I place my left hand against the slab of grayish-black, water-polished rock. It is 3:46 PM Mountain Standard Time on March 20, 2025, and I’m somewhere deep in the Grand Canyon. The rock beneath my hand belongs to the Granite Gorge Metamorphic Suite, which sounds like the title of an orchestral piece by Ferde Grofé, rather than a series of geological strata roughly 1.75 billion years old, give or take a few million years.