Buried Canyon EarthCache
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A review of the lava flow that took place.
Logging Tasks
1-What similarities/differences do you see from the hills to the Northeast to the plateaus to the Southeast.
2-If you look up the hill NE you will see some basaltic columns just under the top, and in the middle of the hill. What are the differences in them? Do you think it took the same amount of time for them to form, and why?
3-There are stones periods in the Plateau (not counting the capstone); Upper Red, Shnabkaib, and Middle Red, which one do you think is the hardest and why?
Volcanos and the Virgin River
About 100,000 years ago there was a volcano north of here, it is currently listed as Cinder Hill on the maps. The lava flow from this volcano moved off the plateau and flowed down and into the Virgin River Valley. It then flowed into the valley over a stretch 4-5 miles long, and filling the virgin river valley to a depth of about 400 feet.
Lake Formation and draining.
You are currently at the downstream end of the flow, where the upstream end is at the ghostown of Grafton about 4-5 miles up river.
Because of the blockage the river backed up and formed a lake into Zions park. There have been a number of small to large lakes that have formed from landslides and volcanic activity. The river then began to erode around the south end of the lava flow, and the lake eventually drained.
Eventually the virgin river eroded down the channel into what we see now. It worked its way around the South, eroding the softer sandstone and mudstone that makes up the plateaus and their bases. The basalt rock that makes up the lava plug in the gorge is far harder and did not wear very much, making that slope very steep.
Basalt
The NW hillside is made up of the basalt plug. Some of it is columnar. Columnar basalt is created in the cooling process. When cooled the basalt shrinks in size. It cannot shrink in two directions (vertical and horizontal) without one of the directions cracking. Normally these fracture Horizontally. While the vertical shrinking just shortens the columns. Heat and slow movement may deform those columns later on. Columns that cool at different rates form different sized columns. Slow cooling making larger columns We have a few different flows here. Some on top of others.
Sandstone Plateau
The plateau to the SW is part of the Moenkopi formation. It is made up of tidal and ocean deposits, and some floodplain deposits. From a period of 200-250 million years ago. The top of the plateau is a harder conglomerate cap, that slows the erosion of the top, and leaving steep sides. The plateau here is made up of three members (not counting the hard conglomerate cap). Upper Red, Shinabkaib, and Middle Red. Softer stone will wear faster and so will be steeper.
Upper Red (near the top): Generally thin, fine grained, roughly stratified, shale-like sandstones and mudstones, light red, chocolate-brown; quartz grains cemented by lime and iron; some gypsum and limestone; many beds ripple marked..
Shnabkaib member (in the middle of the plateau), White, pink, light red, sandy, gypsiferous, friable shale and foliated gypsum, forms a rugged slope, brightly color banded.
Middle red member (near the bottom). Light red and yellow brown, shaly sandstones; dominantly fine, even quartz grains; some gypsum; generally thin, irregular bedding.
Additional Hints
(No hints available.)