Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Exodus on 07/07/2004 01:40:51
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The first question of the week:
YOU ARE OUT WALKING AND DISCOVER A RED SEDIMENTRY ROCK (E.G. A SANDSTONE) WHAT CAN A RED COLOURED ROCK SUCH AS THIS TELL YOU ABOUT THE EARTH'S CLIMATE WHEN IT WAS LAID DOWN?
AND FOR BONUS MARKS....
IF THIS ROCK CONTAINS SMALL GREEN AREAS, WHAT MIGHT HAVE LED TO THEIR FORMATION?
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Well, it's red, so it must have some iron III oxide (Fe2O3) in it. And for it to have formed the oxide, there must have been some oxygen in the air / soil / sediment at the time...
I've no idea about the green inclusions - are they copper ?
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Thats not bad... the redness is indeed down to the oxidation of iron and actually suggests that the environment was Warm and fairly dry...
The green inclusions are in fact the passage of old roots which have rotted underground and have subsequently caused reducing conditions. This in turn lead to iron reduction which is a charachteristic green colour...
So Overall, a warm dry environment with trees!
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Come on Exodus, where's the next geology question of the week ?
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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I have visited a "early Ordovician red rock" locality a few month ago which is given to be a fresh water sedimentary system under hot climatic conditions. Two days collecting but I found no fossils there (which is not a surprise) but I've seen many sedimentary figures suggesting a shallow environment (ripples-marks) and probable dry periods (polygonal mud-cracks). All the sequence is almost reddish color, but a few layers are bright green. That seems to fit with the reducing condition period hypothesis exposed by Exodus. I'll buy that.
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Kiss, the interesting thing was that there were what appeared to be round nodules of green rather than layers which had been formed by roots burrowing through the sands and producing reducing conditions upon breakdown.
I saw some great ripple marks whilst in the South Western Alps on some finer grained sandstones. One particular bedding plane had a trackway of bird footprints!
I guess the lack off fossils was down to the environmental setting of the time, it could well have been a braided river deposit? or it could have even been an ephemeral lake?
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Honestly, when observing the basis of the sequence, it could be something like a melting glacier (brech+conglomerate) and I agree for the inner lake idea but really, the thickness suggest a long term pool.
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Sounds interesting, where abouts was it?
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I should be able to put a picture in this board. I've done some. See that this afternoon.
The location is Western France (Britanny).
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Pictures will be great. I'm not too knowledgeable about the geology of North Western France i'm afraid, maybe i should look into it, never really thought about it!
So Kiss, are you a geologist?
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Oh no Exodus [:D], I'm just a simple student but I love fossils and geology. I'm not a specialist huh [:I] sorry I'm so dumb superficial in this field. Very difficult disciplines.
Ok I will post some pics to have a look on. Must find how to host them first.
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quote:
Originally posted by Kiss
Oh no Exodus [:D], I'm just a simple student but I love fossils and geology. I'm not a specialist huh [:I] sorry I'm so dumb superficial in this field. Very difficult disciplines.
Ok I will post some pics to have a look on. Must find how to host them first.
don't be so harsh on yourself!!! sounds like you are keen! nice to have another rock lover on here... not many of us... [:(]
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if you want a site to host them then go to
http://www.photobucket.com
its easy and free, then highlight the picture's details and input them in between the insert image code which may be found on the message toolbar!
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fimg.photobucket.com%2Falbums%2Fv173%2Fdickted%2Funtitled1.jpg&hash=745ee7a83561827188376160f63b4682)
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Greatings,
It's my first picture posting. A friend of mine was kind enought
to open a guestfolder in her photopocket account.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fimg.photobucket.com%2Falbums%2Fv222%2FBlueye%2FKate%2Fbrehec1.jpg&hash=fe09df61f6b9c8839197f7e26a82d581)
The best upper red sandstone+shale exposure at Brehec (Western France).
Left is a volcanic dyke (bubble lava), center a 1/4 meter rejection fault.
The light green reducing episode is very well differencied.
Above, there are compact grey shales sequence.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fimg.photobucket.com%2Falbums%2Fv222%2FBlueye%2FKate%2Fbrehec2.jpg&hash=ae12169f96df456b87a02235c9245a9f)
Ripple-marks on the shale (my pic gives scale).
IMHO, the wavelenght of this sedimentation figure should indicate a very shallow water deposit.
A shame, there are no vertebrate foot-print and no vegetation evidence,
because of the early age of these rocks ! The whole succession is azoïc.
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Really nice pics, post any other you get!!!
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I would suggest to you that truly, the red color is indeed from iron (III) oxide, but that the green color would be from one of three possible sources, depending upon the size and orientation of the "mottles" that are present.
The first possibility that leaps to mind is the presence of glauconite, which as a semi- or pseudo- clay mineral, depending upon whether the mineral is ordered or disordered in molecular organization, lends the green color to so-called "greensand" deposits. Glauconite also can be a part of ancient dolomite deposits, such as the Bonne Terre Formation dolomites (Upper Cambrian) we have here in Missouri, USA.
The second possibility may be illite, or an illitic shale deposits, which would be consistent with shallow-water or tidalite deposition.
The final possibility would be coloring due to the presence of bivalent nickel. Nickel (II) sulfide, or millerite, is known to occur as acicular needles in limestones. But what happens when these weather out of formation? The bivalent nickel can become part of any shaly layers or laminae that are present that have any remaining anionic charge. This has also been known to happen in the Cedar Valley Formation (Devonian) of the central United States.
Good question!
Notrenchgeology
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Great picture!
Reminds me of several sequences of siltstones and argillites (St. Regis Fm. and Missoula Group) in the Proterozoic Belt supergroup rocks in Montana and Idaho.
I agree with Notrenchgeology- the red is due to oxidized iron. The green, however, is probably due to reduced iron. My guess, by your comments, is that these rocks may be PreCambrian (lack of fossils). Evidence for alternating oxidizing/reducing conditions is common in Precambrian rocks.
Prediction is difficult, especially the future. -Niels Bohr
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(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi.pbase.com%2Fg4%2F26%2F614026%2F2%2F52321860.thescream.jpg&hash=8c5ceb28d1953c34e17f6bedd346620d)
Here is a photo taken during a recent trip to a famous park- I call it "the scream". The feature is about 15 meters tall and is outdoors.
Identify the type of rock in the photo and how this feature was formed?
Prediction is difficult, especially the future. -Niels Bohr
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I haven't a clue but what a fantatstic picture...and 'the scream' is very apt.....it looks salty !
I presume it's Yellowstone Park eh ?
Men are the same as women.... just inside out !! (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.world-of-smilies.com%2Fhtml%2Fimages%2Fsmilies%2Fparty%2Fballoons.gif&hash=f9f40e7ab655ca9089398c3f3719f593)
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Neil
You hit the hot-spot right on the head, Yellowstone it is.
More later
Prediction is difficult, especially the future. -Niels Bohr
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The photo was snapped at Mammoth Hot Springs near the nothern edge of Yellowstone Park. The rocks are made of travertine, which is deposited from the hot springs. Mammoth Hot Springs has the most abundant deposits of travertine in the park.
In most of Yellowstone, the geysers and hot springs precipitate sinter (or geyserite)- composed of silica which the thermal waters dissolve as they pass through the volcanic material. Silica sinter accumulates slowly- in the order of a few centimeters per century.
Because travertine is calcium carbonate, the thermal waters at Mammoth must pass through older, probably Mississipian-aged, limestones. Travertine accumulates much more rapidly than does silica sinter, in the order of 40 to 70 cm/year- thus the massive formations of travertine at Mammoth. The travertine also dissolves easily, so as the pathways of the thermal waters change, voids often form- which is what I believe created part of the formation in the picture.
As an aside- the thermal springs at Mammoth are not as hot as those found more central to the park- suggesting that they have travelled some distance before bubbling up to the surface. The travertine preceipitates as the water cools at the surface, forming small pools. As these pools grow, the water flows over the edge of the pool where it is shallowest, further cooling the water and leading to more precipitation- in this way the edges of the pools build up.
Prediction is difficult, especially the future. -Niels Bohr
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Plate tectonics predicts that mountains will form at the edge of plates. This seems to hold true for almost all mountain ranges on earth- even those ranges found in continental interiors (Urals, Himalayans, Alps) formed along the edge of a tectonic plate.
Question of the week: THE ROCKY MOUNTAINS (USA) ARE APPROXIMATELY 2000 KILOMETERS FROM THE EDGE OF THE NORTH AMERICAN PLATE- HOW DID THE ROCKY MOUNTAINS FORM (AND WHY ARE THEY STILL GROWING TALLER) SO FAR FROM THE EDGE OF THE PLATE?
Prediction is difficult, especially the future. -Niels Bohr
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Hiya skip
I'm not quite sure how it all works. But are they the type of mountain that is created by the folding of the earths crust, an area of land that sits in between two plates that are pushing together. Something like that, I think
Michael (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi11.photobucket.com%2Falbums%2Fa186%2Fukmicky%2Frofl.gif&hash=481319b762ee9d57cda15e90d2e83ee6)
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Your hypothesis is spot on for the Himalayas, Alps and a few other mountain ranges- but there is no evidence of a junction of plates along the Rockies. As far as I know- the North American plate extends all the way across the US (with the exception of a small piece in southern California).
Prediction is difficult, especially the future. -Niels Bohr
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Thanks for a great question Skip.
I'm stumped !..the mountains are not on the edge of the plates and Michaels
answer above doesn't cut it either eh ?...and yet these mountains are
growing !...is there some sort of lava making activity happening below,
beneath the Rocky Mountains that is pushing them up ?...there has to be
something that is making more mountain.
Men are the same as women.... just inside out !! (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.world-of-smilies.com%2Fhtml%2Fimages%2Fsmilies%2Fugly%2Fugly_bums.gif&hash=e21c0210a2673ae990b27e26bb7f6440)
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Neil- you’re on the right track.
This conundrum even stumps the folks that study plate tectonics (plate tectonicists?).
An initial short length, a bit of lengthening, and lots of shallow thrusting, is the best hypothesis put forward to date (quit panting Neil).
1. Initial short length: When the Rockies began forming, in
the Laramide orogeny (~75 to 55 million years ago), the coast was
several hundred kilometers closer. The Farallon plate was being
subducted beneath North America close to the California-Nevada border.
2. A bit of lengthening: The Great Basin has been undergoing
extension of at least 2 cm/yr for the last 16 to 20 million years
(300-400 km)- so the subduction zone was even closer yet. This is
probably due, in part, to the NA plate over-running the Farallon
spreading ridge.
3. Lots of shallow thrusting: The oceanic crust (Farallon
plate), being thinner and heavier than the continental plate, was
subducted beneath the NA plate- leading to compression and sliding
stacks of rocks along “thrust” faults long distances to the east.
Apparently, instead of sinking into the mantle at the typical angle
of around 45 degrees, the Farallon plate stayed almost horizontal,
this stacked up thrust zones much farther to the east than the
norm. Volcanism started around 50 million years ago, which is
additional evidence of a descending slab beneath the Rockies.
Present uplift of the entire Rocky Mountain region indicates that
tectonic processes are still active- i.e. that the slab is still
scraping the bottom of the crust.
Here is a normal subduction zone
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww2.nature.nps.gov%2Fgeology%2Fusgsnps%2Fpltec%2Fcontvsocn288x157.gif&hash=72d2bbd67ae4d2d0361a25a7a378e513)
Compared to horizontal slab subduction:
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww2.nature.nps.gov%2Fgeology%2Fusgsnps%2Fpltec%2Fshallowsubduct.gif&hash=cee0548a123315c40060a481dca07351)
If you’ve ever been in a room with two or more geologists, you’d
soon discover that they can’t agree on much of anything. In tune
with our disagreeable nature- there are several other hypotheses.
(BTW- Only a small piece of the Farallon plate exists today- called the Juan de Fuca plate off the coast of Oregon, Washington and British Columbia- the rest has been over-run by North America).
Subduction causes orogeny.
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Skip, you're very generous to say that I was on the right track, of course your explanation was going to be my next guess !![:D]
....Thank you for the explanation. It's all very facinating stuff.
Men are the same as women.... just inside out !! (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.world-of-smilies.com%2Fhtml%2Fimages%2Fsmilies%2Fugly%2Fugly_bums.gif&hash=e21c0210a2673ae990b27e26bb7f6440)
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I'd agree with the theory of reduction spots. As for animal tracks, if you head to Almeria in Andalucia it is possible to examine large sedimentary basins and there is evidence of the Messianian salinity crisis, proof of which can be round the whole of the med. While there we saw deer tracks.
Can't find name of locality at present though.
James[:)]
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The following pictures are from lava flows
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.nps.gov%2Fcrmo%2Fglossary%2Fpahoehoe.jpg&hash=c4dd2a7ec6a4c7c7497f6f9eb69b38d4)
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.bishopmuseum.org%2Fexhibits%2FpastExhibits%2F2001%2Fxtreme%2Fimages%2Fpahoehoe.jpg&hash=dca6f4819cc6adf3e7dddc486ce370ff)
QUESTION OF THE WEEK:
These flows have a very distinctive "ropey" surface texture. Name the flow texture?
Bonus questions:
Name the type of lava?
What does this tell you about the explosiveness of the volcano?
Where is the source of the molten rock (lava)?
Subduction causes orogeny.
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Come on peeps..have a go...I'm stumped...This is one for Exodus.
Thanks for the quiz Bass.
Men are the same as women.... just inside out !! (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.world-of-smilies.com%2Fhtml%2Fimages%2Fsmilies%2Fugly%2Fugly_bums.gif&hash=e21c0210a2673ae990b27e26bb7f6440)
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As i don't speak Hawaiian? i had to cheat. but because i cheated i learnt something, so in the end its all good.
but as a respectable member of society i feel it would be wrong of me to answer the questions.
Skip,
I know what the bottom flow is called but just one question before i go to bed and place my head on my Pillow[:)] is the top picture taken underwater.
Michael (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi11.photobucket.com%2Falbums%2Fa186%2Fukmicky%2Frofl.gif&hash=481319b762ee9d57cda15e90d2e83ee6)
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Oops!
I forgot to draw the little fishies in...
Actually, that is some sort of rabbit brush or small sagebursh growing on the flow- so not underwater. This texture probably won't form underwater- the lava cools too fast.
Subduction causes orogeny.
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The “ropey” flows are called pahoehoe (pronounced like a pig squeal), the Hawaiian word for either “run like hell”, or “does it suddenly feel hot to you?”
Actually, it means smooth lava, in contrast to aa, which is rough lava.
Pahoehoe forms when the surface of low-viscosity lava flows began to cool and develop a plastic skin, As the lava continues to move underneath, it pushes the skin into lobes, giving it the characteristic “ropey” look.
Pahoehoe only forms in basalt. Basalt is a low-silica, high temperature lava- which means low viscosity. Since basalt is low viscosity, it happily flows across the ground and doesn’t accumulate volatile components like its more explosive cousins, andesite and rhyolite. That makes basalt eruptions, such as Hawaii and Iceland, safe enough to view and study up close.
The temperature and components of basalt argue for a deep source, most likely the uppermost mantle. Basalt is by far the most common volcanic rock on earth.
Subduction causes orogeny.
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Pictured here is a primary depositional feature common in sedimentary rocks. Note the change in attitude of the beds where the person is standing from those above and below.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2F+http%3A%2F%2Fwww.ualberta.ca%2F%7Ejwaldron%2Fimages%2FsedCD384%2F13.jpg+&hash=c831f12ccfb0a749e32f5f92d673b551)
GQOTW: Name this sedimentary feature.
Bonus
What type of sedimentary rock is this?
Given the large scale of this feature, what was the most likely environment during deposition of these sediments?
Subduction causes orogeny.
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The sedimentary feature here is called cross-bedding. Cross-beds are internal sedimentary structures formed by currents of wind or water. Cross beds are deposited on the lee side of ripples (subaqueous) or dunes (wind caused)- as granular sediment (usually sand) rolls down the steep advancing edge or "foreset slope" of the dune. Commonly, the next sedimentary layer erodes the top of the cross-beds, leaving a sharply defined angular discontinuity.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwrgis.wr.usgs.gov%2Fdocs%2Fusgsnps%2Fcoast%2Fdunes%2Fimages%2Fdunefmtn1.gif&hash=9f6e6d63f8f2700ef831caf440732b23)
The sedimentary rock pictured here is a sandstone. The large scale of the cross-beds indicates it probably formed by wind-blown dunes- the depositional environment is most likely desert (possibly beach). Water-laid cross-beds are much smaller.
Subduction causes orogeny.
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(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fformontana.net%2Fshores.jpg&hash=ef614b3b5d6d2908fd8330ac45acace0)
This photo is from Missoula, Montana. Note the prominent horizontal banding, which is displayed quite well by snow on the mountain slope.
GQOTW: How were these horizontal bands formed? (the underlying bedrock is oriented almost vertical)
Bonus: What impact did this have on landforms in Washington state?
FYI: The formation of these horizontal bands and their impact was one of the most controversial geologic debates in the 1930's to 50's.
Subduction causes orogeny.
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That looks a bit like the stuff I saw on channel 5 the other night when they were talking about superfloods created by the failure of Ice dams on glacial lakes.
Learn, create, test and tell
evolution rules in all things
God says so!
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Did the bands/layers start off horizontal but got pushed up into their vertical positions as the mountain went up
Michael
HAPPY NEW YEAR (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi11.photobucket.com%2Falbums%2Fa186%2Fukmicky%2Fparty-smiley-012.gif&hash=844994fd61764508c533537d6874634d)
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Sorry if my question was confusing. The underlying bedrock is much older than the horizontal banding- bears no relationship to the banding.
Soul Surfer is on the right track, but what formed the horizontal bands?
Subduction causes orogeny.
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Watched an amazing program last night/this morning . following the expedition to discover what really happend at the bottom of the sea that caused the tsunami from last year. They went 4 months after the event an it was astonishing the pictures and technology used, and quite humbling too when you see the shear scale of things.
Seems there was an amzing uplift of about 40 meters by 750 miles width !!!...the whole worked like a zipper and took just a few seconds. The scary thing is, only part of the fault rose up and another is expected !!...at any time.
Men are the same as women.... just inside out !!
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Im not sure but I think that is a feature created by the lake that builds up when a glacier blocks a river’s path. As the lake grows it moves up the side of the valley, the banding is created by the water as it erodes the valley wall and represents the shoreline at the time? Be kind im just a student!
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Kade - I know nothing about geology, but wouldn't logic dictate that you would not, in that case, get steps? Surely the banks would be smoothed out. Steps would indicate that the water level rose, stayed level for a while, rose again, stayed level for a while and so on? Furthermore, many of the steps appear to be the same height which implies that many rises in the water level were the same. I'm not sure how likely that is to occur naturally, but I would have thought it highly improbable.
(I'm referring to the black & white photo, by the way)
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quote:
The scary thing is, only part of the fault rose up and another is expected !!...at any time
Neil - apparently the same is true of the Pakistan earthquake. Some expert on TV the other day was saying that as little 1/10th of the stress has been relieved so far. That's scary too!
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quote:
Originally posted by kade04
Im not sure but I think that is a feature created by the lake that builds up when a glacier blocks a river’s path. As the lake grows it moves up the side of the valley, the banding is created by the water as it erodes the valley wall and represents the shoreline at the time? Be kind im just a student!
Awesome- your answer is right on!
As the level of glacial dam rose, the water level in the glacial lake rises and erodes a shoreline (or strand-line). Apparently the glacier would rise in discreet steps and stay stable for a short period of time, allowing the shorelines to develope. The fact that these lines are almost perfectly horizontal indicates they were formed by water.
There is some debate as to how many times the glacial dam built up and was then breeched, each time causing vast floods that poured through Washington state and formed the "Channel Scablands".
Beginning in the 1920's, geologist J Harlan Bretz argued that many of the landforms in Washington could only be formed by a stupendous flood- but his ideas were spurned by earth science establishment, who didn't believe in catasrtophic geologic events and couldn't envision a source for such enourmous volumes of water. It was years later before Glacial Lake Missoula was proposed as the source of the water- based on the shorelines so obvious in the photo.
Subduction causes orogeny.
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A quick summary and tour of the area:
http://www.glaciallakemissoula.org/story.html
http://www.uwsp.edu/geo/projects/geoweb/participants/dutch/VTrips/Scablands0.HTM
A very readable book
Glacial Lake Missoula and Its Humongous Floods by David D. Alt
Subduction causes orogeny.
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Well I think I was sort-of right with what I said. If the level of the water rose in steps, then fair enough
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Sorry DoctorBeaver, didn't mean to ignore your answer- which as you point out is also right on!
Subduction causes orogeny.
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yeah! happy dance lol! can anyone ask questions?
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Go for it Kade04
Subduction causes orogeny.
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(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fimages.spaceref.com%2Fnews%2F2006%2FSol690B_P2564_L7_inset-B695.jpg&hash=7690ea306f1e3248b6d886cd126b8ae2)
Maybe this belongs in the "Science Photo of the Week" thread, but the reference to cross-beds in this thread made it relevant.
This photo from the Mars Rover Opportunity near the edge of Erebus Crater shows good evidence for the historical presence of water on Mars- note the "festoons" or cross-laminations (curved upward layers) that indicate water-formed ripples.
http://www.spaceref.com/news/viewsr.html?pid=19212
Subduction causes orogeny.
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Rocks can develop planar features for several reasons- the most common are bedding planes. The next most common is pictured here- in the top photo, bedding is obvious and aligned with the blue pencil, the second planar feature cuts across the bedding and is aligned with the black pencil. In the bottom photo, bedding is the crinkled colored layers while the second planar feature is almost vertical (aligned with knife):
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.anr.state.vt.us%2Fdec%2Fgeo%2Fimages%2Ffitch708.jpg&hash=c84721112f23983a31292cd0b2ba9527)
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.geosci.usyd.edu.au%2Fusers%2Fprey%2FTeaching%2FGeol-1002%2FHTML.Lect4%2FParagonFold1.jpg&hash=4431b422a463d2313b0b610a3882e12e)
GQOTW: Name this planar feature?
Bonus: How does this planar feature form? What does it tell us about the history of the rock?
Subduction causes orogeny.
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Hint:
Wonderbra -
what most men first notice about a woman wearing a wonderbra.
Subduction causes orogeny.
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Cleavage!
More commonly called "rock cleavage" or more properly called either "axial planar cleavage" or "foliation".
Occurs in metamorphic rocks that have been subjected to pressure. The pressure and heat of metamorphism change the clay minerals in sedimentary rocks into mica (several varieties). Mica has a distict planar orientation, and it grows in the direction of least pressure- which will be perpendicular to the stress field.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi12.photobucket.com%2Falbums%2Fa232%2Fyllwstnrocks%2Fcleavage.jpg&hash=97bbad786195e97ccc759cc7af3efa03)
Commonly, bedding planes will fold during metamorphism, also perpendicular to the greatest stress- so the foliation ends up being in the axial plane of the fold, hence "axial planar cleavage". The amount and orientation of foliation allows the observer to figure out the relative intensity of metamorphism and gives clues as to the true orientation of the original beds.
Subduction causes orogeny.
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quote:
Wonderbra -
what most men first notice about a woman wearing a wonderbra.
their not very well blessed ?
RE-HAB IS FOR QUITTERS.
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quote:
Originally posted by Bass
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fimages.spaceref.com%2Fnews%2F2006%2FSol690B_P2564_L7_inset-B695.jpg&hash=7690ea306f1e3248b6d886cd126b8ae2)
Maybe this belongs in the "Science Photo of the Week" thread, but the reference to cross-beds in this thread made it relevant.
This photo from the Mars Rover Opportunity near the edge of Erebus Crater shows good evidence for the historical presence of water on Mars- note the "festoons" or cross-laminations (curved upward layers) that indicate water-formed ripples.
http://www.spaceref.com/news/viewsr.html?pid=19212
Subduction causes orogeny.
Bass, may I politely disagree. I concur that this is evidence for water on Mars, but the structures to me look to be a series of seasonal dessication cracks that are stacked one upon another. To bad we can't get to the outcrop to determine the accuracy of the interpretation.
And orogeny causes uplift
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Interesting. I am seeing a cross section through a finely laminated sequence; no cross bedding; no dessication cracks. It is good to know the art of geological equivocation is still alive and well.
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(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2FScience%2FSol-1.jpg&hash=6d2bc614e5bc8caf7741550ad8a73ccb)
Alright Ophialite (rock or snake?).
The structure just off of the end of the arrow is not a cleavage related feature. It lacks one side of being a closed square. This suggest dessication to me. There are traces of the same type of feature and one whith a chip "wedged" between the to sides of a upturned bed. But I am not going to make any more of this as we will never know for sure.
What bothers me more is the origin of the pellitoidal thingies that are all over the place. Are they desert, wind-generated concreations? Can you think of another explinaiton? Weatherd out of another rock? Or other?
I am open to all as I know the laminated are faily well explained.
Jim
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[Ophiolite - ocean rocks welded to continental masses by subduction]
If you will imagine swinging the arrow around in a clockwise direction, till it is vertical, you will find it ends in a narrow column of rock, replete with laminations, slightly displaced from the adjacent blocks. I see post depositional collapse structures. Nothing more. However, you are correct: from this single photograph we are unlikely to reach a firm conclusion.
The small spherules I took to be blueberries, which were observed early on by both (?) rovers. These may be formed as concretion within the rock as a result of groundwater activity, then released by normal erosional processes. For example: http://www.spaceflightnow.com/news/n0406/16blueberries/
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I can go along with collapse structurs. Also, the hematite concreation hypothisis was first on my list. I dared not hope for oolites eroded from a less dense carbonate. And I was taught that ophiolte was a mostly mafic igneous rock with a little metamophic thrown in that is metamorphosed in a subduction that probably failed - example: the highlands of Cuba. I am a rock pounder as well, but of a much ealier vintage.
Good to know I am not alone here.
Jim
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Since JimBob brought it up-
GQOTW: What are oolites and how do they form?
Subduction causes orogeny.
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Oolites are a component of certain sedimentary rocks. However, I view everything Cambrian and later as superficial drift deposits, so I choose not to answer. Basalts are real rocks, so are eclogites.
JimBob, I will be marginally surprised if you are an earlier vintage than I. For one thing I can remember how warm the summers were in the late Cretaceous! Class of '70. Yourself?
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'66
If I only had a little humility, I'd be perfect.
----Ted Turner
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Damn. You don't live in Texas do you? Or, ever worked for Conoco?
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I do. Never worked for Conoco but had three partners that did. Timko, Lindah, Schweirkert. Obviously, working with them I lived in Houston (ICH!) for 12 years until the worldwide consuling job in my hometown came up.
If I only had a little humility, I'd be perfect.
----Ted Turner
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Picture of oolites
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.soton.ac.uk%2F%7Eimw%2Fjpg%2F3PT-oolite-with-mm.jpg&hash=c28a215fceb1fc6d97658a1ce71f6af8)
Subduction causes orogeny.
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Beautiful picture, Bass. Looks as if it cold have come from the broken well bore core obtained from the Smackover Limestone of the Gulf Coast of the US. Is the limestone pictured Upper Jurassic? If so it would be the ABOUT the same age as the Smackover. Below the Smackover is the mainly aeolian, arkosic Norphlet Sand that is then underlain by the Louann "Salt". This is a series of mixed evaporites (the core sitting on my desk is mostly gypsum) that was deposited during the opening of the Gulf basin.
I am intersted to see how this correlates.
If I only had a little humility, I'd be perfect.
--Ted Turner
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Upper Jurassic Portland Group. The photo is not mine, but I remembered the distinctive oolites from a field trip eons ago.
Subduction causes orogeny.
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The red is oxidation. The green is likely evaporite deposits from a hypersaline brine. Likely gypsum or something like that. This would be a periodic deposition process that produces the green layers you see in these red bodies. Not to sure about the decomposing plants idea. Sounds a bit far fetched. The environment was likely pretty dry.
Enjoy diversity.
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Red Sandstone fairly formed in the oxidation environment. It contains Iron oxide and probably comming out from the chemical weathering of Basic o Ultrabasic rocks. This type of rocks form in backarc basins.
Green colour representing Glauconite.
In India Vindhyan sandstone of Central province have both characteristics
lovelesh
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What is a "nick point"?
Subduction causes orogeny.
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According to the AGI Glossary of Geology ...
No, that is cheating. I am above that (right [}:)])
The mind is like a parachute. It works best when open. -- A. Einstein
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What is a "nick point"?
Subduction causes orogeny.
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According to the AGI Glossary of Geology ...
No, that is cheating. I am above that (right [}:)])
The mind is like a parachute. It works best when open. -- A. Einstein
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Here's a hint
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.wallpaper.net.au%2Fwallpaper%2Flandscapes%2FGrand+Waterfall+1+-+1024x768.jpg&hash=8aaa32b5f506bfcc49647f7f47e6f1a7)
Subduction causes orogeny.
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Magnificent picture, Bass. I would like to be there now - temp was 103 F yesterday and more of the sasme today.
Since no one else seems inclinded to answere this, let's keep it amoung ourselves, the pros.
A nick point in geology is derived from the same term in mathematics that denotes the single point where a curve changes slope abruptly.
This term is also applied to the gradient of a stream. If streams flowed over only one homogenious substratum, the gradient curve for the stream would be steep at the head of the stream and shallow at the mouth of the stream. This can occur over a very short distance within a stream's profile.
BUT, since there is a distance longer than a few hundred or thousands of feet in a streams, the substratum varies from soft to hard, ususally by sharp geologic contatcts. (The soft-hard rock interface is relative to each other.)
As pictured, the hard up-stream rock is in contact with a softer down-stream rock and a water fall is produced. The top of the waterfall is a nick point - the inflection point in the stream's gradient.
Streams can go from softer rock formations to harder rick formations: these gradient changes often result in rapids.
The mind is like a parachute. It works best when open. -- A. Einstein
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As described previously the red sediments with green mottles can be attributed to roots within fossil soils. The mottles represent areas of reduced iron, produced from anaerobic decay of organic matter in a fossil soil with a fluctuating water table. I would like to add that EXODUS is WRONG in that just because a sediment is RED does not mean it was formed in arid conditions (CHECK ALFISOL SOILS). Red soils are also found in humid climates and the drab haloed roots or burrows (green mottles)suggest that the water table fluctuates temporarily. The idea that red = arid is old news - get with it! [;)]
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Which river carries the highest sediment load? This is for the whole world.
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Is it in total discharge or per volume water per year or per day?
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No. Sediment load is the total solids moved, both the mud and small sands in suspension and larger particles moved by saltation and other methods, e.g., by ligifaction, etc., along the bottom of the stream bed.
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yes, what you say is correct, however, the sediment load can vary significantly seasonally. Are you after the river that can carry the maximum possible sediment load at any one time? or the river that carries the highest mean sediment load for say a year? I have asked around if anyone knows the answer (we're academic geologists of one type or another! [???]). There is a suggestion that a river in a glaciated area may carry the highest sed load seasonally but that a river such as the Bramahputra may carry the average highest sed load.. [:)]
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Well, then you have already got part of the answer. The Bramahputra-Ganges system has the highest sediment load, month from month. Most people think only of the Bramahputra OR the Ganges, not realizing that they merge 100+ miles from sea, forming a river with the highest sediment load, however you look at it. Also remember that the Bramaputra and the Ganges ARE rivers originating in a glaciated area. Together, they have the highest sediment load season by season.
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What type of rocks are these?
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2FF.jpg&hash=5e6b3ae5987b4f48df53f9a6ee2640e8)
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JimBob- no one seems to be willing to venture a guess? Must not be many earth scientists hanging about lately?
Nice, clear photo. The outer folded layer appears to be either quartz or quarzite (could also be calcareous?). Can't quite make out the inner rock- even though the white specks (feldspars, clastic fragments?) seem to have no preferred orientation- I would guess sedimorphic (a new geologic term!) - metamorphosed clastic rock. Could also be some sort of subvolcanic igneous- perhaps a latite- but that may be my hard-rock bias showing.
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Bass - Think gem minerals
I know that is a dead give-away, but as you noticed, there are not too many peopel who were wise in their carrier choice on this site. [;D]
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The outer one is a PEGMATITE !! - I know that the inner part of the fold is hard to see (it is a high silicate rhyolitie) so if someone got "pegmatite" I wasn't going to carp about it. The highly crystalline nature of the pegmatite can easily be seen. The formation of the crystals on the inner sides of the fissure with crystallization evolving inward until the gap between sides is closed.
Perhaps I'll find some picts that are easier.
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What place is considered to be the place most damaged by the largest earthquake in recorded history? It was an estimated 9.4 magnitude earthquake. 2004 Indian Ocean earthquake and tsunami was 9.0, and the one this question is about is, by most, considered much larger.
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I wasn't around for the largest, but I was in Alaska for 2nd largest in 1964.
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Since the Indian Ocean quake Alaska is now #3. But dang, Bass, you are almost as old as I am. The pictures of the damage on TV were in black and white!
For a hint on the question, refer to your "where in the world."
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I wasn't around for the largest, but I was in Alaska for 2nd largest in 1964.
Sorry JimBob, I didn't phrase that very well. I was but a young lad, and remember the b&W pictures on a very small neolithic TV. What I meant was that I wasn't in the vicinity of this earthquake, I was way too far north- and news traveled much more slowly in Alaska during those days.
According to the USGS, Alaska is still #2.
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The Lisbon earth quake of 1755 is the one I was looking for. 35% of the population was killed in Lisbon, 10,000 in Morocco. The resultant tsunami affected southern England, Galway, Ireland and the Antilles. It is estimated by some seismologists to have been well over 9 on the Richter Scale.
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Oops- thought you were referring to the Chilean earthquake (M 9.5) in May 1960.
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(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2FWhatInTheWorld.jpg&hash=343cdc8faaaca283fa6ce41d84ac7573)
Any idea?? This is probably too easy BUT spec-tack-u-ler
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aerial photo of desert landscape with flat-lying beds. Somewhere in Utah perhaps? Is the white snow? Can see a road in the upper left corner.
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The satellite picture is of an area about 95 mile SW of Muscat Oman. Bass is correct about the desert landscape and sediments. But the wadi (valley) cutting across the shot is pretty obviously in a thrust fault expression. The white is possibly salt. There is a lot exposed here.
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as to the red sandstone, its very common in the uk, because we used to be on and around the equator, at around 50 degrees we were in a desert environment. the action of the sun made the rock much darker red in colour and the green has got to be copper because green marks arent left by any common tree from the tertiary when the climate was that of a desert...the sandstone deposited in the uk has laminations if found on a grand scale.. the fact that the red sandstone has laminations ( deposited in dunes ) means that a tree could not survive in a sand environment alone. its got to be from the element. it wouldnt be discolouring, because in sandstones the only form of discolouring is bleaching, where by the action of water removes the oxide and leaves it white !
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did you know that after the big lisbon earthquake of 1755 the only building in the city found to be standing was a brothel .
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to the comment about alfisol soils id like to add that soils are a completely different matter as red, iron-rich subsurface horizons are only characteristics of soil and a red desert sandstone is of that name because it is lithified sand grains cemented together by silicon or various rarer types, which have been turned red ONLY by the action of the sun. If we are talking about soils its a completely different matter !
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Which river carries the highest sediment load? .... i reckon its got to be the Amazon ! i know that it transports 2 billion tonnes of particles from the andes every year over to Africa. the Andes is the fastest growing mountain range and my favourite :) apparently, according to extremescience.com For the last century the Amazon and Nile have been fighting over the title for the world's longest river. the length of them both varies across time, not sure how, but it says that the amazon carries the most amount of water. now thats got to be something... ?
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What type of rocks are these?
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2FF.jpg&hash=5e6b3ae5987b4f48df53f9a6ee2640e8)
you know, this is a really interesting picture : the rock's awesome ! im actually going to have a guess at its formation, but id like to know where the location is...? the rock in the middle is a hard rock but id guess its been metamorphosed , it probably was a mudstone at the bottom of a deep sea and then the calcarous stuff was laid on top,i think the fact its now on land would suggest isostasy was at work and it used to be in a warm tropical climate where the calcium carbonate limstone was laid down. it looks like it has a very high silica content but that could be metamorphosed Calcium Carbonate to make it marble- like .do you know what the rock is btw, ?
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the rockies are running along the conservative plate boundary known as the san andreas fault, or the massive tear in the ground between the american plate and the pacific plate.so it is a plate boundary. theyre stil growing because the plates are active
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as to the red sandstone, its very common in the uk, because we used to be on and around the equator, at around 50 degrees we were in a desert environment. the action of the sun made the rock much darker red in colour and the green has got to be copper because green marks arent left by any common tree from the tertiary when the climate was that of a desert...the sandstone deposited in the uk has laminations if found on a grand scale.. the fact that the red sandstone has laminations ( deposited in dunes ) means that a tree could not survive in a sand environment alone. its got to be from the element. it wouldnt be discolouring, because in sandstones the only form of discolouring is bleaching, where by the action of water removes the oxide and leaves it white !
Sorry, I just couldn't leave this alone.
The red coloration in sandstone is from ferric (oxidized) iron, which precipitates and is fairly insoluble in oxidizing surface conditions.
I only wish that all the green sandstones/mudstones were copper- that would make my job of finding copper deposits much easier. The green coloration is most commonly ferrous (reduced) iron.
Red sandstones do NOT require heat or a desert environment to form. Many sandstones are formed underwater- the red color only indicates that the rock contains iron. Reds are common in desert environments because the rocks are generally much more deeply oxidized.
I have been in sandstone-hosted uranium deposits which occur right at the redox boundary- the rocks are red on one side of the boundary and green on the other.
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the rockies are running along the conservative plate boundary known as the san andreas fault, or the massive tear in the ground between the american plate and the pacific plate.so it is a plate boundary. theyre stil growing because the plates are active
Check your geography- the Rockies are approximately 1000+ kilometers (600+ miles) from the plate boundary/San Andreas Fault. You have to cross the Coast range, the Great Valley, the Sierra Nevada mountains and the Great Basin before you reach the western edge of the Rockies.
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(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2FWhatInTheWorld.jpg&hash=343cdc8faaaca283fa6ce41d84ac7573)
Any idea?? This is probably too easy BUT spec-tack-u-ler
That is very cool!
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Why do hills and ridges form at a 60° angle to a strike slip fault?
If you can draw a diagram it would be even better. (Some readers are not well versed in the language of geology.) An example would also be nice.
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In a word "strain ellipse" (oops, two words)
Will draw funny circles when time allows.
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My most gracious thanks, kind sir.
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(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2FWhatInTheWorld.jpg&hash=343cdc8faaaca283fa6ce41d84ac7573)
Any idea?? This is probably too easy BUT spec-tack-u-ler
That is very cool!
It reminds me of an agate.. how they get that milky look over the top of the base color and then the shiny spots!
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I couldn't help but see some visual similarities...
[ Invalid Attachment ]
How did these layers of red cliffs form on Mars? No one is sure. The northern ice cap on Mars is nearly divided into two by a huge division named Chasma Boreale. No similar formation occurs on Earth. Pictured above, several dusty layers leading into this deep chasm are visible. Cliff faces, mostly facing left but still partly visible from above, appear dramatically red. The light areas are likely water ice. The above image spans about one kilometer near the north of Mars, and the elevation drop from right to left is over a kilometer. One hypothesis relates the formation of Chasma Boreale to underlying volcanic activity.
http://antwrp.gsfc.nasa.gov/apod/ap081006.html
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Maybe from crustal extension??? I have a friend who is a planetary geologist and an expert on Mars...Ill have to ask him and see what he says.
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What are these stripes from?? (This will be way to easy for JimBob).
[ Invalid Attachment ]
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At first glance, it almost looks like conjoining glaciers with medial moraines, but I dont think the white is ice (very little ice in the mountains). It looks like evaporites...maybe halite or gypsum.
So Im gonna take a very random guess...
Evaporites from runoff (maybe from a salty playa lake) moving over either inclined strata or an antiform/synform that has differentially weathered.
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It looks big, in a wide mountain valley with no stream, looks like a glacier, the shadows fit medial moraines, and it is supposed to be easy, so it must be a glacier. I would bet my geology degree if I had one, which I don't because I couldn't figure out anything in the field.
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The valley is certainly glacial, but at first the moraines looked FAR too large in comparison with the glacier. Also, there doesnt appear to be much of a source for flow, as none of the cirques that can be seen are full (which might explain the anemic looking glacier).
But it is a glacier...and not evaporites. Your geology degree is safe itisus [;D]
Its the Kennicott Glacier at Wrangell-St. Elias National Park in Alaska. Here is an aerial view:
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fgeogdata.csun.edu%2Falaska_panorama_atlas%2Fpage3%2Ffiles%2Fpage3-1030-full.jpg&hash=1539793ac312e25c1140853f44038383)
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What are these stripes from?? (This will be way to easy for JimBob).
Wanna make a bet - I didn't think it looked like ice at first glance. Was considering the weathering of an emergent thrust sleet. But convergent glacial outflow and the resulting medial moraines was obvious after I checked out the glacier Grasshopper came up with.
DOH!
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Frethack- I'm impressed. Not only did you come up with the right answer, you even found the right glacier. I visited this area several decades ago- I'm sure the glaciers were more extensive then than now. Was intrigued at how the glacier seemed to be more than half medial moraine material.
Least you can do now is explain to non-glaciologists what medial moraines are and how they form.
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Frethack- I'm impressed. Not only did you come up with the right answer, you even found the right glacier. I visited this area several decades ago- I'm sure the glaciers were more extensive then than now. Was intrigued at how the glacier seemed to be more than half medial moraine material.
Least you can do now is explain to non-glaciologists what medial moraines are and how they form.
Now you can see why I chose to be his Kung Geo Master. He isn't too dumb for being from Houston.
He impresses me over the phone, I hired him sight unseen.
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Thank you Bass for the compliment, and thank you JimBob for the almost compliment...hehehe
One thing JimBob forgot to mention is that Im also stubborn and pigheaded.
Anyway...glaciers begin in cirques (technically snowfields...but we'll start from the cirque), bowl like depressions in a mountain range that collect snow and ice. As a glacier forms it grinds out a larger and larger cirque. Heres an example:
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fz.about.com%2Fd%2Fgeology%2F1%2F0%2Ft%2FK%2Fcirque.jpg&hash=1489a01b56cdad22d281febd3f74778f)
As the cirque fills, the snow is compacted to firn, and then finally glacial ice and then spills over and joins with other glaciers from other cirques. A glacier is never still, and constantly flows, albeit slowly (from a few mm to a meter or more a day, depending on snow supply and relief), as it is being replenished at its head in the cirque. As the glacier flows it grinds down the rock around it, widening its valley, and transporting this ground material as a moraine, or a bank of till that lies on either side of a glacier. Here is a photo:
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.uwsp.edu%2Fgeo%2Ffaculty%2Fritter%2Fimages%2Flithosphere%2Fglacial%2Fmoraines_v_glacier_Baffin_GSC_18val_annotated_small.jpg&hash=4847ca6ffc8159dc65f08d962515818f)
Moraines contain everything from silt sized particles to boulders. There are five main types of moraines: Lateral moraines that form at opposite sides of a glacier, terminal moraines that form at the farthest extent that the glacier has travelled, recessional moraines that are deposited when the glacial ice flows faster than the cirque and snowfield can replenish (the glacier begins to recede), ground moraines which are fine silts (glacial flour) left across most of the glacial valley, and medial moraines that are formed by the lateral moraines of two joining glaciers...heres another picture!
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.mvs.usace.army.mil%2FShelbyville%2FGlaciers_files%2Fimage006.jpg&hash=7948410e92e591ccd1a42cacc24d358e) (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.geographyhigh.connectfree.co.uk%2Fs3glacgeoghigh34a.gif&hash=f6bba45fa03fb10e691f8e6c40dba5ca)
Normally the moraines arent quite as large as what Bass has posted, and the adjoining glaciers usually push the tilled material upward as the ice connects at the base like this:
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Ffarm3.static.flickr.com%2F2270%2F2060999067_5656acd30c.jpg%3Fv%3D0&hash=4e02bb527e864dcba616cce446929205)
But the glacier that Bass posted is likely in recession and has long dropped its moraine material and now flows between it. This is conjecture...not totally sure on that one.
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Love the illustrations, Frethack- nice explanation.
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You think he has been cribbing from "Holmes", Bass? I can't find my copy. Hummmmm...???
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If I get the chance to do my graduate work at University of Wisconsin - Madison, I would love to study glaciology and Quaternary climate.
Holmes? I assume its a text, and if it covers glaciers...I want it! hehehe
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Ill give it a go this time. An easy one to begin.
How is this structure formed? (bonus points if you get the name, location)
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fculture.alberta.ca%2Fmuseums%2Fhistoricsiteslisting%2Fokotokserratic%2Fimages%2Fokotoks400_1.jpg&hash=afbb2389bf05602f671aac0b49d7a961)
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(Mumble t%ww@@beedle))^^ soft rockers grumble)
Is that bedrock (as in "in place")?
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Youre on the right track...nope...not bedrock.
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Formed by karsting. I have seen similar formations in Central Texas but this could be a scene from any temperate karsted region in the world.
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Nope...not karsting. The slump in the center looks like it may have been, but no dice!
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Glacial erratic. Looks like something from Canadian Rockies- so my guess would be somewhere in Alberta? I seem to vaguely remember a whole train of similar erratics that stretched all the way to eastern Montana
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Glacial erratic in Alberta it is!
And, yes, it is part of the Foothills Erratics train, this being the largest in N America I believe. Its the Okotoks Erratic in Alberta, and is composed of quartzite from the Jasper area in the Canadian Rockies.
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OK
MY turn
What is this??
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Hmmmm....Im gonna say multiple phragmocones from some species of cephalopod...possibly nautiloids?
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Strait ammonites they are.
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This structure is magnificent! What is it and how did it form?
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi481.photobucket.com%2Falbums%2Frr176%2Ffrethack%2FPretty.jpg%3Ft%3D1231777876&hash=d512e57cfefbba0bbfe5071116223301)
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I can't tell - I already know since you told me yesterday during the Pittsbugh- San Diego football game.
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Being an old spelunker, the stalactites are obvious in the background. The big moth is intriguing- then I noticed the horizontal growths. My guess is helictites. Where is the cave?
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Yep, helictites. The cave is Sonora Cavern and it is unbelievable.
From Wiki: The founder of the National Speleological Society, Bill Stephenson, said of the cave after his first visit: "This is the most indescribably beautiful cave in the world, its beauty cannot be exaggerated, not even by a Texan."
My wife took me there for my birthday two weeks ago :) Because it was my birthday and I was a geoscience student, the guide took us into two rooms that are solely reserved for scientists...I was in heaven!
The formation is called "The Butterfly" and is the only known double fishtail helictite in the world. Unfortunately, some college kids broke off about a third of one of the wings in 2006, but after a little lobbying, the Texas legislature made it a felony to deface a landmark. Since the guy had never been charged before the law change, he is now charged with a felony. [;D] Dont mess with Texas!
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Gosh, I wish I were that smart.
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What is the oldest Fossil life form and how old is it?
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You? 564412354688886421354 years old? [:)]
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Bristlecone pine trees? 4600 years?
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You? 564412354688886421354 years old? [:)]
Oh, was that thing that woke me up the Big Bang? Must mean I am Brahman, the first cause. I open my eye and a universe is created,I close my eye and it ceases to exists.
You know, when you have that much power, you hardly notice it.
NO, I am not the oldest fossil on the earth.
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Bristlecone pine trees? 4600 years?
Yes, it is the bristle cone pine as the oldest Living complex life form. I have clarified the question -
What is the oldest known fossil life form and how old is it?
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Some sort of cyanobacteria-like fossil?
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Yep, algal mats, not stromatolites, 3.2 billion years old - found in South Africa
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what happened to the 3.4 to 3.5 B cyanobacteria fossils found in the Barberton Greenstone belt in South Africa?
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They are probably still there. And there is good evidence that they are life forms older than 3.5 years old. This date comes from the greenstone itself and is thus from a metamorphic rock.
But http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1578735
When I ran across this on the BBC web site it was billed as the oldest fossil in existence.
I feel like Eeyore.
Can I take any more?
Thank you, Friend Bass -
You made me an As*
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(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Flol%2F15.gif&hash=542cfd4ca9e8ca912a6f9ff13d396a18)
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Take no offense master JBs
I bow before your expertise
As to your poetry, I pass
Cause Eeyore’s already an as*
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This should appeal to the chemists as well.
Why do speleothems grow fastest in dryer winter conditions with low rainfall and low CO2 (g) in the cave atmosphere?
Just had a speleo-climatology lecture today...hehehe
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Why should we care???
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Why should we care???
Because speleothems are used as proxies for rainfall/climate data! If they are only recording winter/early spring rainfall then we will surely have to rethink how we use them.
Heres the stoichiometry...maybe that will help?
CaCO3 + 2H+ = Ca2+ + H2O + CO2(gas)
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Does this mean spelunkers will die of carbon dioxide poisoning?
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Spelunkers? [???]
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Spelunkers? [???]
Why yes, C4 It is always useful to have a dictionary around or on yuor computer. Here iss what mine says:
spe-lunk-er (spi lung'kuhr) n.
1. a person who explores caves, esp. as a
hobby.
[1940-45; < L spelunc (a) cave (< < Gk spêlynx, s.
spelyng-, akin to spélaion; cf. SPELAEAN) + - ER 1]
Derived words
--spe-lunk'ing, n.
frethac tried to explain it to me - the production of CO2 form plant material during winter inhibits the chemical process he posted and thus somehow causes solubility of the carbonate to be less. - heck I'll get him to post it when he gets home from work. As a lowly student - albeit an excellent one - he needs to have a part time job. I will call him and put us all out of our misery with a decent answer to the poser he posted.
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Heres the stoichiometry...maybe that will help?
CaCO3 + 2H+ = Ca2+ + H2O + CO2(gas)
It would also help to post the correct stoichiometry...sorry guys! [;D]
Ca+2(aq) + 2HCO3-(aq) <---> CaCO3(s) + CO2(g) + H2O(l)
The above is the degredation of bicarbonate (a product of carbonic acid) into calcium carbonate.
Biological production during the spring/summer months generally increases soil CO2, which dissovles into groundwater, forms carbonic acid (and later bicarbonate), and seeps into the cave system. As excess CO2 builds up from increasing soil production and limited ventilation of the cave atmosphere the reaction that forms the speleothems (stalactite/stalagmite/helectite etc.) is driven backward, which keeps the bicarbonate in solution and limits speleothem growth.
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Dear All
How are you, I have a unique problem for you guys. I have a Sand stone(image is attached), This sand stone is having base colour of yellow. and there are Red and White Veins in between. These white veins are made of Milk Quartz. We want to change the colour of these white veins into red. Please tell us the way to do it.
regards
varun agarwal
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History of this rock??
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A re-worked arenite peeble that has under gone tensional stresses associated with some orogeny???(quartz veins?) Too, some graded bedding indicative of the paleo flow regime in the original environment.???
hey, I'm, trying.
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Picked this up in NW Montana yesterday whilst waiting for a horse show. Looked like lots going on for such a small rock - just thought I'd throw it out for discussion. Exposures in the area are upper Belt Supergroup (Missoula Group).
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When I look at this rock, I see mud rip-ups, soft sediment deformation, cross-beds and a graded bedding mix of iron stained mudstone, siltstone and sandstone. Suggests shallow water deposition with differing energies, slumping and channels. The rock has been slightly metamorphosed to argillite/siltite/quartzite. After millions of years of burial, this rock was uplifted and eroded, tumbling down some stream or river to give it a rounded shape.
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WHAT A ROCK!! Find another like it - I want one!!!
And dang, Bass, you don't need to team up with a sedimentologist for your work. Why did you do it?
There looks to be a bit of bio-turbation (see picture below) but it probably isn't, what with it being Mezoproterizoic. Of course you never know what was around 1.6 Billion Years Ago. Aliens? I'll bet it is just a strange looking rip-up clast
Lastly, what struck me about this specimen was is sub-hexagonal shape. That is easily produced by one set of stress, a shear and the two accommodation ax-es. (hyphen for pronunciation - it is the correct plural) The stress regime was perpendicular to the bedding planes. There are also small-scale load cast? visible.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2Fmulit-sedimentaryfeaturedcopy.jpg&hash=8a940b8676026c15e1c4e081274771b7)
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Don't have another one...
would a nice breccia do?
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Why can a magmatic nickel deposit could not exist in a felsic host rock?
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Nickel (along with chrome and pge) has an affinity for ultramafic rocks. They form as immiscible minerals that accumulate due to their density in bands in the crystallizing magma (that is they rain down as discrete particles).
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The thing is, I don't really have an answer.... [::)]
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Hey dude - we are geologist - not chemist or even geochemist. Those guys are weird - really weird!
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Okay dudes, how about: What occurs when a smectite mineral swells?
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It gets a smec tighter [::)]
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Smectites are phyllosilicate clays (montmorrillonite, nontronite) composed of an octohedral sheet sandwiched between two tetragonal sheets. (just thought I'd throw a little jargon out there- helps to keep the rifraff in the profession)
What that mouthful means is that, when water is added, the clay can absorb the water and trap it between the sheets, which causes swelling. Water is lost between the sheets as conditions turn dry, allowing shrinkage.
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It becomes FURTHER hydrated. Water in the interstitial spaces of this phyllosilicate make it slick as greased owl sh1t.
Just what are you looking for C4 - some chemical reaction? Or do you wear cosmetics made of this stuff and are having problems when your face gets wet?
I can't help with that.
Will call later today, Bass
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It was simply a geology question of the week (supposedly).
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Since I'm new here, I'm not sure whether or not the question has been answered. But in the event that it hasn't I offer this.
It is correct that the red color in sandstone is due to iron oxide. As for the patches of green, the primary minerals that make up sandstone are quartz and feldspar. Therefore, I would imagine that the green color is due to the alkali feldspar, microcline (KaAlSi3O8). But, I'm just guessing here.
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iron on the red and iron on the green, just different valences for the Fe. Copper is a very small, remote possibility for the green. It is a very unusual possibility.
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I like Dr Ward's reference to this massive deposit of red soil in his African hunt for animals from the K/T die off. He looks around and it is red everywhere. And he is not high in elevation; it is oxidized iron. The seas had receded although he doesn't state how far, I propose as low as only a couple miles of water from the sea bed up. If one was to seriously consider that our E is circled N and S of the Equator by plasma as NASA proposes, then it is not inconceivable that the seas experienced massive beyond thinking electrical charges ala Birkeland current and that this charge separated the contaminants from the water. The result of course, would be pure water but incomplete from the point of view from all living creatures which need minerals to survive. It may have begun farming and cattle raising for the protein and the never-ending war for possession of surface water ala Jericho and its ever-flowing spring sufficient to wash the accumulation of salts away. A prize fought over ever since.
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How do you tell the hardness of a rock? What is a streak. And why are these two things important in identifying rocks? How do you figure out these two properties?
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How do you tell the hardness of a rock? What is a streak. And why are these two things important in identifying rocks? How do you figure out these two properties?
is streak dust for lab testing? do the same tests for minerals apply for rocks too [1 (https://geology.com/minerals/mohs-hardness-scale.shtml)]