Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: neilep on 26/05/2004 16:43:18
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hello science People..
There's a sh*it load of sand out there isn't there ?
I was wondering where does all the sand come from ?....how deep does sand go in your average run of the mill sandy desert ?...did sand start off as big rocks and is it due to erosion via wethering etc..?
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Yep, I would've also guessed that sand comes from the weathering of rocks especially sandstones.
As to your second question, maybe few metres of sand then followed by layers of small rocks? Anyway, Richard is the person to ask.
Angel
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Then it stands to reason that eventually the sand will wheather down to fine particles of dust !!.....Yikes !!..I'd better get down to the beach before that happens !!!
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Bear in mind that the fine dust particles will eventually turn into rocks once again but that over millions of years.
Angel
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Is that so ?...I never really thought about it like that ?...how does that happen ?...do they get together and decide to make a rock group ?[:D][:D]....seriously....I did not know that...!!...thanks.....
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There are more stars in the universe than there are grains of sand on Earth.
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Yep...I heard that there's (a rough guestimation) there could be anything from 1000 to 1000000 stars for every grain of sand on Earth.........that's a lot !!.....and to think that some people think that this planet holds the only life in the entire Universe is preposterous eh ?....and that's what I have to say about that.
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And in one grain of sand there is enough atoms, to encode enough data to store all of the humanraces written/printed knowlege, EVER. That includes duplicates i think :S.
wOw the world spins?
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quote:
Originally posted by cuso4
Yep, I would've also guessed that sand comes from the weathering of rocks especially sandstones.
Angel
Remember angel, that sandstones originally formed from sand... [:o)]
It is true that sands are formed through the weathering of rocks... Weathered granites are excellent producers of sands due to their high levels of quartz (sands are predominantly quartz which is silica). Other volcanic rocks are also good for making sands. Such sands are often black http://www.chpc.utah.edu/~mcuma/images/hawaii/punaluu.jpg. Sands do take time and large amounts of energy to form through the grinding and collision of rocks in rivers or coastlines. But as mentioned by angel,they can later undergo burial and subsequent lithification (turn to rock).
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Hello....science people...I need you help...
I want ask..how might sand from in nature???where would" shaking" come from in nature??
Thank you!!!
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Actually, if you are walking on the white, sandy beaches in Hawaii and such, altmost all the sand comes from the parrot fish's rectum.
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What about beaches that are quite rocky ?...what poor rectum does that come out from ?
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quote:
Originally posted by neilep
What about beaches that are quite rocky ?...what poor rectum does that come out from ?
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Turdles. Dem big ones. [:D]
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And I always thought those were eggs they were laying??
Prediction is difficult, especially the future. -Niels Bohr
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acutly most of the sand on beaches is from crashed shells n corel
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The white and fine sand that looks like powder comes originally from corals, but have been made into the soft sand by the parrot fish.
"For instance, Barbados has gorgeous sandy beaches. Where does this beautiful soft white sand come from that looks so splendid against the turquoise water and red-gold sunsets?
How many residents or visitors enjoying the day at our beautiful beaches realize that the humble parrot fish is largely responsible for their enjoyment? Why? Because the average parrot fish, by nibbling away at the algae on coral, produces a ton of white sand a year! A ton of sand! Imagine! And also imagine how long we would continue to have such beautiful beaches - and the enjoyment and tourist dollars they bring - - if our wetlands become too polluted and degraded to support parrot fish?"
http://usembassy.state.gov/posts/bb1/wwwhwetlands.html
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Strange when one considers that the sands were once fertile soils, supporting a massive number of animals plants and forests. Fossilised tree trunks from the worlds deserts are now saught after to become polished coffee tables in the afluent west. The Sahara was once noted as the bread basket of the world. Now it can hold 2x Australia, which itself is almost all desert or semi desert.
First the forests were removed or burned where they stood, then grasses were grown to fuel the majestic buildings of many lost civilisations around the globe. Then the ground became devoid of organic material due to its over exploitation. The rains began to fail and the soils blew away on the winds, much as they did in the American Dust bowel,leaving behind the grains of sand as a somber reminder of the folly in growing grain where once proud forests stood. And when it did actually rain on the already impoverished soils, there were huge floods which swept away anything remotely less dense than a grain of sand! Sound familiar to anyone?
Food for thought.
Andrew
Death is natures way of telling us to slow down.
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Your post suggests that human activity caused the formation of the Sahara desert. You may be putting the cart before the horse.
Geological evidence suggests that Sahara desertification, and deforestation, started with abrupt climate changes around 2 million years ago. The Sahara is a desert due to climatological changes.
A quote from the USGS site on desertification suggests that human activities have minimal impacts on desertification:
"The world's great deserts were formed by natural processes interacting over long intervals of time. During most of these times, deserts have grown and shrunk independent of human activities. Paleodeserts, large sand seas now inactive because they are stabilized by vegetation, extend well beyond the present margins of core deserts, such as the Sahara."
Prediction is difficult, especially the future. -Niels Bohr
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It matters not which species destroys coastal vegetation, once it has gone the sands immediately warm under the sun and an impressive thermal barrier rises high into the air, the same thermal barriers that carry migrating birds to and from Africa and the Middle East!
But there is another side shoot from thermals rising into the air from coastal areas. In addition to providing a cushioned invisible airway for migrating birds and causing aircrafts to endure a roller coaster ride over thermals, known as turbulance. These thermals provide a barrier against ocean born moisture from crossing onto the land. This is precisely why clouds and mist are observed to roll along a coastline, particularly the coastlines of a desert.
Once this barrier is in place, a significant reduction in rainfall will undoubtedly ensue further inland, adding to the risk of forest fires as they become tinder dry.
The funny thing is, one does not need to look into history to see if this is possible! It is happening right under our noses and it's happening now.
In Asia, the Tsunami has wiped out a phenominal amount of coastal vegetation around Thailand, Borneo, Indonesia. Is it a coincidence that an unusual drought is occuring in these and the surrounding countries?
Maybe the dinosaurs in their infinate wisdom were sound environmentalists and did not over exploit the coastlines and river banks by removing all of the vegetation.
And what about the water erosion marks on the sphinx, proven to be because of rain rather than arid sand erosion? coincidence?
One small mangrove forested island off the coast of India had ample moisture from the sea. Then they removed the mangrove forest for fuel, and grew grasses for cattle feed instead of growing more trees.
Today this island is a desert. Bone dry and scattered with the remains of cattle.
Who is to say that mankind is not as old as coal?
Death is natures way of telling us to slow down.
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and here is a piccy of that coastal moisture,torbay devon
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi48.photobucket.com%2Falbums%2Ff238%2Frayhinton56%2FPicture108.jpg&hash=e3fc2684a2e8bae2f000c3543ed859c9)
taken by yours truly.
RE-HAB IS FOR QUITTERS.
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Where does sand come from that is simple when water bangs against rocks it weres them down a little. That little bit that came down is sand
- Big T
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Hi Neilep,
basically sand is formed from the erosion of mountains ie: the rock cycle usually starts from mountain building ( either plate collisions or intrusive material ( granite etc) into country rocks then erosion/weathering of both existing rocks and intrusions and finally with transportation and deposition. However, this is a very simplified explanation but has absolutely nothing to do with man's intervention, unless he (or she) was around over a billion years!
The sand most of us see around our coastlines in the UK for instance are formed mainly from felsic materials such as the volatiles of granitic type intrusions ( quartz and feldspars which are the last minerals to form from molten magma during it's cooling process which intrudes into country rocks) usually give a fine lighter colour because of their mineral content, but there are many other sources of material as mentioned in other members postings which form different sands ( some contain bio clastic material - skeletal etc). Material scraped up and re-deposited due to glacial movement also produces very different, often very course sands untypical of the normal weathering processes.
Eventually, all weathered material will be buried in our oceans and through diagenesis, form new rocks. The lithology will depend on the depth of water mineral content and the depth of burial.
Deserts are usually indicative of sub-equatorial regions of the world and ancient desert sands can be found in Britain, typically of Devonian and Permian periods, most likely due to the plate-techtonic movement which would place what we now call Britain, a little above and below the equator during the periods mentioned, similar to the latitude of the Sahara of today.
This can be confirmed by the coals found in Britain which were formed from tropical vegetation of paleo-equatorial regions during the Carboniferous period ( which sits between the Devonian and Permian periods).
I did my university disertaion on the Carboniferous Cyclothems of the Dinatian / Namurian period of Northern England - though not exactly relative to deserts, it explains the relationship of rock cycles due to erosion, sea transgressions and regressions and the rocks that form from these processes and a worthwhile read for those interested. These cycles formed a repeated pattern and I noted at least seven of these in the area I investigated were produced during the periods I mentioned, which are quite short in relative geological time, so it gives an insight into the cyclicity of the rock cycles and the conditions of the time of deposition.
Hope this info may help but it is only a very basic elementary explanation.
Tony
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all i know is that loads of this eroded rock turns up in my chips at the beach.
hey,why arent they called eroded-rockdals.
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I just noticed this site by searching on grains of sand on earth, it is a fact I constantly bore people with. Anyway all you clever people, well I do have an MSc but that was more by luck than judgement, the best beer is in the South, its just fizz North of Watford.
Talking about grains do you realise there are 'orrible crawly things just like you and me up there worrying about their mortgage and sailing handicap !!
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I was strolling along my local beach the other day when I heard a female voice calling for help,I was surprised to find a gorgeous looking girl buried up to her neck in SAND! "Please get me out" she cried, Oh righto I said....but whats in it for me?,SAND she replied!
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it looks like sand comes from more than one source,erosion of rocks,parrot fish poop,and people scratching i love tracy,or the like in stone,if you know chesil beach dorset,you will know that the pebbles at the eastern end of the beach are v-large,at west bay,14 miles away to the west,are tiny,almost sand,due to the seas action,and currents,a very graphic example for anyone.
http://www.armybarmy.org