Time expressed in years before present day.
~2,000,000,000: Paleoproterozoic era, possibly during the Orosirian Period. Sediments are laid down in a shallow sea teeming with the newly evolved Cyanophyta, or blue-green algae.
~1,700,000,000: Probably during the Stratherian period, after the evolution of multicellular life, intense heat and pressure cook the above sediments into metamorphic rock, the Vishnu Schist. Intrusions of volcanic rock, the Zoroaster Granite, occur at about this time.
~1,200,000,000: During the Stenian period, as the supercontinent Rodinia is assembling, a layer of dolomite sediments out atop the Vishnu schist and Zoroaster granite. This will be called the Bass Limestone. After a relatively brief period of time, perhaps only a few million years, the sea from which the Bass Limestone was deposited recedes, and river deltas along the advancing shore lay down mud, silt, and sand that will become the Hakatai shale. These wetlands are home to stromatolites, large reef-like structures made by colonial cyanobacteria. The Hakatai emerges above sea level, is eroded away in part along with any overlying layers, and then re-submerged, after which sands are deposited —these will become the Shinumo Quartzite — and then tidal flat sediments upon the sands, which become the Dox Formation.
~1,100,000,000: A series of volcanic eruptions cover the area in basalt up to 1,000 feet thick. This will be called the Cardenas Basalt.
~1,050,000,000: After the Cardenas Basalt (and the rocks below it) is uplifted and eroded, shallow marine sand accumulates in some places: the Nankoweap Formation.
~1,000,000,000: For the next 175 million years, the sea advances and retreats. As it does so, it lays down alternating layers of coarse (delta or near-shore) sediments, and finer (deeper-water) sediments. These become, in order of decreasing age, the Galeros, Kwagunt, and Sixtymile formations.
~800,000,000: Tectonic faulting activity breaks up the landscape, creating fault-block mountain ranges and tilting all the strata from the Bass Limestone to the Sixtymile Formation to about 15 degrees from the horizontal. A hundred million years or more of erosion commences, in most places removing all trace of the Nankoweap through Sixtymile formations, in some places scraping the earth clean down to the Vishnu Schist.
~550,000,000: The region is once again slowly submerged in ocean water. This ocean water now has multicellular animals living in it, some of them, such as trilobites, brachiopods, and crinoids, with hard shells. As the shore advances over the landscape the Tapeats Sandstone is laid down, consisting of coarse beach sand and conglomerated cobbles.
~530,000,000: Shallow seas deposit silt, which will become the Bright Angel Shale.
~516,000,000: The sea is deeper now, and deep-water calcium carbonate precipitate accumulates on the sea floor, which will fuse into the Muav Limestone. For more than 150 million years afterward, any sediment laid down on top of the Muav Limestone will be eroded away — if any is in fact laid down, which we do not know.
~350,000,000: Water erodes channels in the top of the Muav Limestone, and this water is rich in calcium, likely from dissolving the Muav. Some of that calcium is left behind as precipitate. It forms the Temple Butte Limestone.
~330,000,000: The area is now near the equator. A shallow tropical sea teeming with Devonian animals and aquatic plants covers the land. Thick layers of limestone and dolomite are deposited on the floor of this sea, entombing and fossilizing many of its inhabitants. This will become the Redwall Formation.
~325,000,000: Tidal estuaries deposit mud and silt, which becomes the Surprise Canyon Shale. This rock is friable, and all but a very small amount of it is eroded away over the next fifty million years.
~285,000,000: Shallow estuaries and tidal flats cover the land. The sediments laid down in them become shales, siltstones, and limestones. Some of the layers — collectively known as the Supai Group — contain fossils of early amphibians and reptiles.
~265,000,000: After another dry period in which rock layers are eroded, the water returns: riparian wetlands in a generally arid climate deposit a torte of mud, silt, and rust in many thin layers. This will become the Hermit Shale.
~260,000,000: Chronic drought hits the area, and the landscape becomes a desert of pure quartz sand, which becomes the 600-foot-thick Coconino Sandstone.
~251,700,000: In an event perhaps related to the chronic drought, almost all life on Earth dies.
~250,000,000: Surprise! The sea comes back, comparatively devoid of living things. As it advances and recedes, occasionally leaving behind chemical-rich lagoons of water to dry out and leave their dissolved salts behind, layers of sand and calcinated silt and gypsum are deposited atop the Coconino sands to become the Toroweap Formation. Starting at about this time, braided coastal rivers deposit thick layers of silt and sand, the Moenkopi Formation, all of which will then be eroded away — at least in the area we’re discussing.
~225,000,000: Another sea, or series of seas. These deposit calcium carbonate, which will become the Kaibab Limestone, some of the youngest rock in the area. But not the very youngest.
~75,000,000: After being walked all over by dinosaurs for 155 million years, the land begins to rise up. It is the start of the Laramide Orogeny, which may or may not have anything to do with the Farallon Plate subducting under the North American Plate at the latter plate’s western edge, which is now along North America’s west coast, in Utah. For whatever reason, the whole countryside starts to lift up into the air.
~35,000,000: Another pulse of uplift. Watercourses in the area respond by digging deeper.
~5,300,000: Geologists will disagree in the early 21st century as to what happens now. Some will say that the Hualapai drainage system, digging ever deeper and eastward into the Kaibab Plateau, breaks through into the drainage system of the Ancestral Colorado, which until now had flowed southeastward into a lake basin. The opening up of the Gulf of California by the San Andreas Fault likely plays a role, as the Hualapai had also formerly drained into a lake basin. The lowering of the watershed’s bottom end to sea level greatly increases the cutting power of the river. Other geologists will maintain that stream capture alone could not produce the landscape of the 21st Century, and that the lake the Ancestral Colorado fed probably overflows into the Hualapai’s drainage. Either way, a catastrophic flood takes place, and the carving of the Grand Canyon begins in earnest.
~3,000,000: The climate gets wetter during the Pleistocene, and more water cuts the Canyon more deeply.
~1,800,000: Volcanoes erupt, forming the youngest rock in the Grand Canyon. The eruptions dam the river at least a dozen times over the next 1.4 million years, causing gigantic reservoirs to form. Some of the lava dams are 1,000 feet high, with the full force of the Colorado flowing over them in impossibly huge waterfalls as it cuts troughs through them. The Canyon reaches nearly its current depth about now.
~10,500: There are definitely people passing through here by now. How long they’ve been doing so we don’t know.
~4,000: There are definitely people living here year ‘round by now.
~1,200: The Ancestral Puebloan people build remarkable and sturdy edifices in the area.
138: John Wesley Powell rafts the Colorado through the Canyon singlehanded.
113: Much land around the Grand Canyon is declared a preserve by President Benjamin Harrison.
99: Grand Canyon National Monument is established by Theodore Roosevelt.
88: Grand Canyon National Park is signed into existence by Woodrow Wilson.
40: My friend Dave prevents the building of two dams within the Canyon.
6: President George W. Bush, an avowed fundamentalist Christian and smirking denier of scientific fact, is sworn into office.
3: The National Park Service approves the gift-shop sale of a book claiming the Canyon is just 6,010 years old while denying other new books shelf space. Park Service brass stonewalls in defense of the decision, despite sharp criticism from the non-ignorant community, until the present day.
2: I trace the delicate outline of a crinoid stem in a block of Redwall Limestone that has fallen a few hundred feet from its place of origin, far above the trail. It exists, for now, until the wind and water break it and it runs out to the fetid water of Lake Mead to add its silt to the reservoir. A million of its compatriots are still encased in the rock above. I look for the mold, the negative impression of the stem where the rock has split, and find it. The texture of the living crinoid is pressed into the rock, a Devonian cuneiform, and a far more hallowed scripture than any ever written by the hand of humans.