The following is a transcript of the narration for this panorama location. To watch and listen to the narrated panorama, enter the project here at this location and then press the play button.
We have now descended the South Kaibab Trail to deep within the inner canyon, almost all the way down to the Colorado River. Look back up and there is no sign of the Tonto Platform at all – it is completely hidden behind the cliffs of Tapeats Sandstone that form its rim. Nearly all of the upper canyon is gone as well – we only see the tops of Zoroaster Temple, Sumner Butte, and Bradley Point across the river from us, and just a bit of the end of Dana Butte visible downstream.
We are very near the junction of the South Kaibab and River trails, just one short switchback down from our spot here on the South Kaibab Trail. We can see a bit of the River Trail heading off downstream, just beyond and below the hiker that has paused to enjoy the scene.
All around us here is the ancient bedrock of the Grand Canyon, the dark black, shiny Vishnu Schist, with swirls of pink Zoroaster Granite embedded within it. To learn the story of the Vishnu Schist and Zoroaster Granite, we have to go back in time even before the supercontinent Rodinia, discussed in the previous narration, had formed. Nearly 2 billion years ago, geologists believe, the area that is the Grand Canyon today was part of a string of volcanic islands in the middle of a vast sea. Seabed dove underneath it in a plate tectonic subduction zone, where it melted and bubbled back up to the surface and created the string of volcanos, much like we see in the Aleutian Islands today. Many generations of volcanoes piled up tens of thousands of feet of layers of lava, ash, sand and mud. Eventually , about 1.7 billion years ago, the sea closed and another continent smashed into the island chain, heating and metamorphosing the mix of lava, ash, sand, and mud into the Vishnu Schist. Pools of magma that had fed the volcanoes, but still remained within the Vishnu rocks, eventually cooled and crystallized into the swirls of Zoroaster Granite.
Directly across the river from us is the mouth of Bright Angel Creek, and its delta formed from the detritus of countless flash floods that have roared down Bright Angel Canyon over the centuries. Three major flash floods have roared down Bright Angel Creek within the last hundred years, in 1936, 1966, and 1995, and inevitably there will be more.
But this day is a tranquil, and the members of the rafting party beached just above the delta need not worry about a flood. They may have headed just around the corner to the canteen at Phantom Ranch for some lemonade or a beer, or maybe they were more ambitious, heading up the North Kaibab Trail on the fine 12 mile round trip to visit Ribbon Falls. They floated underneath the Black Bridge just before landing, and we can see the bridge’s concrete piers embedded within the bedrock on the south side of the bridge, anchoring the suspension cables that hold up the bridge. We can also see the entrance to the hundred yard long tunnel that hikers pass through to reach it.
From here we can head downstream along the River Trail, twisting through the Vishnu Schist towards the Silver Bridge, but pausing first at a nice viewpoint directly across from the mouth of Bright Angel Creek.
Heading up the South Kaibab Trail, we will climb a few switchbacks up through the Vishnu to a fine viewpoint that tells the story of the destruction of a supercontinent. Heading down the trail, we’ll reach the Black Bridge approach tunnel, pass though it, and cross over the bridge to a spot right underneath it, on the bank on the far side of the Colorado River.
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