canyon.
Bryce, moreover, keeps climbing: it exposes Cenozoic rocks, some hundred million years younger than Zion's. Its characteristic formation is called Claron, and it is the one that produces the famous pink cliffs.
So the full staircase reads: the Grand Canyon digs into the oldest layers, Zion starts where the Grand Canyon ends, and Bryce starts where Zion ends. Three parks, three consecutive stretches, with no overlap and no gaps.
04 The steps are named after colours
Geologists named the steps after the colour of their cliffs, and that nomenclature is still the quickest way to orient yourself. From the bottom up, that is, oldest to youngest: Chocolate, Vermilion, White, Gray and Pink.
The Chocolate Cliffs are the lowest step and define much of the Kaibab plateau, on the north rim of the Grand Canyon. The Pink Cliffs, at the top, are Bryce's. Between them there are some two hundred kilometres of horizontal distance and more than a hundred million years of difference.
Each step has the same profile: a cliff that rises and then an almost flat platform running north to the foot of the next cliff. Riser and tread, five times over.
05 Who stood the staircase up
It remains to explain why any of it is visible. Buried horizontal layers form no staircase: they have to be lifted and then cut. Tectonics did the first part and the rivers the second.
The whole block has undergone uplift of between 1,500 and 3,000 metres, a process beginning with the Laramide orogeny, the same mountain-building episode that raised the Rockies. What is striking is that the Colorado Plateau rose almost without deforming: the layers remain practically horizontal.
With the ground raised, the rivers began to cut. That produced the Grand Canyon, the Little Colorado, Glen Canyon, Marble Canyon, Zion Canyon and the canyons of the Green River. Each one is a window opened onto a different stretch of the stack.
The staircase, then, was not built by anyone: it was left exposed. The layers had been stacked one on top of another for hundreds of millions of years; what was needed was to raise them and strip away what was in the way.
06 How to travel it
The first practical consequence is the order of the trip. If you go from the Grand Canyon to Bryce via Zion, you are climbing the staircase and reading the layers from oldest to youngest. The other way round works too, but backwards: at Bryce you start at the end of the book.
The second is that altitude is not a logistical detail: it is the same variable as the stratigraphy. Zion is low and hot; Bryce is high, its rim between 2,400 and 2,700 metres, and cold. The staircase of rock is also a staircase of climate.
And the third is the one that changes the whole trip. If at each stop you ask 'which layer am I looking at and how old is it?', the parks stop being five handsome landscapes and become a single two-hundred-million-year section, split for convenience across five different entrance gates.
