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Author Topic: What makes these rocks move?  (Read 3753 times)

Offline thedoc

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What makes these rocks move?
« on: 22/02/2011 18:08:57 »
Mysterious moving stones in a Death Vally lake bed may have been solved.

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« Last Edit: 22/02/2011 18:08:57 by _system »


 

Offline RD

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What makes these rocks move?
« Reply #1 on: 22/02/2011 20:21:58 »


If they are moved by the wind how can neighbouring stones travel in different directions ?

Alternative no-wind hypotheses here
« Last Edit: 22/02/2011 21:51:47 by RD »
 

Offline Bass

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What makes these rocks move?
« Reply #2 on: 23/02/2011 00:16:41 »
Having been to racetrack lake (playa) and seen the tracks, they seem to defy explanation.  Some of the tracks are hundreds of meters long, others only a few meters.  All different sizes and shapes of rocks "sail" across the playa.  And RD is right, the tracks do cross each other.  one other thing, the wind does blow there, ferociously at times.  The wind has always blown when I've been in Death Valley (mostly in winter months), sometimes so forcibly that it's hard to stand.  As my partner once said, as a gust almost sent our truck into the ditch, "The wind doesn't blow here, it sucks"

I believe wind is the motive force- but I also agree that you need sufficient water and freeze-thaw cycles to reduce friction to the point that the wind can move these boulders.  Who knows- maybe these are really wind depression valleys instead of fault blocks??
 

Offline RD

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What makes these rocks move?
« Reply #3 on: 23/02/2011 08:48:48 »
Who knows- maybe these are really wind depression valleys ...

Like a vortex street behind the stone ?


http://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_vortex_street

However the stones are reported to have moved, not just developed trails.

Say a stone was raised up when the wet ground froze (ice expands) and when it thawed the stone sat back down again and a little mud under the stone was expelled in this process. If mud under the stone was not expelled symmetrically during the thaw, (say due to ridges on the underside of the stone), that asymmetry could propel the stone horizontally, (very slowly).
« Last Edit: 23/02/2011 09:09:36 by RD »
 

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What makes these rocks move?
« Reply #3 on: 23/02/2011 08:48:48 »

 

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