FOR THOSE WHO LIKE TO ROCK

Think of a rock. It’s angular, grey and on the ground, right? Wrong. Rocks come in a staggering variety of shapes and colours, which help us decipher the stories of their geological lives. Here are just a few of the fantastic rock formations found on this planet…

- MIKA MCKINNON

BALANCING ACT

AH-SHI-SLE-PAH WILDERNESS, NEW MEXICO, USA

“The Ah-Shi-Sle-Pah Wilderness can feel like an alien planet, with its strange shapes, colours and lack of vegetation,” says Stan Allison, of the Bureau of Land Management Farmington Field Office. The hoodoos – irregular columns of rock – dotted around the landscape also help create that otherworldly quality.

Hoodoos are a lesson in differential erosion: the stronger sandstone resists the erosion that acts on the softer surrounding rock to create spires and precariously balanced capstones. Elsewhere, the ground is so soft that rain cuts vertical sinkholes into hills, carving mazes of ravines and gullies.

The Ah-Shi-Sle-Pah Wilderness is also home to fossilised turtles and crocodiles – a lurking reminder that the parched desert was a humid swamp only 75 million years ago.

BED OF NAILS

TSINGY DE BEMARAHA NATIONAL PARK, MADAGASCAR

This vast field of rocky spires is the spectacular remains of a lagoon from the age of the dinosaurs. The clints and grykes (patches of limestone pavement separated by cracks) are enhanced by a subterranean labyrinth of caves that collapse and deepen the grykes.

The structure began to form 200 million years ago when calcium carbonate built up on the bottom of the lagoon. It was compacted into limestone before being exposed by tectonic uplift and falling sea levels. In the millennia since then, monsoons carved out the soft rock while acidic rain etched scalloped edges along the jagged needles.