Rock Story -- chunk of granite from Little Cottonwood Creek
Where these rocks are found:
This rock came from the stream bed of Little Cottonwood Creek at the Temple Quarry Nature Trail.
What you observe:
1. It looks lwmogeneous ... well mixed. 2. I see white, feldspar crystals. 3. I see glassy, gray, quartz crystals. 4. I see little black crystals. 5. I see sheeted dark crystals of mica. 6. With my hand lens, I see the crystals are interlocking. 7. I cannot imagine that if I left this rock in a container of water, that the water would percolate into the rock. S. The crystals are coarse grained, I can see them witlwut a hand lens. 9. The general color of the rock is quite light-colored ... a light gray. 10. The rock breaks around crystals but every-which-way except where there is a crack, and then it breaks along the crack. 11. It is difficult to crack big chunks off unless there is already a crack to take advantage of 12. It is possible to knick off little chunks with a rock hammer. It appears that that is what happens to the rock as it travels down the stream ... the rock can become "rounded" altlwugh this one is mostly fresh faces because it's been pounded by rock-hammer-wielding teachers. 13. I can remember the relationship of the gray rocks (granite) to the brownish rocks (metamorphic) in the canyon. The gray rocks were under the brownish rocks. 14. I remember lww there was quite a lot of sand residual around some of the granite rocks at the quarry. 15. I remember how the stream bed had rocks of many sizes ... big boulders to cobbles to gravel to sand.
Where the rock is on the rock cycle when you f'md it:
Now it's a chunk of sediment. Recently it was in the process of being transported and slammed and banged along the stream bottom by water in Little Cottonwood Creek. The stream bed was dry when it was taken as a rock sample. Where the rock was on the rock cycle when it was bedrock: This rock was once igneous bedrock in Little Cottonwood Canyon. It is intrusive igneous rock ... meaning it cooled inside, not outside, the earth's crust. It did not make it to the surface. It crystallized slowly in blob in the Earth's crust where it had intruded the brown metamorphic rocks that were here. Back then these rocks were 5 - 10 miles beneath the land surface. That means there has been 5 - 10 miles of material eroded from here since then. Wow. That's a lot of erosion. I wonder where all the stuff went.
Where is the rock heading on the rock cycle:
It's now a chunk of sediment. if it had stayed in the stream bed, it would have been knocked about and smashed against other rocks. if the stream changed its course, the rock might have been stranded and left to weather on the land surface. Eventually it will disintegrate into its component parts: the quartz will become quartz sand (like Sandy, UT). Most of the rest of the rock disintegrates into clays. The little-black-minerals have some iron in them, and this iron may tum sediments red when it is oxidized. if it is not oxidized but is reduced (chemically) the sediments it is a part of will not be turned red ... in general they will be gray. As sediment it will go one of two ways on the rock cycle: .. a) The rock, or the pebbles and sand and clays eroded from it, will get buried by hundreds, probable thousands of feet of sediment. Ground water percolating through it will deposit cement in the voids between the grains. The pressure of the overlying sediments will squeeze out the water from between the clay particles. The mass will become firm and coherent sedimentary bedrock, or, .. (b) The rock, or the pebbles sand and clays eroded from it will be buried for a while, but then will be exposed and eroded again and be reworked as sediment. AND then. .. if it goes the route of (a) sedimentary bedrock. .. it then will have two paths it can take ... .. to become a metamorphic rock, or, .. to be eroded and become sediment. OR ... ifit went the route of (b) sediment... it then will have two paths it can take ... .. to become a sedimentary rock, or, to be eroded again and become sediment again.
Sedimentary Example | Metamorphic Example | Ignous Example