Quantcast

Mountains not as stable, Wits researchers prove

New evidence by South African researchers has shown that mountains are not as stable as previously thought.

Lightning strikes causing rocks to explode have for the first time been shown to play a huge role in shaping mountain landscapes in southern Africa, debunking previous assumptions that angular rock formations were necessarily caused by cold temperatures

Professors Jasper Knight and Stefan Grab from the School of Geography, Archaeology and Environmental Studies at Wits University used a compass to prove that lightning is responsible for some of the angular rock formations in the Drakensburg.

“A compass needle always points to magnetic north. But when you pass a compass over a land’s surface, if the minerals in the rock have a strong enough magnetic field, the compass will read the magnetic field of the rock, which corresponds to when it was formed,” said Knight.

“In the Drakensburg, there are a lot of basalt rocks which contain a lot of magnetic minerals, so they’ve got a very strong magnetic signal.”

drakensberg not stable

He added that readings showed a dramatic shift in the polarity of rocks where lighting was known to have struck. This indicates that the phenomenon had the ability to melt the rock and which took on the polarity of the Earth when it cooled again.

“The energy of the lightning hitting the land’s surface can, for a short time, partially melt the rock and when the rock cools down again, it takes on the magnetic imprint of today’s magnetic field, not the magnetic field of millions of years ago when the rock was originally formed,” said Knight.

Because of the movement of continents, magnetic north for the newly formed rock will be different from that of the older rock around it.

The researchers challenge the assumption that mountains are passive and that change occurs very slowly over long periods of time.

“Many people have considered mountains to be pretty passive agents, just sitting there to be affected by cold climates over these long periods of time.

“This evidence suggests that that is completely wrong. African mountain landscapes sometimes evolve very quickly and very dramatically over short periods of time. These are actually very sensitive environments and we need to know more about them,” said Knight.

The research was published in the Geomorphology journal and may hold important clues for the people living in the valleys below mountain ranges.

Source:  News24.com

 

 

Mountains not stable

13 Responses to Mountains not as stable, Wits researchers prove

  1. Ebert Oct 15, 2013 at 6:29 pm #

    FML this just shows the level of education accepted in this country. As a geology student I find this article a joke.

    —Firstly saying that this is new evidence… fail

    —“use a compass to prove” – every scientist knows you cannot prove anything, only disproving is accepted

    —couldn’t they find more advanced technology than a compass?

    —“A compass needle always points to magnetic north” – then why was it pointing at the phenomenon?!

    —There is enough iron containing minerals in some rocks that even felt fires can cause this phenomenon discussed above

    —As mentioned above, basalt contains iron, this means that oxidation will cause rapid weathering,the mountains were never stable and lightning wasnt the reason

    —As mentioned above, the rock is partially melted, two things, when it solidifies it should theoretically be stronger and partially means that there were still magnetic traces left from the old days. This implies that the old magnetic signature is still available

    —Any geologist can tell you not to base evidence on rocks on the surface, they are affected by conditions too much, so nobody would just measure the magnetic signature on the surface if they actually wanted to prove something.

    “The researchers challenge the assumption that mountains are passive and that change occurs very slowly over long periods of time.”
    Studying the vegetation on the mountain would provide more evidence to support this argument as some magnetic rocks aren’t going to affect the weathering as drastically as made to be. Let alone the rocks that would form after partial melting would most likely “out live” any of the rocks around it as it now contains concentrated iron.

    I dont even see how their evidence supports their conclusion: “Mountains not stable”?!

    Geological time vs. Human time
    (a continent colliding into another continent vs one factor of weathering)

    EPIC FAIL

    “The research was published in the Geomorphology journal and may hold important clues for the people living in the valleys below mountain ranges.” What clues? TELL ME

    THINK I’M TROLLING? read the source, now that’s a laugh

    eT

  2. Hendrik Oct 15, 2013 at 9:45 pm #

    Ja Ebert, I would like to see a bit more proof than just paleomagnetism. If they claim angular features are a result of, what they seem to imply, the change in the texture and fabric of the rock due to partial melting and recrystallisation, I would like to see some petrographic proof of this. That lightning bolt has to produce a significant amount of heat to partially melt a basalt, even with the low pressure at the surface and even when weathered. The scale of such a event would also be very small and I would like to think highly unlikely to have more than an extremely localised effect? Most of the drakensberg basalts are deeply weathered already so I think a simple structural interpretation looking at joints and faults on a large scale could shed some light on whether there is any basis for their findings or whether the angular features observed are just a result of preexisting structures.

    I would like to believe that a peer reviewed journal such as Geomorphology would ask for some more data than just paleomagnetics.

    I would still like to know what difference this makes in the stability of the mountains? South Africa is mostly very stable tectonically with only a few faults and minor shears active and only on a small and very localised scale(Augrabies, Wits). We only have a few minor earthquakes a year.

    I think some folks from the geoscience’s will shoot this research down soon enough.

  3. Hendrik Oct 15, 2013 at 10:05 pm #

    Link to the location of the actual paper. Even though I could only read the abstract and see some figures, it does not seem convincing

    http://www.sciencedirect.com/science/article/pii/S0169555X13003929

  4. ATheron Oct 15, 2013 at 10:06 pm #

    The comments are sad. How evolution fell into that thread I don’t wanne know…

    The News24 article is definitely a joke. But what more can you expect from News24?
    You are questioning the news article+the journal article. Go read the source of the source. Here’s an overview of your answers based on the actual paper since some of them question the science:
    “Lightning as a geomorphic agent on mountain summits: Evidence from southern Africa (2013) Jasper Knight, Stefan W. Grab.

    -I am unaware of a study that differentiates lighting and climate that has been done on the high berg, so technically it is new evidence.

    -Yes. (Disproving might have the same problems as proving). News24’s fault, not scientists. In the paper they use the term argue.

    -The compass was not their main determinant of lighting strikes. They used “geomorphology, rock surface hardness and induced magnetisation.”
    Although according to the geological survey bulletin 1083, page 132, “Anomalous remnant magnetization is so strong that it can be detected with a compass”

    -It points to the strongest local magnetic current, generally magnetic north. The researches use a shift in bearing as they move over the rock as evidence of re-magnetization. Geomagnetic research was not the point of the study as the Authors state.”

    -Felt fires should do it equally over the surface then and a spike can still be regarded as evidence? I am not a geophysicist, so can’t say.

    -Oxidation weathering is present, but cannot explain the clear physical weathering processes.
    -“Lightning wasn’t the reason” Support that statement. This paper suggests it is.

    -“Mountains where never stable” Exactly. That I believe is the main problem that News24 has. The authors don’t claim it to be. The paper aims to determine if lightning plays a role in the generation of summit debris that could be misread as resulting from climatic drivers(Frost-thaw etc). Debris has been used as indicators of past climates and if lighting did play a role it can change current views. There is quite some debate about Quaternary periglacial environments on the Berg, so I would see this research as useful.

    -The rock hardness inside the cracks where harder. That could make it more resistant to chemical weathering but the total rock now has a greater surface to volume ratio then before, leading to higher weathering rates. Also. There’s now more smaller rocks.

    -The old magnetic signature might be available, but was not the point of the study.

    -The goal was lighting, since it only hits the surface, why would you investigate deeper bedrock? Also magnetic fields deep within can be measured on the surface.

    -Any Geomorphologists will tell you that that they use the surfaces of rock as evidence, because it is often what the rocks are exposed to that is being investigated, not the underlying geology. This is a geomorphological article.
    Some background: Grab is one of the SA scientists that does research into paleoclimates, angular debris can be used as evidence for frost action or peri-glacial environments. Therefore it is the “Surface conditions” that are interesting. Not the geology.

    -No one said the magnetic rocks affect the weathering, you are missing the point, which is: Lightning as a geomorphic agent. I don’t know how studying the vegetation will prove much in this case.

    -Remember the rocks are now smaller, with more exposed surface. And if the Iron concentration goes up then oxidation weathering should speed up?

    -Their conclusion was not “Mountains not stable”. It was that lighting can cause similar weathering than climate action, that lighting debris are readily distinguishable, and that climate inferences must be made critically.

    -Understanding mountain sediment yield might be important :)

    Anyways: I’am waiting for comments on the paper from some of the other guys in SA Geomorphology, this paper claims alot…

  5. henkg Oct 15, 2013 at 11:39 pm #

    Phew! You Google anything and you get two, three opposing opinions. Good going guys. Now where is my rope…

  6. Hendrik Oct 16, 2013 at 12:48 am #

    Might want to point out my ‘opinion’ is based on my limited experience in the field. I read what I could of the paper and that combined with my own knowledge of the subject is why I am still sceptical of their findings and the science behind it.

    @henkg. You raise a good point. Many people google a topic and now they are experts…the rest of us go and study the subject in detail and work in the field to become experts.

    I am all for helping you find your rope, as long as it is 2 half ropes and not a sport rope ;)

  7. Justin Lawson Oct 16, 2013 at 7:05 am #

    Here is another one for you Ebert :)

    http://www.news24.com/Green/News/Mountains-shaped-by-lightning-20131015

    • Deon Oct 16, 2013 at 8:28 am #

      Note: Don’t take anything you read on news24 seriously!

  8. Ebert Oct 17, 2013 at 12:13 am #

    Opinions are always subjective to what you have learned. Hendrik I fully agree. Justin, why do you post articles like this? (not asked in an offending manner)

    eT

    • Justin Lawson Oct 17, 2013 at 7:13 am #

      Only to irritate you Ebert ;)
      But seriously, if something is mountain related I will generally post it up. Personally I find the geology of the mountains that we climb interesting.

      It’s also interesting to hear the opinions of others (especially of persons who are in the know).

      • Bruce Tomalin Oct 17, 2013 at 9:41 am #

        Yes please keep them coming Justin. I also found the discussion very interesting – thanks for starting it Ebert.
        And, Ebert, great that you are studying geology – would be cool if you could write some articles on geology for us from a climbing perspective. Kind of small scale stuff: like what are those funny round holes (pockets) caused by at Swinburne, why does the dolerite on top of some of the Free state koppies (eg Mooihoek at Everest) form vertical cracks. Interesting things to ponder while you’re wondering if your WC nuts are going to hold or not…

        • Ebert Oct 17, 2013 at 9:58 am #

          Cool, My knowledge is still very limited in the field as I’m merely a 3rd year student that reads articles when they seem interesting or articles that have new thoughts on earth’s evolution. \

          Bruce, post some photos or write an article on the location you want know about, let justin post it then I’m sure we can have some fun:) I’d have to see these places again before I start commenting:)

          eT
          I love this planet we call earth:D

Leave a Comment/Reply/Review