PRESSURE-MELTING OF ICE: While-U-Wait Bill Locke, Dept ...

PRESSURE-MELTING OF ICE: While-U-Wait
W. W. Locke, Dept of Earth Sciences, Montana State University, Bozeman, MT 59717; [email protected]
Theory

Practice
Requires:

Ice is weird!

Ice < Water Pressure drives solid ice liquid water Pressure-melting point (PMP) drops 0.7 C/ vertical km of ice Preparation: Melting point under 5-km thick Antarctic Ice Sheet -3.5 C http://www.chemistry.uvic.ca/codding/outline0124_files/image034.gif Fill bottle with water Make loop of wire to hang bottle on ice cube Arrange mount on table to suspend fork above pan Demo detail. Note wire resting on top of ice cube on fork. Demo setup Demo: Place ice cube (near room temperature) on fork Hang full bottle from ice cube by fine wire loop Ask students to pose multiple working hypotheses as to the likely outcome. Wait ~15 minutes while discussing principles (listed to the left) Most basal ice is at PMP Cant cool further because of thermal gradient Cant warm further because of ice; basal melting Result: Maximizes melt @ bed! Pressure-melting strongly affects basal ice processes http://gemini.oscs.montana.edu/~geol445/hyperglac/morphology1/ Wire cuts through ice cube (pressure melt) Ice refreezes behind it (regelation) Melting cube can be picked up and held by its end! A septum of bubble-free regelation ice marks the healed track. Demo half-complete. Note wire disappearing into middle of ice cube. Demo nearing completion. Note wire resting on fork edge, but not yet to the base of the (melting) ice cube. Discussion: Plucking = f(pressure-melt and regelation Abrasion = f(basal melt) downflow, returning clasts to the bed 2-liter soda bottle 32-guage rust-resistant craft wire Ice cube Mount (fork and C-clamp) Drainage collection pan Is ice too weak (100 kPa shear strength) to resist wire; if so, why did the ice heal? Does ice heal as refreezing because of residual cold from the freezer; if so, why did it melt at first? The actual stress can be calculated from wire diameter, ice cube width, and bottle weight. http://gemini.oscs.montana.edu/~geol445/hyperglac/systems1/ Demo finale. Note wire resting on fork and the ability to pick up the shrinking ice cube. Significance: Pressure-melt is a phenomenon that occurs at scales of time, space, and force that can readily be duplicated in the classroom it is of widespread importance beneath glaciers and ice sheets. Demo Grand Finale! Note that the ice cube, although smaller, is intact. Healed septum is barely visible.

Recently Viewed Presentations

• Unbiasedness. Unbiasedness: The expected value (mean) of the statistic is exactly equal to the value of the parameter being estimated. The sample mean is an unbiased estimator of the population mean.
• to GM (£6bn p.a.) creates opportunity for push towards innovation. Health Innovation Manchester (HInM) provides platform to focus priorities around system and place. Synergies with digital sector support drive towards globally leading centre for . clinical trials.
• Economy Travel. Also includes transfers to and from Airports. Tour, Travel, & Hotel Groups. Students will be broken up into tour groups. These tour groups can be across disciplines. ... Travel from Rome to Pompeii for a guided tour. Lunch...
• Shape is of paramount importance: groups of a same kind may replace each other if they are shaped likely BioIsoSteres - Equivalent Functional Groups Wikipedia: bioisosteres are substituents or groups with similar physical or chemical properties that impart similar biological...
• PMI Sydney Chapter is a non-for-profit organisation whose mission is to serve you - our valued member - as well as support the promotion and advancement of the art, science and benefits of portfolio, program & project management. ...
• Data Warehousing Overview: Issues, Terminology, Products and Research Author: Janet Wiener Last modified by: Ruoming Jin Created Date: 6/13/1997 9:22:38 PM Document presentation format: On-screen Show (4:3) Other titles
• k is Boltzmanns constant 1.38*10^-23 joules/ kelvin. Where does EMECalc get Tsys and Antenna gain from? And what is Tsys? System Noise Temperature, Tsys, definition. Tsys = Trx + Tsky + Tspill +Tft. Trx. Receiver noise temperature contribution from line...
• Chemistry Atomic Structure * John Dalton had ideas about the existence of atoms about 200 years ago but only relatively recently have special microscopes (called electron microscopes) been invented that can 'see' atoms Acknowledgment The image is a false-colour high-resolution...