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Glaciers Protect Alpine Peaks From Erosion

Soulskill posted about a year ago | from the just-put-a-tarp-over-it dept.

Earth 29

Hugh Pickens DOT Com writes "BBC reports that French scientists studying erosion on Mont Blanc have discovered that glaciers shield summits from erosion, acting as a protective lid and playing little part in erosion. In contrast, water and rain eroded glacier-free areas 10 times faster than areas protected by the glacier. These results may explain the high altitude of the Alps. Driven by the tectonic collision of Europe with Africa, the high alpine bedrock is rising about one millimeter each year. Glacier-free areas of the Alps erode at a similar rate but where the mountains are protected by ice, the peaks wear away at one tenth that rate. A long-term effect of this might be a rise in the maximum altitude of the Alps. 'However, mountains don't grow to infinity, so there must be another mechanism which has lowered the summit of Europe,' says Fritz Schlunegger. 'According to (Dr) Godon's findings, this erosion is not related to glaciers, so we still have to think about other possibilities.' Around the globe, mountain glaciers — especially those at low latitudes — are retreating in response to climate change. The glaciers around Mount Everest have lost more than one-eighth of their area in the past 50 years, and the snowline had retreated 180 meters up the mountain sides. The results suggest that changes like these could change the shapes of the world's highest mountains, and that climate and mountain landscape are intimately linked."

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Surprising (3, Insightful)

timeOday (582209) | about a year ago | (#44466083)

I have always been told the jaggy, sawtooth peaks in glacier areas were caused by the continual cutting action of glaciers sliding downhill. (Then again, maybe that is still true, just 10x slower than being exposed to the elements).

Re:Surprising (4, Informative)

PPH (736903) | about a year ago | (#44466219)

Most of the weight of a glacier sits on the flanks of the mountain. That would be the area scrubbed by the movement of the glacier*. The ice/snow on the peaks is thinner and relatively stable. So the effect of a glacier-covered mountain is to have its flanks carved away, making it 'pointier'. This will continue until the slopes become so steep that the shape is no longer structurally stable. An ice-free mountain would probably erode uniformly from top to bottom and its resulting shape would be different (probably rounder on top).

*Increased melting rates causes glaciers to move faster, also accelerating the rate of mountain flank erosion.

Re:Surprising (1)

icebike (68054) | about a year ago | (#44466285)

Except you have lots of jaggy sawtooth peaks where there are NO glaciers [wikimedia.org] and U shaped valleys where there are glaciers [thinkquest.org] .

As for mountains eroding at a millimeter per, I'd like to know how they calculated that. If they simply measure the sediment in melt water and extrapolate that to cubit meters of rock and spread it over the entire watershed they would find that glaciated areas drop a lot more sediment [ingentaconnect.com] than non-glaciated areas.

On the other hand if they are doing actual height measurements, how do they arrive at that level of precision, or explain the fact that there is no visible or measurable sign of millimeter depth erosion on the tops of mountains?

Re:Surprising (0)

Anonymous Coward | about a year ago | (#44469037)

Why don't you ask them, instead of posting on a forum?

Re:Surprising (0)

Anonymous Coward | about a year ago | (#44469447)

Isn't YHVH the greatest engineer?
This whole complex system from quarks to the Universe working just like it's supposed to, in too good to be true fashion, seemingly defying the odds. Take away one aspect and the whole thing falls to shit and space dust. Random evolution my ass! Vegas wouldn't touch those odds, only self absorbed atheists are that comically stupid.

translation (0, Insightful)

Anonymous Coward | about a year ago | (#44466121)

We will need more govt grant money to study the effects of this.

Re:translation (-1, Flamebait)

pipatron (966506) | about a year ago | (#44466301)

I hope they don't get it! All the facts I need to know is in the BIBLE!

Re:translation (2, Funny)

Black Parrot (19622) | about a year ago | (#44466661)

I hope they don't get it! All the facts I need to know is in the BIBLE!

Driven by the tectonic collision of Europe with Africa, the high alpine bedrock is rising about one millimeter each year.

And now they're over six meters high!

Re:translation (1)

sycodon (149926) | about a year ago | (#44467955)

It was inevitable that a story which was actually kind of interesting and offered new insights would turn into some diatribe on global warming.

Seems like anytime anyone writes anything they just throw in some stupid reference to global warm to appear chic.

"Puppies and Kittens are cute and fun, but Global Warming threatens their fur"

Age of the glaciers (4, Insightful)

symbolset (646467) | about a year ago | (#44466129)

Most of the area of these glaciers is less than 13,000 years old. On the level of erosion of mountains, not significant. The glacier cover is quite new on this scale of time.

Re:Age of the glaciers (-1, Troll)

icebike (68054) | about a year ago | (#44466293)

Oh, but if we can pin yet another thing on global warming it will make it so much more scary.....

Re:Age of the glaciers (1)

swillden (191260) | about a year ago | (#44466395)

Most of the area of these glaciers is less than 13,000 years old. On the level of erosion of mountains, not significant. The glacier cover is quite new on this scale of time.

Just what I was going to say. The summary is conflating massively different time scales. Just because both of them are far longer than our lives doesn't mean they're the same.

Re:Age of the glaciers (1)

khallow (566160) | about a year ago | (#44467059)

Ok, the article says that peaks covered by glaciers eroded ten times as slow. If a peak is uncovered by interglacial periods a tenth of the time, then it still receives roughly just as much erosion from the interglacial periods as it does during the glacial periods and erodes about twice as fast as a mountain that is always covered by glaciers. That is significant on the time scale of millions of years.

Re:Age of the glaciers (1)

riverat1 (1048260) | about a year ago | (#44468075)

Most of the area of these glaciers is less than 13,000 years old.

I'm trying to understand where you get that statement from. Are you saying those areas were not glaciated during the last ice age (from ~100,000 years ago to ~13,000) years ago? I'm pretty sure they've had glaciers there during all of that time. It may be that the oldest ice in some of them is only 13,000 years old but that is simply a function of the fact that glaciers flow, they get new snow which becomes ice at the top and as it reaches the bottom it melts out.

13K years? What bible says that? (1)

dutchwhizzman (817898) | about a year ago | (#44468643)

Sorry to rain on your parade, but the mountains are way older than 13000 years. Maybe you are referring to the ice that's on them? There has been ice on them much longer as well. It's just the current layer of ice that isn't that old, due to the fact that it erodes and slides down the mountain. I doubt the age of the current bits of frozen water is relevant to how much it protects the mountain side from wind and sun erosion, it will be the fact that it's covered that matters.

Re:Age of the glaciers (1)

hawkfish (8978) | about a year ago | (#44491183)

Most of the area of these glaciers is less than 13,000 years old. On the level of erosion of mountains, not significant. The glacier cover is quite new on this scale of time.

Cite? Otherwise, I have no clue why this is modded +4 Insightful...

How do you get a baby to sleep (-1, Offtopic)

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Re:How do you get a baby to sleep (1)

Anonymous Coward | about a year ago | (#44466403)

A shot of brandy in the formula works well.

They've Got to be Kidding (1)

nukenerd (172703) | about a year ago | (#44466317)

FTFA - "Glacier-free areas of the Alps erode at a similar rate but where the mountains are protected by ice, the peaks wear away at one tenth that rate."

"Protected by ice" != "glacier"

Former glacial valleys, like in the UK looking down the A5 from Llyn Ogwen north-west towards Bethesda, are clearly far more eroded than the adjacent ridges. The valley is a huge U-shaped gouge, straight through the surrounding mountains,.

Re:They've Got to be Kidding (0)

Anonymous Coward | about a year ago | (#44466485)

That writeup is confusing. This is about peaks (and adjacent ridges) which aren't eroded by ice, because they obviously can't be. Ice can't flow over a peak, because it has no source above the peak.

Re:They've Got to be Kidding (1)

khallow (566160) | about a year ago | (#44467083)

Unless the ice happens to pile up above the peaks, which has happened to smaller mountains, but not to the Alps.

Mechanisms (0)

Anonymous Coward | about a year ago | (#44466409)

" there must be another mechanism which has lowered the summit of Europe,"

A couple of possibilities: During an ice age, when ice cover is in kilometres, the glacier could be wearing down the mountain tops if there is lateral movement of the ice. During a warm age there could be no ice but heavy rains that wear away the mountain tops.

Disclaimer: I am not a geologist. :)

Someone mod parent up. (1)

MickLinux (579158) | about a year ago | (#44467285)

I'd mod, but I want to reply.

One of the things that I love about the book of Genesis and Adam and Eve, is that it describes a unique geologic situation: A single river, in the mountains, that splits into four rivers while still in the mountains.

To me, that means that there had to have been significant glacial melting. That, in turn, means that there had to be significant temperature moderation. Looking at the region of Turkey [the four rivers seem to go around the Republic of Georgia, and kush -- not Ethiopia, but Western Turkey where there also was a Cush and a city kushdar -- and the Tigris and Euphrates], we see that Ararat has glaciers. But the "significant moderation of temperatures" would have occurred when the Black Sea filled. That, then, date stamps the story to be around, say, 5600 BC.

So glaciers form, and glaciers melt, and while they are there, they protect the surface. When they melt, they gouge the surface. Moreover, they don't have to melt entirely.

So, then, this just means that erosion of glaciated mountains is sporadic, not continuous.

Protective cap protects... (0)

Anonymous Coward | about a year ago | (#44466557)

News at eleven...

Really? This is news?

Will global warming (1)

tinfoilhatz (2809173) | about a year ago | (#44466897)

Cause the Alps to crumble away? Are humans to blame for destroying them?

Re:Will global warming (0)

delt0r (999393) | about a year ago | (#44469327)

Yes. The answer is always yes. Oh and we are all going to die.

Glaciers as Designed (0)

Anonymous Coward | about a year ago | (#44468003)

Sounds like the glaciers are behaving as they were designed: to eventually melt.

erosion is now unnatural ??? (0)

Anonymous Coward | about a year ago | (#44468675)

OMG OMG those mountains will be gone in 30 million years now !!!!

Remember that glaciers also carve out valleys in their flowdown the mountainsides. Slow but a great deal of force.

A Startling Find Indeed (0)

Anonymous Coward | about a year ago | (#44494159)

To hear Catastrophists like Prof. Richard Alley go on and on and on and on about the 'Glacier Buzzsaw' makes many in his audience emit buzzing sounds of snoring.

But a simple observation will endure.

Take the Himalaya-Karakorim and the St. Elias Mountains for example. Each occur along active tectonic plate boundaries. Subduction processes rule for the Himalaya-Karakorim Mountains and transpression-transtension processes for the the St. Elias Mountains. Both are geologically young, a few million years (we humans and forebears have existed for only much less than one millionth of time by comparison). And we find the Himalaya-Karakorim and St. Elias Mountains, the highest elevations on Earth are capped by perennial snow fields and glaciers. Where is Alley's 'Buzz Saw'? Answer: No where to be found! Alley is WRONG! The AGU and IPCC should stop listening to Prof. Alley and just look out their windows to witness reality. Else, people will say they are ... "Queer".

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