Page 1 of 8

Dynamic Planet B/C

Posted: August 4th, 2013, 3:01 pm
by Jim_R

Re: Dynamic Planet B/C

Posted: August 28th, 2013, 7:50 pm
by ScienceOlympian
Do you know if there are any major changes to this event?

Re: Dynamic Planet B/C

Posted: August 28th, 2013, 7:53 pm
by zyzzyva980
Chances are no, since the overall topic (Glaciers) remains the same.

Re: Dynamic Planet B/C

Posted: August 28th, 2013, 7:58 pm
by Skink
Even without rules in my hands, I can confidently say 'No.' The topic is glaciers for another season (wonderful), and the earth science committee (and this event, specifically, which is not intended to be solely rote memorization of glacial facts) is known for allowing resources, so I'd expect both the topics you can be tested on to primarily be the same save for some bolds here and there and the resources you can bring to still be more cheat sheets than you likely need :P . To that end, if you want to begin studying now, there's a wealth of information from last season to start with!

Re: Dynamic Planet B/C

Posted: August 28th, 2013, 8:25 pm
by geminicross
resources you can bring to still be more cheat sheets than you likely need
What I love about Dynamic Planet. :)
I had to find ways to fill my sheet one year.

Re: Dynamic Planet B/C

Posted: September 2nd, 2013, 9:40 am
by Crazy Puny Man
geminicross wrote:
resources you can bring to still be more cheat sheets than you likely need
What I love about Dynamic Planet. :)
I had to find ways to fill my sheet one year.
Yeah!

Jeez I could not find enough information to fill all 4 sheets. Almost all of them had some blank space on it -_-

Anyway, does anyone have any suggestions about resources for things like glacial history & specific glaciers/landforms? I mostly used Wikipedia for that, and it seemed a little...excessive? Seemed like way more than I needed, but I couldn't find anything that was much better, and I just wanted to know what resources other people were using for it

Re: Dynamic Planet B/C

Posted: September 10th, 2013, 4:40 pm
by PacificGoldenPlover
You mean you are not studying for pure love of the topic? :p
There are some pretty good glacier books on the market, different ones for different levels.

Re: Dynamic Planet B/C

Posted: September 11th, 2013, 5:17 pm
by Crazy Puny Man
The added space saves me a bit of stress, to be honest :P

...that still sounds pretty detailed to me. Worth a shot I suppose.

So that's where you got your information on surges from!

\me goes & edits last post

Re: Dynamic Planet B/C

Posted: September 11th, 2013, 6:23 pm
by PacificGoldenPlover
Crazy Puny Man wrote:Um...I'm not sure I follow you >_> The channels are in the middle of the glacier, i.e. not at the base, right? Also, wouldn't the meltwater travel to the base through moulins? Moulins are how supraglacial meltwater gets down to the base...

Are you saying that the meltwater, instead of traveling through tunnels in the ice, percolate/leak through the glacier and travel to the base? Or that the added stress simply increases pressure & therefore lowers the ice's melting point?
Well, essentially, water gets to the base both from subglacial (mainly R) channels and englacial channels.

Ironically, the more channelized subglacial flow is, the slower it goes compared to glaciers exhibiting subglacial meltwater sheet flow. R-Channels are narrow and cut upward into the glacier, and so, do not lubricate the entire bed. Sheet flow can be millimeters or less thick, but since it lifts most of the glacier up above the bed, it causes it to move faster. As such, when R-channels collapse to form sheet flow, they speed up the glacier.

You definitely do see some of both englacial channel flow and percolation in a glacier (there is a zone in the accumulation area called the percolation zone) this mostly occurs by water moving through the crystal lattice, or by flow through microscopic veins. Prior to a surge, however, channels in the bottom of a glacier essentially give way.

One little thought experiment about why sudden mass deposition does not really play a role in glaciers. A typical surging glacier may be anywhere from 800-1000 meters deep. So, if you doubled the mass on top of the glacier you would lower the pressure melting point by a lot, and possibly cause a surge. HOWEVER, snow from avalanche will be less than 1/10th the density of the glacial ice. And on top of which, there is essentially no way even the largest avalanches can cover the area of a glacier at an adequate depth to significantly change the pressure-melting point at the bottom. There may have been one or two exceptions, but it's generally just not the case.

Re: Dynamic Planet B/C

Posted: September 13th, 2013, 8:52 pm
by Crazy Puny Man
PacificGoldenPlover wrote:
Crazy Puny Man wrote:Um...I'm not sure I follow you >_> The channels are in the middle of the glacier, i.e. not at the base, right? Also, wouldn't the meltwater travel to the base through moulins? Moulins are how supraglacial meltwater gets down to the base...

Are you saying that the meltwater, instead of traveling through tunnels in the ice, percolate/leak through the glacier and travel to the base? Or that the added stress simply increases pressure & therefore lowers the ice's melting point?
Well, essentially, water gets to the base both from subglacial (mainly R) channels and englacial channels.

Ironically, the more channelized subglacial flow is, the slower it goes compared to glaciers exhibiting subglacial meltwater sheet flow. R-Channels are narrow and cut upward into the glacier, and so, do not lubricate the entire bed. Sheet flow can be millimeters or less thick, but since it lifts most of the glacier up above the bed, it causes it to move faster. As such, when R-channels collapse to form sheet flow, they speed up the glacier.

You definitely do see some of both englacial channel flow and percolation in a glacier (there is a zone in the accumulation area called the percolation zone) this mostly occurs by water moving through the crystal lattice, or by flow through microscopic veins. Prior to a surge, however, channels in the bottom of a glacier essentially give way.

One little thought experiment about why sudden mass deposition does not really play a role in glaciers. A typical surging glacier may be anywhere from 800-1000 meters deep. So, if you doubled the mass on top of the glacier you would lower the pressure melting point by a lot, and possibly cause a surge. HOWEVER, snow from avalanche will be less than 1/10th the density of the glacial ice. And on top of which, there is essentially no way even the largest avalanches can cover the area of a glacier at an adequate depth to significantly change the pressure-melting point at the bottom. There may have been one or two exceptions, but it's generally just not the case.
Gotcha, that makes more sense. The channels direct water away from the bed, not toward it.

Yeah, I understand now (both the thing about the R-channels & about why surges usually don't happen through avalanches) :oops:

Thanks for the help/info! :geek: