The rock on which you’re status is a composite of quartz, feldspar, biotite, and amphibole. It shaped greater than three-and-a-half billion years in the past when molten subject material cooled to shape granite deep within the abdominal of the Earth.* Later, this granite used to be stuck within the vice of plate tectonics, re-melting it in order that red feldspar may wind its means into the material. Steadily it hardened handiest to warmth up once more, including nonetheless extra colours to the swirl. This used to be about 800 million years in the past (Ma). Then, about 100 Ma, it used to be rudely squeezed to the skin. The dinosaurs proliferated, the dinosaurs died. Newly assured mammals pawed on the rock. Then, ice. Glaciers flowed from side to side at periods around the long run northern states, overlaying the gneiss in a thick glacial until. In any case, about 12,000 years in the past, Lake Agassiz burst, unleashing a large bulldozer referred to as the Glacial River Warren. This reduce a deep gorge via what’s now the Minnesota River Valley, taking out the until apron, exposing the gneiss, and making the ones damned potholes.
[* Individual zircon crystals from the gneiss have been dated to 3,524 ± 9 Ma. This makes it not only the oldest intact surface rock in the United States, but one of the oldest rocks on the planet. The oldest intact surface rocks on the planet are closer to 3.8 billion years old, although some have claimed older ages for rocks (e.g.) in the Canadian Shield.]