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GotAU?

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  1. Here’s a good free PDF textbook on the fundamentals of geomorphology - Some interesting material, especially the parts about how stream deposits are layered and exposed, how faults expose different layers along hillsides (scarps) and how they fill in, etc. All good stuff for those that want to search: Fundamentals of Geography (free ebook): http://www.ndma.gov.pk/tools/vkc/vkc/Geomorphology/eBooks/1.pdf
  2. Placer deposits are stream or other gravity deposited minerals. You might be down low in a recent streambed working fine gold for example, and miss older stream channels with richer and more coarse placer deposits higher up on the bank if you don’t know what to look for. I was mapping the geology in a canyon a long time ago in field school, and we found a place with out of place rocks that obviously rolled down from a slide up higher in the canyon. It had quartz and pyrite in some of the rocks and one of the students hiked up the side of the canyon to find where it came out of. Pretty low grade gold ore if anything, but it was pretty. Knowing some basics about rocks and geomorphology helps in the search!
  3. Understanding geomorphology helps one to know how and where alluvial deposits (placers!) form, what landforms are most likely to indicate certain types of strata, to recognize faults and to merely know and appreciate a simple landscape that much more. I have references to more academic books on it from college, but a simple google search and a basic book on it would be helpful and interesting for those just learning about it.
  4. Actually, meteorites hit the earth at different speeds, some melt the surrounding rocks and others don’t, and it is attributed to the speed and mass of the object: Meteor crater formed by low velocity impact.https://www.nature.com/articles/434157a http://www.impact-structures.com/impact-rocks-impactites/impact-melt-page-impact-melt-rocks-impact-glasses-and-congeners/
  5. Originally, I commented on how the speed of the earth may affect crater size, depending on the vectors of the collision, but I was misunderstood. I was talking about the orbital velocity of the earth which is over 100,000 km/h, not the spin of the Earth, which is much slower.
  6. Its old also, and was in sand. Perhaps the desert wind and sand covered it. What I meant is that if a meteorite hits in the same direction Earth is orbiting, vs opposite of it, then the speed will be much different. Also the composition of the country rock and the meteor would have an affect, along with the age of the impact. But then, there’s always the alien effect variable... ;)
  7. Impact velocity, entry and orbital vectors of both Earth and the meteorite, all that stuff?
  8. He must be using the density of heavy water? ;)
  9. He must be using the density of a mixture of heavy water... ;)
  10. I would also start with this mineralogy website next: http://isgs.illinois.edu/outreach/geology-resources/using-characteristics-minerals-identify-them
  11. The road heading north from Hinckley to the base of Opal Mountain is doable with 2wd and good clearance, but the road up to the summit of Opal Mountain is steep and narrow and has lose rock, you’ be better off hiking it if you don’t have a short 4wd like a jeep with good tires. Also, Black Canyon is the best way to get to Scout Cove if you don’t want to rough it going the four-wheel-drive route over the ridge from Opal Mtn. It’s a really cool place, you should check it out either way!
  12. I guess I’m going to have to get a better pick! It’s still a pretty fun place to collect agate there, we got a few nice ones. Also went out to the nearby dry lake bed to look for meteorites, but a lot of it was actually filled with water!
  13. The article said there were at least 26 craters there.
  14. Thanks for your reply. I have found a tiny piece of fire opal in Cadiz Valley before, but it may have been a flake from point napping (probably a Native American “manuport”) as there were no others found in the area. Wish I knew where their source was, but their trading could have covered over hundreds of miles.
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