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Ice rafts not sails: Floating the rocks at Racetrack Playa, Paper by Ralph Lorenz et. al.
ngunn
post Dec 29 2010, 06:04 PM
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Thanks once again to Jason B for making this intriguing paper accessible to all: http://barnesos.net/publications/papers/20...track.Rafts.pdf
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ElkGroveDan
post Dec 29 2010, 07:14 PM
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I suppose others have already thought of solar powered web cams and things like that. Though it seems that we are looking at movement during periods of partial immersion where the rocks may be barely visible from above.


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rlorenz
post Dec 29 2010, 10:44 PM
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QUOTE (ElkGroveDan @ Dec 29 2010, 02:14 PM) *
I suppose others have already thought of solar powered web cams and things like that.


yes.

Took a long time to get a permit but it can be done subject to certain Parks Service
limitations.

Since winter is the time of interest, and cameras cannot be left on the nice flat playa
itself, solar power is less effective than it might be, but digital timelapse cameras can
run on alkaline Ds for months.
http://www.lpl.arizona.edu/~rlorenz/timelapse.pdf

One would have to be very lucky to see the rocks move, but timelapse has been proving
useful to understand the conditions on the playa (how often flooded, how often frozen etc.)
That work is being written up right now.

btw, I believe someone has been doing Gigapan surveys of the playa for a year or so. I
tried a Gigapan myself but it drained the batteries in minutes and was overall rather
frustrating.
Having been going to the playa a couple of times a year since 2006, I've found walking
around and doing manual pans from GPS-fixed locations to be a very time-efficient means of
survey. Just wish the bastard rocks would actually move.
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ElkGroveDan
post Dec 30 2010, 12:21 AM
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Reading your paper Ralph it looks like the occurrence and duration of ice is still being debated. Have you though of getting permission to bury a couple of temperature sensors just below and/or at the surface of the soil to record long term temperature profiles? Also, have you tested the water seasonally for saline content?


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rlorenz
post Jan 12 2012, 05:10 AM
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QUOTE (ElkGroveDan @ Dec 29 2010, 07:21 PM) *
Reading your paper Ralph it looks like the occurrence and duration of ice is still being debated.


Indeed. I think much of the literature has been unfortunately cast in black-and-white terms
'Ice is essential'... 'Oh no it's not'...'oh yes it is' etc..... (qv Sharp and Carey, Reid et al., etc.)

The reality is likely more nuanced - my take is that large rocks require ice, and that for most large-scale
movements (i.e. when many rocks move) ice is involved. But small rocks can occasionally move
without the help of ice sails (or more particularly, ice rafts). I suspect too that there is a spatial
element to it - the south end of the playa where most of the rocks are delivered to the playa
surface from the cliffs is also probably the area most often shadowed by same cliffs when the
sun is low in the sky in winter. So the south end is more likely to see ice than the north.

But all this is qualitative handwaving without quantitative data (as Kelvin sortof said). It may
be in part that the problem has mostly been studied by geologists, who as a tribe (this is fightin'
talk, I know) may be less inclined to apply probabilistic (or even quantitative) approaches
to the problem.

To remedy this deficiency, our efforts over the past few years at least now provide some
basis for discussion on occurrence and duration of water and ice on the playa. Also, while
it is all very well for someone to figure out that winds of X speed can move a rock of Y
mass without ice, there has really been only handwaving 'this is reasonable/not impossible' etc.
Can such winds occur often enough to explain the trails we see ?

Some actual numbers on how often gusts of 50 m/s actually occur (at least at nearby
locations) and how often is the playa flooded, are now published in Journal of Applied
Meteorology
http://www.lpl.arizona.edu/~rlorenz/racetrackweather.pdf
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Posts in this topic
- ngunn   Ice rafts not sails: Floating the rocks at Racetrack Playa   Dec 29 2010, 06:04 PM
- - ElkGroveDan   Fascinating paper Ralph. This is one of my favori...   Dec 29 2010, 06:18 PM
- - djellison   I must get up there and Gigapan the place. It...   Dec 29 2010, 07:11 PM
- - ElkGroveDan   I suppose others have already thought of solar pow...   Dec 29 2010, 07:14 PM
|- - rlorenz   QUOTE (ElkGroveDan @ Dec 29 2010, 02:14 P...   Dec 29 2010, 10:44 PM
|- - ElkGroveDan   Reading your paper Ralph it looks like the occurre...   Dec 30 2010, 12:21 AM
|- - rlorenz   QUOTE (ElkGroveDan @ Dec 29 2010, 07:21 P...   Dec 30 2010, 01:22 PM
|- - rlorenz   QUOTE (ElkGroveDan @ Dec 29 2010, 07:21 P...   Jan 12 2012, 05:10 AM
- - PDP8E   Ralph, Thank you for that fascinating paper! ...   Dec 30 2010, 08:29 PM
- - nprev   Real blue-sky suggestion here, but would putting l...   Dec 31 2010, 01:48 AM
|- - Juramike   QUOTE (nprev @ Dec 30 2010, 08:48 PM) rem...   Dec 31 2010, 01:43 PM
|- - rlorenz   QUOTE (nprev @ Dec 30 2010, 08:48 PM) Rea...   Dec 31 2010, 01:50 PM
|- - ZLD   QUOTE (nprev @ Dec 31 2010, 01:48 AM) Rea...   Dec 31 2010, 04:59 PM
- - Julius   i've just seen a programme on weird or what...   Dec 31 2010, 09:30 AM
- - nprev   Hmm. Got it, Ralph. Well, let's see: How abou...   Jan 1 2011, 09:44 PM
- - djellison   QUOTE (ZLD @ Dec 31 2010, 08:59 AM) I wou...   Jan 2 2011, 01:44 AM
- - ZLD   If that is out, then so is just about every other ...   Jan 2 2011, 09:09 AM
- - Floyd   Ralph, very nice paper. My niece works for the Na...   Jan 20 2011, 02:29 PM
- - Floyd   Well the rocks move slowly so it took a few years ...   Aug 27 2014, 10:28 PM
|- - rlorenz   QUOTE (Floyd @ Aug 27 2014, 06:28 PM) Wel...   Sep 1 2014, 12:05 AM
- - nprev   I remember first reading about this in 1973, and o...   Aug 28 2014, 04:19 AM


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