Notices
Results 1 to 31 of 31
Like Tree5Likes
  • 2 Post By adelady
  • 3 Post By John Galt

Thread: Round stone puzzle

  1. #1 Round stone puzzle 
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    A little conundrum for the big brains in this forum.

    I live on the side of a hill overlooking the sea, and below me - 90 metres down - is a beach covered with nice smooth round stones.

    I was doing some digging, and found a similar round smooth stone. Not identical, since the beach stones are grey and this one was mostly black. The thing is, the stone I found was under a metre of top soil. Not in clay, or sandstone or anything like that - just in the top soil, but a metre down. This is the only such smooth stone I have found in that region.

    The way I see it, the stone has been there for hundreds or thousands of years, but not geological eons. It must be too recent for it to be related to major geological movements like sea level rise and fall, or land rise or fall. Being in top soil, it must have been placed there, but a metre down makes it probable that it pre-dates humans here in NZ.

    How do you think it got there?


    Reply With Quote  
     

  2.  
     

  3. #2  
    Moderator Moderator
    Join Date
    Nov 2011
    Location
    city of wine and roses
    Posts
    6,222
    Well, we have subsidence, floods, storms, landslides to start with. At least NZ doesn't have an abundance of burrowing native animals that might have accidentally dislodged such things from the surface. I'm not so certain that it pre-dates human occupation, though.

    Of course you might perhaps settle some of these questions if you go out with your trusty spade and dig up a square kilometre or two to the same depth to see if these things are common or rare. (Always willing to offer new hobby opportunities to anyone, don't bother to thank me.)

    Might be worth while getting someone to check the composition of your rock and one of those beach rocks. Whether the result would tell you anything interesting is another issue entirely.


    sculptor and dmwyant like this.
    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
    Reply With Quote  
     

  4. #3  
    Forum Radioactive Isotope sculptor's Avatar
    Join Date
    Apr 2012
    Posts
    4,211
    fired from a ships canon, it buried itself in the soil
    .............
    alf a mo

    What size is it?
    round as in spherical?
    Reply With Quote  
     

  5. #4  
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    Well, I do have a possible hypothesis myself. I wondered if it might be a moa gizzard stone???
    Stones of the moa | Stuff.co.nz

    It is not spherical. Kind of ovoid, but not truly symmetrical, but well smoothed, as you would expect if it was a beach stone.

    I doubt if it got there as a result of anything catastrophic. The top soil layer is fairly even, a little over 3 metres thick. The stone was definitely part of the top soil, but 3 metres down makes me think it had been there a long time.
    Reply With Quote  
     

  6. #5  
    Administrator KALSTER's Avatar
    Join Date
    Sep 2007
    Location
    South Africa
    Posts
    8,229
    Volcanic ejecta?
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
    Reply With Quote  
     

  7. #6  
    Forum Masters Degree MrMojo1's Avatar
    Join Date
    Mar 2012
    Location
    South Florida, USA
    Posts
    618
    I would speculate in the same vein as Kalster (Volcanic Ejecta). Without any further information than "smooth black stone" I guess it may be similar to the black stones of Punalu'u Beach. I would suggest testing the stone for mineral content.

    The volcano Krakatoa is near your geographic region and has a history of violent eruptions.

    With a Volcanic Explosivity Index (VEI) of 6,[2] the eruption was equivalent to 200 megatons of TNT (840 PJ) about 13,000 times the nuclear yield of the Little Boy bomb (13 to 16 kt) that devastated Hiroshima, Japan, during World War II, and four times the yield of Tsar Bomba (50 Mt), the largest nuclear device ever detonated.
    The 1883 eruption ejected approximately 21 km3 (5.0 cu mi) of rock, ash, and pumice.[3]
    The cataclysmic explosion was faintly heard as far away as Perth in Western Australia, about 1,930 miles (3,110 km) away, and the island of Rodrigues near Mauritius, about 3,000 miles (5,000 km) away.[4]
    Additionally, there are many other volcanoes in the area of Indonesia, Japan, and Philippines whose eruptions have had significant global effects (e.g. Year Without a Summer).
    Reply With Quote  
     

  8. #7  
    Moderator Moderator
    Join Date
    Nov 2011
    Location
    city of wine and roses
    Posts
    6,222
    Moa? Bother. I thought about them for a moment but I didn't check any details.

    They're certainly the best candidate for moving a single, isolated rock to an unusual place.
    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
    Reply With Quote  
     

  9. #8  
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    Quote Originally Posted by KALSTER View Post
    Volcanic ejecta?
    I have never seen such a rock that is smooth and round like a beach stone.
    Reply With Quote  
     

  10. #9  
    Forum Senior
    Join Date
    Sep 2006
    Posts
    399
    The real question is: why on Earth were you digging 3 m deep holes in your garden?

    Killed anyone recently?
    Don't bother visiting my Earth Sciences forum, it died a death due to lack of love
    Reply With Quote  
     

  11. #10  
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    Quote Originally Posted by billiards View Post
    Killed anyone recently?
    Nah.
    That's a bad habit and I am trying to give it up.

    I am doing a bit of landscaping, and I dug a trench to lay a drainage pipe.
    Reply With Quote  
     

  12. #11  
    Time Lord Paleoichneum's Avatar
    Join Date
    Oct 2008
    Location
    Washington State, USA
    Posts
    5,008
    Hmm, interesting conundrum. What was the glacial activity in your area like during the last iceage?
    If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -Thorin Oakenshield

    The needs of the many outweigh the need of the few - Spock of Vulcan & Sentinel Prime of Cybertron ---proof that "the needs" are in the eye of the beholder.
    Reply With Quote  
     

  13. #12  
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    I am too far north for glacial activity.

    I wonder about the black colour. The stone is otherwise identical to the smooth rounded beach stones 90 metres below. Is it possible the top soil may have stained the stone black?

    If not a moa, could some other bird have moved it?
    Reply With Quote  
     

  14. #13  
    Time Lord Paleoichneum's Avatar
    Join Date
    Oct 2008
    Location
    Washington State, USA
    Posts
    5,008
    Were you too far north for Glacial activity during the last Glacial Maximum?
    If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -Thorin Oakenshield

    The needs of the many outweigh the need of the few - Spock of Vulcan & Sentinel Prime of Cybertron ---proof that "the needs" are in the eye of the beholder.
    Reply With Quote  
     

  15. #14  
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    Paleo

    I live in the far north of New Zealand. The glacial maximum covered half the South Island with ice, but little of the North island. My home is further north than any ice reached.
    Reply With Quote  
     

  16. #15  
    Universal Mind John Galt's Avatar
    Join Date
    Jul 2005
    Posts
    14,168
    I don't have an explanation for your stone, but you reminded me of something I used to do. I liked to take rocks from one location and leave them, adjacent to countryside paths, beside completely different rock types, but placed as naturally as possible. My intention was to cause at least a few moments of puzzlement for any passing geologists.

    Everyone should have a hobby.
    marnixR, KALSTER and sculptor like this.
    Reply With Quote  
     

  17. #16  
    Time Lord Paleoichneum's Avatar
    Join Date
    Oct 2008
    Location
    Washington State, USA
    Posts
    5,008
    Any paleostream beds or other types of extinct water features?
    If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -Thorin Oakenshield

    The needs of the many outweigh the need of the few - Spock of Vulcan & Sentinel Prime of Cybertron ---proof that "the needs" are in the eye of the beholder.
    Reply With Quote  
     

  18. #17  
    Forum Senior
    Join Date
    Sep 2006
    Posts
    399
    Take that little pebble and throw it as far as you can. Problem solved.
    Don't bother visiting my Earth Sciences forum, it died a death due to lack of love
    Reply With Quote  
     

  19. #18  
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    Quote Originally Posted by Paleoichneum View Post
    Any paleostream beds or other types of extinct water features?
    Sorry, no.

    I am inclined to a biological explanation. Something - probably not human - carried the stone??
    Reply With Quote  
     

  20. #19  
    Forum Radioactive Isotope sculptor's Avatar
    Join Date
    Apr 2012
    Posts
    4,211
    gastrolith?
    Reply With Quote  
     

  21. #20  
    Forum Senior
    Join Date
    Sep 2006
    Posts
    399
    Quote Originally Posted by skeptic View Post
    Quote Originally Posted by Paleoichneum View Post
    Any paleostream beds or other types of extinct water features?
    Sorry, no.

    I am inclined to a biological explanation. Something - probably not human - carried the stone??
    Sure. That's how science works... I think ..
    Don't bother visiting my Earth Sciences forum, it died a death due to lack of love
    Reply With Quote  
     

  22. #21  
    New Member
    Join Date
    Sep 2012
    Posts
    1
    What's the recent history of residence for your home? You have found this stone by digging to landscape the garden - could others before you have worked the topsoil?

    It would help to know the composition of your topsoil and the subsoil strata to work out the story and, also, where have the beach pebbles come from? Presumably they have been eroded out of the hill. The colour difference may be explained by weathering and erosion of the beach pebbles. Perhaps your pebble isn't on it's own in the topsoil?
    Reply With Quote  
     

  23. #22  
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    aelf

    Recent history.
    My wife and I built the house, so no domestic use before us. We clear a small amount of scrub that was regrowth after pastoral farming. The forest was cleared and planted in grass, and later reverted to scrub before we came along.

    Under our topsoil is what I call rotten rock. Brittle and broken rock of volcanic origin, and then under that is the parent rock.

    The beach pebbles appear to have been thrown up on the beach by wave action, but are originally of volcanic rock origin - just well weathered by water movement. The pebble is not the only piece of rock in the topsoil, but it is the only one that is smoothed and rounded, as if by river or beach action. The other bits are essentially the same as the underlying rotten rock.
    Reply With Quote  
     

  24. #23  
    Geo
    Geo is offline
    Forum Junior
    Join Date
    Nov 2009
    Location
    New Zealand
    Posts
    273
    It must be too recent for it to be related to major geological movements like sea level rise and fall, or land rise or fall. Being in top soil, it must have been placed there, but a metre down makes it probable that it pre-dates humans here in NZ.
    Reply With Quote  
     

  25. #24  
    Forum Bachelors Degree dmwyant's Avatar
    Join Date
    Apr 2012
    Posts
    456
    Just a thought regarding the coloration you have noted. The stones upon the beach are under consistent solar exposure which can cause a bleaching where this stone was devoid of same exposure and has retained a dark color. Just a thought. I would say take it and a beach stone to a geologist and let them run an analyses.
    Not all who wander are lost... Some of us just misplaced our destination.

    I would rather be a superb meteor, every atom of me in magnificent glow, than a sleepy and permanent planet. The proper function of a man is to live, not to exist.
    -Jack London
    Reply With Quote  
     

  26. #25  
    Forum Freshman
    Join Date
    Nov 2012
    Posts
    9
    Quote Originally Posted by skeptic View Post
    A little conundrum for the big brains in this forum.

    I live on the side of a hill overlooking the sea, and below me - 90 metres down - is a beach covered with nice smooth round stones.

    I was doing some digging, and found a similar round smooth stone. Not identical, since the beach stones are grey and this one was mostly black. The thing is, the stone I found was under a metre of top soil. Not in clay, or sandstone or anything like that - just in the top soil, but a metre down. This is the only such smooth stone I have found in that region.

    The way I see it, the stone has been there for hundreds or thousands of years, but not geological eons. It must be too recent for it to be related to major geological movements like sea level rise and fall, or land rise or fall. Being in top soil, it must have been placed there, but a metre down makes it probable that it pre-dates humans here in NZ.

    How do you think it got there?

    It depends on how old the top soil is. Its possible that the top soil was placed there just prior to the building of your house or property on top of it. In which case it could be just decades old. Especially if its a beachhouse or something that needed a level surface before being built.

    Basically, you would just have to figure out if the top soil is native or not.
    Reply With Quote  
     

  27. #26  
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    The top soil looks pretty damn native to me. The whole site was covered by regenerating forest before we built. Before that, it was grassland - cleared for pasture, and before that, it was native rain forest. I seriously doubt there was any disturbance of the top soil. Our house is the first such development on that site.

    I am inclined to the moa gizzard stone hypothesis. Those gizzard stones are known to be normally well rounded, and the moa could carry them some major distance.
    Reply With Quote  
     

  28. #27  
    Forum Ph.D.
    Join Date
    Jul 2011
    Posts
    984
    The gizzard stone hypothesis sounds likely, particularly if it is the same material as the beach stones. Did the native people use slings? A sling stone would end up in a place distant from its origen. I my area all the stones are rounded. The glaciers have scraped over New England several times. There is nothing like being dragged a few hundred miles under a mile of ice to put a nice smooth finish on stone.
    Reply With Quote  
     

  29. #28  
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    No, the Maori people did not use slings. Nor did the glaciers reach here. It is too far north.
    Reply With Quote  
     

  30. #29  
    Time Lord Paleoichneum's Avatar
    Join Date
    Oct 2008
    Location
    Washington State, USA
    Posts
    5,008
    hmm Gizzard stone,,,,, What species of Moa were in your area?
    If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -Thorin Oakenshield

    The needs of the many outweigh the need of the few - Spock of Vulcan & Sentinel Prime of Cybertron ---proof that "the needs" are in the eye of the beholder.
    Reply With Quote  
     

  31. #30  
    Forum Radioactive Isotope skeptic's Avatar
    Join Date
    Nov 2008
    Location
    New Zealand
    Posts
    4,843
    According to local books, the most common moa species in my area was mantell's moa, which weighed around 30 kilograms. Not the biggest moa species, but still a very big bird by any other standard.
    Reply With Quote  
     

  32. #31  
    Time Lord Paleoichneum's Avatar
    Join Date
    Oct 2008
    Location
    Washington State, USA
    Posts
    5,008
    Sounds possible then
    If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -Thorin Oakenshield

    The needs of the many outweigh the need of the few - Spock of Vulcan & Sentinel Prime of Cybertron ---proof that "the needs" are in the eye of the beholder.
    Reply With Quote  
     

Similar Threads

  1. earth revolves round moon!
    By precious in forum Astronomy & Cosmology
    Replies: 11
    Last Post: November 29th, 2011, 09:43 AM
  2. Merry-go-Round on a train?
    By chancerph in forum Physics
    Replies: 3
    Last Post: April 26th, 2011, 07:21 PM
  3. New kind of explosive low-velocity round.
    By Pomegranate Cameron in forum Military Technology
    Replies: 25
    Last Post: March 3rd, 2011, 09:55 PM
  4. Old Stone Age
    By Twittery in forum History
    Replies: 3
    Last Post: November 6th, 2009, 06:08 PM
  5. swedish stone?
    By goodgod3rd in forum Earth Sciences
    Replies: 5
    Last Post: March 12th, 2008, 08:53 AM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •