From the University of the Witwatersrand
New evidence on lightning strikes By Kanina Foss
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, and proving that mountains are a lot less stable than we think.
Image: fir0002 | flagstaffotos.com.au
In a world where mountains are crucial to food security and water supply, this has vast implications, especially in the context of climate change.
Professors Jasper Knight and Stefan Grab from the School of Geography, Archaeology and Environmental Studies at Wits University used a compass to prove – for the first time ever – 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. 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,” says Knight.
If you pass a compass over an area where a lightning strike occurred, the needle will suddenly swing through 360 degrees.
“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,” says 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. “You have two superimposed geomagnetic signatures. It’s a very useful indicator for identifying the precise location of where the lightning struck.”
Knight and Grab mapped out the distribution of lightning strikes in the Drakensburg and discovered that lightning significantly controls the evolution of the mountain landscapes because it helps to shape the summit areas – the highest areas – with this blasting effect.
Image: Professor Jasper Knight
Previously, angular debris was assumed to have been created by changes typical of cold, periglacial environments, such as fracturing due to frost. Water enters cracks in rocks and when it freezes, it expands, causing the rocks to split apart.
Knight and Grab are challenging centuries old assumptions about what causes mountains to change shape. “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.”
It is also useful to try and quantify how much debris is moved by these blasts which can cause boulders weighing several tonnes to move tens of metres.
“We can identify where the angular, broken up material has come from, trace it back to source, and determine the direction and extent to which the debris has been blasted on either side. Of course we know from the South African Weather Service how many strikes hit the land’s surface, so we can estimate how much volume is moved per square kilometre per year on average,” says Knight.
The stability of the land’s surface has important implications for the people living in the valleys below the mountain. “If we have lots of debris being generated it’s going to flow down slope and this is associated with hazards such as landslides,” said Knight.
Mountains are also inextricably linked to food security and water supply. In Lesotho, a country crucial to South Africa’s water supply, food shortages are leading to overgrazing, exposing the rock surface and making mountain landscapes even more vulnerable to weathering by lightning and other processes.
Knight hopes that this new research will help to put in place monitoring and mitigation to try and counteract some of the effects. “The more we increase our understanding, the more we are able to do something about it.”
A research paper to be published in the scientific journal, Geomorphology, is available here.
“george e. smith says:
October 15, 2013 at 10:21 am
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So do all mountains need lightning arrestor rods ? Just what remedial action do they suggest?”
Hmmm…could be a good use for all those extra bird-choppers that aren’t doing anything
useful elsewhere…..or perhaps they could find a way to store the energy from the lightning…
If nothing else, there would certainly be some entertaining YouTube videos coming out of this…
more money needed indeed….
The only place I have seen my compass go whacky is near a banded iron formation in central Ontario, which is a little disconcerting when your in the bush on a cloudy day.
@ur momisugly Latitude –
Thanks for the laugh.
What’s amazing is that the mountains could even exist to start with considering all the devastation they endure from electrical storms. The land scape should be on a global scale…totally flattened by so much lightening stone throwing. My leg is feeling stretched! 🙂
So, they will have to put lightning rods on the windmills in Africa, since building coal plants is not allowed (per World Bank rejection of financing them).
Problem solved, the misery continues. Next!
There is another little understood source of erosion, it is due to stupid geography professors walking all over fragile alpine tundra which takes decades to recover from the damage caused by their trampling on the fragile plants. We need to study this process and understand why stupid geography professors think we “need to do something” about a completely natural process that has been shaping our plant for eons.
What is next trying to do something about the sunrise??
/endsarc
Yes lightning can change rocks at the summit of high mountains, it can heat spall the rocks blasting off flakes and in certain circumstances it can split and violently move large rocks if its ground currents pass through a crack filled with water causing a steam explosion.
This is well known to folks who spend time in the mountains. Maybe the professor should get out more and learn from people who have spent some time in the mountains.
I wonder how many hours they spent wandering lost in the Drakensburg before they realized that the lightning pixies were affecting their compasses?
With all the $$$,$$$,$$$,$$$.$$ wasted on CAGW we could have purchased the entire African continent. Between the EPA, DOE, et al, just think how much better off the planet would be. !!!
Save the mountains!
Doug Huffman, the article and your mountaintop storm experience reminded me of this. REO Speedwagon – Ridin’ The Storm Out:
Aside from the silliness of the article this has given me something to think about. I have climbed many of the 14teeners and often wondered about the rubble {on top} of the peaks. While it is easy to see how areas below long gone glaciers were filled with rock pulled from the sides by ice leverage, and certainly beneath rock faces where freeze thaw cycles break off rock, it was difficult to imagine how the piles of rubble on the peaks was formed. I think I will make it a point to go to a peak right after a lightening storm, that would be the next morning, and look for evidence of the lightening strikes. Interesting concept. Thanks WUWT!
JohnS says:
October 15, 2013 at 10:33 am
I agree with you.
Based on the abstract all they appear to be saying is that … to make uncritical climatic inferences based on the presence of ‘frost shattered debris’ on mountain summits is wholly erroneous …
It could have been lightning that shattered the debris not sub-freezing temperatures.
A wholly reasonable statement.
So what !!!!
I have a “sniff test” problem with this. The planet has had mountains (volcanic and non-volcanic, on land and sea-mounts) for what must be most of its 4 billion-odd years – from when it cooled from the original molten mass. And unless the laws of physics have changed it has had lightning strikes for as long as it has had oceans and an oxygenic atmosphere, so perhaps for 2 billion years.
So the lightning-strike blasting/erosion must have been going on for hundreds of millions of years –and there are still plenty of mountains out there. And the only way mountains are “crucial to food security and water supply” is through reduced glacier or winter snow/ice melt restricting water supplies – so this is all really just another “climate change” sales pitch/scare story.
Personally I think the mountains are far more likely to be eroded by the boots of all the humans now tramping over them!
Show me the fulgurites!
There one thing lightning can do easily that freeze-thaw cycles cannot do, and that is to MELT rock. Show me the shattered mount tops covered with fulgurites and I will consider your case.
WOW!! AS stated above, where to even begin with this nonsense? Let’s start here: The rock they are talking about, the Drakensburg basalt, is a generally typical Mid-Ocean Ridge Basalt (MORB) extruded onto a sedimentary basin. I have worked in MORB terrains my entire career – in fact, I grew up and did all of my education, apprenticeship and a LOT of my professional career measuring brittle deformational structures in MORB terrains.
You simply can NOT measure remnant paleomagnetism in the field with a compass – and I use the finest, most sensitive compasses you can get. Of the thousands (literally) of measurements I have made personally in MORB terrains I have never once had an errant reading caused by magnetic interference – I know because I have mapped structures across the contacts with sedimentary rocks in the exact same geologic setting being described by these characters and I get consistent results regardless of which formation I am in.
This is just incoherent rubbish.
Second – when something like lightening fuses one usually ends up with a glass (obsidian) because the quench time is so brief. In an obsidian (or any glass) there is no time for minerals to form, even on the microscopic scale – obsidian is an amorphous silicate solid with no internal mineralic order. What these authors are proposing is a process which takes a LONG time to form in rocks; e.g. a basalt flow might take hundreds to thousands of years to solidify, at the end of which the rock is basalt, which is fine-grained rock in which there was insufficient cooling time for larger crystals to grow. Remnant magnetism is recordable in such rocks but not by a hand-held compass. The point is, obsidian does NOT record remnant magnetism because minerals, which take years to re-form after fusion, are the loci of the iron and minerals are not present. The iron is present WITHIN the mineral structure (FeSiO4, Olivine; orthopyroxene, [Mg,Fe]SiO3; clinopyroxene, CaMgSi2O6 – CaFeSi2O6; amphiboles, Fe7Si8O22(OH)2 (using the most iron rich) and does not occur as free iron in the rock. When melted by something like lightening, re-solidification is too rapid for the formation of minerals, especially with a magnetic signature large enough and strong enough to be measured with a pocket compass.
This is preposterous and an absolute shame. I am truly embarrassed for those two. It’s their own fault, of course, but it is embarrassing all the same.
Are we entering a new era of pseudo-science?
“This is preposterous and an absolute shame. I am truly embarrassed for those two. It’s their own fault, of course, but it is embarrassing all the same.”
The real problem is people like that are not embarrassed. Seems to be the norm these days. Or at least more obvious.
Drakensburg, Drakensberg, Dragons Mountain, Smaugs Lair.
This is thunderbolts.info
(Just some sort of joke)
tadchem says:
October 15, 2013 at 11:51 am
I have a box full of fulgurites that I collected from a sand dune. They are amazingly complex tubes of fused “glass” that are smooth and shiny on the inside and granular sand castings on the out side. I have seen fulgurites made of coarse gravel matrix. The dictionary definition states: “A tube like formation in sand or ROCK, caused by lightning. ”
Tell me again how lightning is generated? “We don’t know.” It is just extremely energy dense.
C’mon, now- y’all should know better than to give the authors such a hard time for this. How are they gonna get another grant if they don’t link to climate change? The authors are only trying to get more funding, sheesh.
/ << sarc tag
“Personally I think the mountains are far more likely to be eroded by the boots of all the humans now tramping over them!”
Now you could actually measure in a lab the typical Hi-Tech or other sole grinding away on granite or otherwise. I think the boots lose. Or just look at the surface of a well travel sidewalk…
Last time I looked I didn’t see much foot traffic on those mountains I fly over…I’ll take a closer look and take pictures of the grinding process. Actually, Google has fairly good pictures of mountain tops…let’s see now…hhmmm…not much change…
🙂
In my aerial firefighting days I was based a Winslow Az. One of the locals, a Navajo guy Named
Jonas Red Deer, had quite a collection of lighting generated glass tubules got them on Mesas
,high desert, etc. No that these ah, “Scientists”. would actually stoop to talking to a local about
obvious,, local conditions that have been going on for oh, millennia …
This smells of grant money- or at least something green.
tgmccoy: No that these ah, “Scientists”. would actually stoop to talking to a local about
Actually, those things have a name — fulgurites. There’s even a Wikipedia article http://en.wikipedia.org/wiki/Fulgurite
It’s an interesting article, but I wonder if the case isn’t a bit overstated. I would point out that it’s not uncommon for mountains to have research stations, radio transmitters, ski lift terminations, etc at or near the top. I’d think that if the mountains were being rapidly eaten by electrical discharge, someone would notice. I’d also point out that the highest rock in my part of the world — Mt Washington in NH (6288fr 1917m) has probably been around since North America slid over the Great Meteor hot spot about 100 million years ago. It can’t be eroding too quickly.or it wouldn’t be there.
The type of rock might matter. As I recall, Mt Washington is capped by Littleton Schist — a Devonian age marine clay or mudstone that has been thoroughly cooked until the various mineral components have melted and recrystallized.
Billy Liar: “It could have been lightning that shattered the debris not sub-freezing temperatures.”
This. The expansion of water shattering rocks is the same whether the expansion was from heat or cold. Seem obvious once you ask the question. Though I hardly know if any supposed controversy on the matter is about potential or degree. If potential, that should be disheartening; but what I’ve come to expect from expert researchers at large.