From the park's website
Picture it: Payson, 1.73 billion years B.C., when there was truly ocean front property in Arizona. The adjoining seas were spawning first life of amoebas and algae, and explosive volcanoes dominated the coast, dispensing thick, viscous flows of red rhyolite that billowed great clouds of steam as the lava encountered water. Stream systems wore down the mountain ranges, dropping off rounded remnants of the formerly towering rocks along the way, intermixed with coarse grains of sand, only to be baked as another flow of lava coated the sediments. Earthquakes would periodically rock the region as the adjacent oceanic plate was shoved underneath the continent, feeding the volcanic frenzy. This went on for roughly 80 million years, until the rock record pulls us up short at what geologists call The Great Unconformity, 1.2 billion years of missing time, almost a quarter of Earth’s amazing history, gone, wiped from the region forever.
Fast forward to roughly 545 million years ago, when the rock record picks back up, telling us that the restless seas spent the next 20 million years encroaching on, and covering, the former beachfront property. The seas filled in the lowlands and eroded away the cliffs, leaving naught but sand, cobbles, the occasional ripple mark, and another unconformity (spanning about 100 million years).
Little is known about this timeframe; however, the overlying rock units (and those in other parts of the Southwest indicate that this was probably a time of great inactivity—very little shaking and baking going on. Eventually, though, the ocean reclaimed its dominance, returning with a vengeance again and again, depositing layers of limestone and shale, and preserving examples of sea creatures such as coral and scallops. Fish were present by now, quite different than today’s fish, which, had humans been present, would have given the unwary snorkeler quite a surprise with their massive, monstrous bony heads.
About 330 million years ago, the seas settled down to some steady work, allowing crystals of lime to steadily accumulate and sea life to flourish. Sea snails and clams arrived on the scene, trawling the shallow marine floor for sustenance, while corals built up a reef offshore. Just to the north of this area, the winds were busy carving out a landscape of sand dunes that were dissected by the occasional river, supplying the ocean with fresh water and sediment.
But then, something happened rather abruptly here. By about 290 million years ago, all record of geologic activity vanished yet again. What happened in Payson? Why are rock units to the north and west present to attest to what happened for the next 225 million years, but not here? Were they eroded away? Or were they even deposited in the first place? A giant supercontinent, known as Pangaea, formed and broke up, and dinosaurs roamed the planet until extinction, but no record of any of those monumental events was left behind here for us to interpret.
We can infer from other parts of the western US that volcanic activity increased, as did the number of earthquakes, when the great collision known as the Laramide Orogeny occurred 50- 70 million years ago. This series of events kickstarted the formation of the Rocky Mountains, a time of repeated grinding, crunching, and warping as two tectonic plates collided, causing rocks to break and slide over and under each other.
The next exciting phase for this area didn’t start to occur until probably about 35 million years ago when another mountain building event started up—explosive volcanoes revisited the state, and great blobs of molten rock worked their way from deep within the bowels of earth ever closer to the surface, forming giant granite plutons. This was a different type of mountain building than that which created the Rockies, however. This time, the continent was trying to pull itself apart, extending its