Topic: Drifting "Ice Island" iceberg could pose threat to ships, oil rigs off Canada

[George Wallace]

Glass is an amorphous solid.

There is a fundamental structural divide between amorphous solids (including glasses) and crystalline solids (the solids we would think about (steel etc...) . Structurally, glasses are similar to liquids, but are not in fact.

I stand corrected.  However, glass like liquids does flow................at an extraordinarily slow rate, as witnessed in very old glass windows (very old - 100 years or more).

I linked the above "amorphous solid" to a FACT page.

[PPCLI Guy]

You're right, just tried it and nothing happened. The rise I was seeing before was from thermal expansion after the ice had melted. After doing some reading water is one of the few things denser when it's a liquid then when it's a solid. So ya a claim of 6m is ridiculous to say the least.

You do know that the Greenland ice shelf is actually NOT in the water per se right now, right?  A better experiment would be to watch the water level in your glass as you ADD ice cubes.

[Kat Stevens]

I work with water all the time.  It's about the only substance I know of that expands when both heated and frozen, and can't be compressed.

[ArmyVern]

You do know that the Greenland ice shelf is actually NOT in the water per se right now, right?  A better experiment would be to watch the water level in your glass as you ADD ice cubes.

I'll have to add more rum to make up for that variable. 

[George Wallace]

From the Australian Government Environment Ministry:


 FACTS ABOUT SEA LEVEL RISE

Are reports of sea level rise of 6m correct?
With recent observations of the speed-up of some glaciers in both Greenland and Antarctica, it has been argued that the IPCC estimate of the ice dynamic effect may be too low. Total sea level rise of as much as 6 m over the next century has been proposed based on a comparison with sea level rise rates at the end of the last ice age.

However, at the end of last ice age there was three times as much ice to melt as there is presently on the Earth. A rise of sea level by 6 m over the next century is improbable within constraints of the area of present day ice sheets, and the rate at which glaciers can accelerate.

A more generally accepted upper bound of sea level rise over the next century is 2 m. The probable rise will be less than this, although possibly toward the upper end of the IPCC AR4 estimate of around 0.8 m.

[Chunks]

The problem is not the ice in the water, the problem is the melting ice on land. Antarctica and Groenland being land, the ice contained on their surface is not taken into consideration for the sea level until it actually melt.

As for Halifax, research has shown that the sea level has been rising by 3.2 mm/year since 1920 and projection for the future using  recognized model shows that the sea level might rise to 0,73 m average in the next century with maximum sea level up to 1,3m. Until now, most projection underestimated the rate of climate change so we can probably ballpark at 1m if not more.

http://www.halifax.ca/regionalplanning/documents/HRM-OF_v5.pdf

and here's a presentation given to the HRM municipal council on Feb 2009.
http://www.halifax.ca/council/agendasc/documents/100209cow4.pdf

Of course you can argue about climate change and the reasons for rising sea levels but you can't really argue with the fact the sea level is actually rising, that the rate is increasing  and that in a distant future, Lower water street will pretty much be underwater.

Enjoy the Lower Deck while it's still there 

[Jaybar]

You do know that the Greenland ice shelf is actually NOT in the water per se right now, right?  A better experiment would be to watch the water level in your glass as you ADD ice cubes.

Of course I do. The problem is that this article reads like some doomsday warning "Ice is melting, we're all going to die"! Even if all of the ice sheet on Greenland melted it would take hundreds to thousands of years for that to happen. Unless something really bad happens in which case I think the ice melting is going to be the last of our worries.

This is one of the better reports I could find on climate change:

http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/

[HavokFour]

Ladies and gentlemen, nature can be a mean mistress.  I propose everyone on the planet open their fridges and freezers simultaneously to combat her. But really, it's just a bit of water.

Thank god my parents had the foresight to send me to swimming lessons when I was a kid.

[George Wallace]

From the Australian Government Environment Ministry:


 FACTS ABOUT SEA LEVEL RISE


If you follow the above link you can visualize using the diagrams, charts and data supplied what their research has concluded.

[ArmyVern]

Oh yeah, for all those wondering - I have discovered that watching ice melt is indeed worse than watching bread toast, even given the rum & cokes that I drank while supervising the experiment.

- Not an iota of movement in the liquid level up or down for the ice cubes that were already ìn the glass. However, that all changed when I added more ice cubes to the liquid then watched a sudden increase occur (as if the ice cubes were sliding into the glass from 'land') ... I then had to drink quickly to reduce liquid level - lest I overflowed.

Will re-do tonight and see if I obtain same results.

[PMedMoe]

IIRC, ice melts at the same rate as water evaporates, so there should be no difference in the level after the ice melts.

[recceguy]

My feet aren't wet, I don't care.

This is starting to get just a little retarded.

[N. McKay]

Fact for you Trivial Pursuit buffs:  Glass is a liquid.

Everything you said was right up to this point.  It's been repeated often, but glass isn't really a liquid.

Back to the ice, the level of the sea changes when the piece of ice falls in, not when it melts.  Ice is less dense than liquid water, so a given volume of water produces slightly more ice (which sticks up above the surface when the ice is floating).  When the ice melts it returns to the density of liquid water so the surface stays exactly where it is.  Evaporation doesn't play any part in it.

Water is unusual in this behaviour.  For most materials the solid does tend to be denser than the liquid (and much denser than the gas).  As you cool water it does become denser, but only until you reach about 4 degrees Celsius.  As it cools below that temperature (and eventually freezes) it expands.  That's why frozen pipes burst.

[Nerf herder]

This sums it all up nicely:

http://www.phys.ncku.edu.tw/mirrors/physicsfaq/General/Glass/glass.html

There have been many claims (especially by tour guides) that such glass is deformed because the glass has flowed slowly over the centuries.  This has become a persistent myth, but close inspection shows that characteristic signs of flow, such as flowing around, and out of the frame, are not present.  The deformations are more consistent with imperfections of the methods used to make panes of glass at the time.  In some cases gaps appear between glass panes and their frames, but this is due to deformations in the lead framework rather than the glass.  Other examples of rippling in windows of old homes can be accounted for because the glass was imperfectly flattened by rolling before the float glass process came into use.

It is difficult to verify with absolute certainty that no examples of glass flow exist, because there are almost always no records of the original state.  In rare cases stained glass windows are found to contain lead, which would lower the viscosity and make them heavier.  Could these examples deform under their own weight?  Only careful study and analysis can answer this question.  Robert Brill of the Corning glass museum has been studying antique glass for over 30 years.  He has examined many examples of glass from old buildings, measuring their material properties and chemical composition.  He has taken a special interest in the glass flow myth and has always looked for evidence for and against.  In his opinion, the notion that glass in Mediaeval stained glass windows has flowed over the centuries is untrue and, he says, examples of sagging and ripples in old windows are also most likely physical characteristics resulting from the manufacturing process.  Other experts who have made similar studies agree.  Theoretical analysis based on measured glass viscosities shows that glass should not deform significantly even over many centuries, and a clear link is found between types of deformation in the glass and the way it was produced.

There is no clear answer to the question "Is glass solid or liquid?".  In terms of molecular dynamics and thermodynamics it is possible to justify various different views that it is a highly viscous liquid, an amorphous solid, or simply that glass is another state of matter that is neither liquid nor solid.  The difference is semantic.  In terms of its material properties we can do little better.  There is no clear definition of the distinction between solids and highly viscous liquids.  All such phases or states of matter are idealisations of real material properties.  Nevertheless, from a more common sense point of view, glass should be considered a solid since it is rigid according to everyday experience.  The use of the term "supercooled liquid" to describe glass still persists, but is considered by many to be an unfortunate misnomer that should be avoided.  In any case, claims that glass panes in old windows have deformed due to glass flow have never been substantiated.  Examples of Roman glassware and calculations based on measurements of glass visco-properties indicate that these claims cannot be true.  The observed features are more easily explained as a result of the imperfect methods used to make glass window panes before the float glass process was invented.

[George Wallace]

Everything you said was right up to this point.  It's been repeated often, but glass isn't really a liquid.

 

Glass is an amorphous solid.

There is a fundamental structural divide between amorphous solids (including glasses) and crystalline solids (the solids we would think about (steel etc...) . Structurally, glasses are similar to liquids, but are not in fact.

I stand corrected.  However, glass like liquids does flow................at an extraordinarily slow rate, as witnessed in very old glass windows (very old - 100 years or more).

I linked the above "amorphous solid" to a FACT page.

But thanks for pointing it out again.


As Quag also pointed out to me, and Der Panzerkommandant has posted, the fact of the affects of gravity on glass has also been proven by some as being a myth.