This topic has been archived, and won't accept reply postings.
I came across this definition of glacier ice - 'A mono-mineralic type of rock, composed of crystals of the mineral ice' here: http://pubs.usgs.gov/of/2004/1216/g/g.html
I've never heard it defined as such before. Assuming this definition is technically correct is it of any help in understanding the nature and properties of glacier ice or is it just a bit of an oddity?
I've never heard it defined as such before. Assuming this definition is technically correct is it of any help in understanding the nature and properties of glacier ice or is it just a bit of an oddity?
In reply to DaveHK:
Perfectly legit - e.g. we've seen ice boulders on other moons. It just sounds odd because we're used to living at temperatures and pressures where H2O is mostly liquid.
Perfectly legit - e.g. we've seen ice boulders on other moons. It just sounds odd because we're used to living at temperatures and pressures where H2O is mostly liquid.
In reply to DaveHK:
Try renaming your bank overdraft (if you have one) as 'personal quantitative easing' and see what difference that makes to your credit rating and all things related. That little experiment will probably answer your question.
Try renaming your bank overdraft (if you have one) as 'personal quantitative easing' and see what difference that makes to your credit rating and all things related. That little experiment will probably answer your question.
1
In reply to DaveHK:
If you look up the definition of rock, then yeah it seems completely legit. I suppose it would be a metamorphic rock since glacier ice is formed by the pressure of overlying snow/firn.
If you look up the definition of rock, then yeah it seems completely legit. I suppose it would be a metamorphic rock since glacier ice is formed by the pressure of overlying snow/firn.
In reply to DaveHK:
What is a mineral?
Wiki seems to think rocks and minerals are different things.
I would say that water is an organic compound. Or at least it's pretty important in organic chemistry.
https://en.m.wikipedia.org/wiki/Mineral
What is a mineral?
Wiki seems to think rocks and minerals are different things.
I would say that water is an organic compound. Or at least it's pretty important in organic chemistry.
https://en.m.wikipedia.org/wiki/Mineral
1
In reply to DancingOnRock:
I thought an organic compound had to contain carbon?
> I would say that water is an organic compound
I thought an organic compound had to contain carbon?
Post edited at 16:42
4
In reply to DancingOnRock:
It certainly works based on the wikipedia definition of rocks and minerals.
I was really more interested in whether it was a useful definition, whether it carried our understanding forward in some way.
> What is a mineral?
> Wiki seems to think rocks and minerals are different things.
It certainly works based on the wikipedia definition of rocks and minerals.
I was really more interested in whether it was a useful definition, whether it carried our understanding forward in some way.
Post edited at 16:45
In reply to DaveHK:
I suspect, coming from that US Geological Survey source, that it’s a narrow and specific geological definition that follows logically if slightly unexpectedly from the classification of naturally occurring ice as a mineral. I don’t know whether this is a terminology that the British Geological Survey would follow. And yes, http://www.usgs.gov/faq/categories/9750/3470 further suggests that glacier ice should be categorised as a metamorphic rock; again, it’s just not the kind of metamorphosis that I’d usually think of. Of course some other geologically defined ‘rocks’, like clay for example, are (usually) considerably softer than glacier ice.
But personally I can’t see that defining ice as rock does anything to improve my understanding of its nature or properties!
I suspect, coming from that US Geological Survey source, that it’s a narrow and specific geological definition that follows logically if slightly unexpectedly from the classification of naturally occurring ice as a mineral. I don’t know whether this is a terminology that the British Geological Survey would follow. And yes, http://www.usgs.gov/faq/categories/9750/3470 further suggests that glacier ice should be categorised as a metamorphic rock; again, it’s just not the kind of metamorphosis that I’d usually think of. Of course some other geologically defined ‘rocks’, like clay for example, are (usually) considerably softer than glacier ice.
But personally I can’t see that defining ice as rock does anything to improve my understanding of its nature or properties!
In reply to Bob Aitken:
It might do more to change ones understanding of what rocks and minerals are rather than what glacial ice is.
>
> But personally I can’t see that defining ice as rock does anything to improve my understanding of its nature or properties!
> But personally I can’t see that defining ice as rock does anything to improve my understanding of its nature or properties!
It might do more to change ones understanding of what rocks and minerals are rather than what glacial ice is.
In reply to DaveHK:
Can some rocks flow by deformation of their crystals? Or all rocks under certain conditions?
Can some rocks flow by deformation of their crystals? Or all rocks under certain conditions?
Post edited at 17:02
In reply to DancingOnRock:
That's because they are. Minerals can be represented chemically and form identifiable crystals. For example: quartz (SiO2) is a mineral. All bits of quartz can be reduced down to SiO2 in a basic, specific structure (i.e. tetrahedra).
Rocks are comprised of minerals, and do not exhibit enough chemical consistency to be classified as one thing. For example: granite is made of a combination of quartz, feldspar(s) and other acessory minerals, such as amphibole and biotite. However, a granite can contain varying proportions of each, and still remains a granite - hence why some appear to be pinker than others. It can't be reduced down to a specific unit.
Back to the topic - considering a glacier as a metamorphic rock is very useful for studies of structural glaciology, where some processes (e.g. brittle deformation) are similar. Considering its a solid near to its melting point, as a rock in the lower crust/upper mantle is, this is a useful analogy for enhancing understanding of both glacial dynamics using existing geological knowledge, and geology as glacial ice moves, fractures and is modified on a time-scale orders of magnitude below that of rocks. However, structural glaciology is painfully "out of fashion" at the minute, and sees very limited study.
As to whether a glacier can/should be defined as a rock? Preferably not, otherwise I'll have to re-brand myself as a geologist.
> What is a mineral?
> Wiki seems to think rocks and minerals are different things.
That's because they are. Minerals can be represented chemically and form identifiable crystals. For example: quartz (SiO2) is a mineral. All bits of quartz can be reduced down to SiO2 in a basic, specific structure (i.e. tetrahedra).
Rocks are comprised of minerals, and do not exhibit enough chemical consistency to be classified as one thing. For example: granite is made of a combination of quartz, feldspar(s) and other acessory minerals, such as amphibole and biotite. However, a granite can contain varying proportions of each, and still remains a granite - hence why some appear to be pinker than others. It can't be reduced down to a specific unit.
Back to the topic - considering a glacier as a metamorphic rock is very useful for studies of structural glaciology, where some processes (e.g. brittle deformation) are similar. Considering its a solid near to its melting point, as a rock in the lower crust/upper mantle is, this is a useful analogy for enhancing understanding of both glacial dynamics using existing geological knowledge, and geology as glacial ice moves, fractures and is modified on a time-scale orders of magnitude below that of rocks. However, structural glaciology is painfully "out of fashion" at the minute, and sees very limited study.
As to whether a glacier can/should be defined as a rock? Preferably not, otherwise I'll have to re-brand myself as a geologist.
Post edited at 17:10
4
In reply to DaveHK:
I replied in a hurry earlier; I'll try again!
Firstly, I'll suggest that you'd have to jump through quite a few hoops to create a definition of 'mineral' that excluded ice, the naturally occurring crystalline form of hydrogen oxide. Like many other minerals, it has a variety of different solid phases it can form at different temperatures and pressures, and it can also be melted (or sublimed) by raising the temperature and/or decreasing the pressure.
Ice is naturally precipitated from the air or from water under certain conditions (compare clay minerals precipitating from river water when it changes chemical environment as it meets the sea, salts precipitating to form gypsum or halite as seawater evaporates, or silicate minerals precipitating in a magma chamber as it cools).
Snow or hail are sedimentary deposits, which can be reworked by the action of wind or avalanches, and consolidated into rock through compression, partial melting and refreezing, or freezing after the injection of more liquid (e.g. rain). After enough of this, you'd call it metamorphic rock, rather than sedimentary; there's a grey area between these anyway.
The crystals can grow and merge; the rock can move via creep, and can be folded, compressed, and remelted.
It can have inclusions of other rocks and minerals where they've been deposited along with it or picked up later; it can fail along fault lines and landslips when brittle, just like other rocks.
All in all, it's much like many other rocks, it just melts at a lower temperature than the ones we're used to.
Here are ice boulders on Enceladus:
http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=1622
Even better, ice boulders on Titan carried and rounded by methane rivers:
http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2348.pdf
I replied in a hurry earlier; I'll try again!
Firstly, I'll suggest that you'd have to jump through quite a few hoops to create a definition of 'mineral' that excluded ice, the naturally occurring crystalline form of hydrogen oxide. Like many other minerals, it has a variety of different solid phases it can form at different temperatures and pressures, and it can also be melted (or sublimed) by raising the temperature and/or decreasing the pressure.
Ice is naturally precipitated from the air or from water under certain conditions (compare clay minerals precipitating from river water when it changes chemical environment as it meets the sea, salts precipitating to form gypsum or halite as seawater evaporates, or silicate minerals precipitating in a magma chamber as it cools).
Snow or hail are sedimentary deposits, which can be reworked by the action of wind or avalanches, and consolidated into rock through compression, partial melting and refreezing, or freezing after the injection of more liquid (e.g. rain). After enough of this, you'd call it metamorphic rock, rather than sedimentary; there's a grey area between these anyway.
The crystals can grow and merge; the rock can move via creep, and can be folded, compressed, and remelted.
It can have inclusions of other rocks and minerals where they've been deposited along with it or picked up later; it can fail along fault lines and landslips when brittle, just like other rocks.
All in all, it's much like many other rocks, it just melts at a lower temperature than the ones we're used to.
Here are ice boulders on Enceladus:
http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=1622
Even better, ice boulders on Titan carried and rounded by methane rivers:
http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2348.pdf
In reply to DaveHK:
Yes, and by atoms from crystals migrating to their neighbours. It's a common process in the mantle - allowing solid, highly pressurised, rock to flow (slowly!)
> Can some rocks flow by deformation of their crystals? Or all rocks under certain conditions?
Yes, and by atoms from crystals migrating to their neighbours. It's a common process in the mantle - allowing solid, highly pressurised, rock to flow (slowly!)
In reply to skog (and Dave Kerr):
And so glacial meltwater must be a kind of lava, and when a glacial lake freezes it becomes a lava field.
I feel enriched by this idea - thanks.
And so glacial meltwater must be a kind of lava, and when a glacial lake freezes it becomes a lava field.
I feel enriched by this idea - thanks.
In reply to DaveHK:
all rocks under the right temp and pressure state
> Can some rocks flow by deformation of their crystals? Or all rocks under certain conditions?
all rocks under the right temp and pressure state
In reply to Wicamoi:
Yup! Albeit a monomineralic lava.
> And so glacial meltwater must be a kind of lava, and when a glacial lake freezes it becomes a lava field.
Yup! Albeit a monomineralic lava.
In reply to Webster:
It occurred to me after I posted that this might be a process by which rocks in the mantle flowed but it's not something I've thought about much.
I think that on the whole I shan't confuse my geography class with the notion that glacier ice is a monomineralic rock.
> all rocks under the right temp and pressure state
It occurred to me after I posted that this might be a process by which rocks in the mantle flowed but it's not something I've thought about much.
I think that on the whole I shan't confuse my geography class with the notion that glacier ice is a monomineralic rock.
In reply to ianstevens:
That's what I was thinking. You can't have monomineralic rock. It's a contradiction of terms.
A rock is composed of many minerals. Otherwise it would be a single mineral and, um, therefore a mineral.
I'd be interested to know exactly what lava is. Glacial meltwater is minerals (and rocks) in suspension of water. Probably some of which are dissolved to form dilute acids and alcalies.
That's what I was thinking. You can't have monomineralic rock. It's a contradiction of terms.
A rock is composed of many minerals. Otherwise it would be a single mineral and, um, therefore a mineral.
I'd be interested to know exactly what lava is. Glacial meltwater is minerals (and rocks) in suspension of water. Probably some of which are dissolved to form dilute acids and alcalies.
Post edited at 19:10
In reply to DancingOnRock:
I suppose that depends on how you define rock. Wikipedia (I know, I know) says: In geology, rock is a naturally occurring solid aggregate of one or more minerals or mineraloids.
> That's what I was thinking. You can't have monomineralic rock. It's a contradiction of terms.
> A rock is composed of many minerals. Otherwise it would be a single mineral and, um, therefore a mineral.
I suppose that depends on how you define rock. Wikipedia (I know, I know) says: In geology, rock is a naturally occurring solid aggregate of one or more minerals or mineraloids.
In reply to DancingOnRock:
Indeed. This dosen't exclude glaciers though - they're full of other bits of rock, dust and microbes.
No idea on the lava front beyond "liquid rock at the surface". By this definition it would include glacial melt if we're defining glaciers as rocks - however my understanding of geology terms is somewhat lacking.
> That's what I was thinking. You can't have monomineralic rock. It's a contradiction of terms.
> A rock is composed of many minerals. Otherwise it would be a single mineral and, um, therefore a mineral.
Indeed. This dosen't exclude glaciers though - they're full of other bits of rock, dust and microbes.
> I'd be interested to know exactly what lava is. Glacial meltwater is minerals (and rocks) in suspension of water. Probably some of which are dissolved to form dilute acids and alcalies.
No idea on the lava front beyond "liquid rock at the surface". By this definition it would include glacial melt if we're defining glaciers as rocks - however my understanding of geology terms is somewhat lacking.
In reply to DaveHK:
I was just thinking innit, gin on the rocks means gin with ice therefore ice is a rock?
I was just thinking innit, gin on the rocks means gin with ice therefore ice is a rock?
2
In reply to DancingOnRock:
In the real world, there are almost always impurities, but there are many rocks which can essentially be made of just one mineral, e.g. Quartzite, some types of anorthosite, some types of limestone (mostly made of calcite - though most have some other minerals too, such as siderite and dolomite).
There are different definitions of the word 'rock', but to be called that rather than just 'mineral' they'd generally be made of crystals or other pieces of the mineral which have grown together, or been brought together.
> A rock is composed of many minerals. Otherwise it would be a single mineral and, um, therefore a mineral.
In the real world, there are almost always impurities, but there are many rocks which can essentially be made of just one mineral, e.g. Quartzite, some types of anorthosite, some types of limestone (mostly made of calcite - though most have some other minerals too, such as siderite and dolomite).
There are different definitions of the word 'rock', but to be called that rather than just 'mineral' they'd generally be made of crystals or other pieces of the mineral which have grown together, or been brought together.
In reply to DaveHK:
This strikes me as a rather odd thread - ice isn't rock - it's frozen water innit!
Chris
This strikes me as a rather odd thread - ice isn't rock - it's frozen water innit!
Chris
1
In reply to DaveHK: I have to agree with Skog here. There are many rocks that are essentially monomineralic.
I was talking to some fellows last year who were mapping the base of the glacier via near surface seismic. Their methods for modeling the base of the glacier (ice on rock, ice on water, ice on shallow water) used standard equations and just treated the ice as a.n.other rock
I was talking to some fellows last year who were mapping the base of the glacier via near surface seismic. Their methods for modeling the base of the glacier (ice on rock, ice on water, ice on shallow water) used standard equations and just treated the ice as a.n.other rock
In reply to wbo:
This is it, really. It's just semantics - words mean what we want them to - but glacier ice is formed in a similar way to many other rocks, and behaves in much the same way. You have to make an effort to exclude it from being defined as a rock, unless to do with melting point. And we just do that because of what we're used to; plenty of other environments exist, even on Earth.
The argument wouldn't even come up if we lived somewhere ice rarely melted, such as Titan!
> I was talking to some fellows last year who were mapping the base of the glacier via near surface seismic. Their methods for modeling the base of the glacier (ice on rock, ice on water, ice on shallow water) used standard equations and just treated the ice as a.n.other rock
This is it, really. It's just semantics - words mean what we want them to - but glacier ice is formed in a similar way to many other rocks, and behaves in much the same way. You have to make an effort to exclude it from being defined as a rock, unless to do with melting point. And we just do that because of what we're used to; plenty of other environments exist, even on Earth.
The argument wouldn't even come up if we lived somewhere ice rarely melted, such as Titan!
In reply to DaveHK:
ALSO, what about the Rock and Ice Club?? If ice is rock would the club's name be oxymoronic or whatever the heck the word is? Eh?
I dunno. Just trying to help.
ALSO, what about the Rock and Ice Club?? If ice is rock would the club's name be oxymoronic or whatever the heck the word is? Eh?
I dunno. Just trying to help.
1
In reply to DancingOnRock:
quartzite, chalk...
a 'rock' and a 'mineral' arent mutually exclusive terms. 'mineral' is a descriptor of a chemical state, ie SiO2 (silica/quartz), and 'rock' is a descriptor of a physical state - solid at earth surface T and P. it is also made up of (mostly) inorganic minerals (note plural), but those minerals can all have the same chemical composition, ie all be SiO2 - quartz - giving a quartzite.
i suppose the crux point is a rock has many crystals/grains, whereas a mineral is a descriptor of a singular crystal/grain (of which there may be many). so a single fist sized gemstone of quartz is not a rock, just a mineral as it is only 1 crystal. a fist sized agregate of quartz crystals would be a rock composed of a single mineral.
so yes glacial ice is very much a rock
> That's what I was thinking. You can't have monomineralic rock. It's a contradiction of terms.
quartzite, chalk...
> A rock is composed of many minerals. Otherwise it would be a single mineral and, um, therefore a mineral.
a 'rock' and a 'mineral' arent mutually exclusive terms. 'mineral' is a descriptor of a chemical state, ie SiO2 (silica/quartz), and 'rock' is a descriptor of a physical state - solid at earth surface T and P. it is also made up of (mostly) inorganic minerals (note plural), but those minerals can all have the same chemical composition, ie all be SiO2 - quartz - giving a quartzite.
i suppose the crux point is a rock has many crystals/grains, whereas a mineral is a descriptor of a singular crystal/grain (of which there may be many). so a single fist sized gemstone of quartz is not a rock, just a mineral as it is only 1 crystal. a fist sized agregate of quartz crystals would be a rock composed of a single mineral.
so yes glacial ice is very much a rock
In reply to Webster:
Thanks.
It's more about how it is constructed then.
A lake of water that freezes into ice is a single mineral.
A glacier, made up from lots of 'grains' of ice that have fallen as snow or hail or resulted from freeze/thaw processes and then compressed becomes a rock.
Thanks.
It's more about how it is constructed then.
A lake of water that freezes into ice is a single mineral.
A glacier, made up from lots of 'grains' of ice that have fallen as snow or hail or resulted from freeze/thaw processes and then compressed becomes a rock.
Post edited at 22:01
In reply to DancingOnRock:
No, not really. The wikipedia definition of a mineral is pretty good, and differentiates it from the definition of a rock.
In the example you describe the glacirt ice well. The frozen lake is not a mineral though, it is a large crystalline mass of a single mineral, ice. It can still act as a rock though in the right circumstances.
In your definition you would struggle i think with marble. We start with a limestone, a rock that we will (simplistically) describe as a rock deposited as a biogenic grains of the mineral calcium carbonate. It then gets metamorphosed to marble, involving bulk recrystallisation to a single crystalline mass. This is still a rock, not a mineral. The mineral is still calcite.
No, not really. The wikipedia definition of a mineral is pretty good, and differentiates it from the definition of a rock.
In the example you describe the glacirt ice well. The frozen lake is not a mineral though, it is a large crystalline mass of a single mineral, ice. It can still act as a rock though in the right circumstances.
In your definition you would struggle i think with marble. We start with a limestone, a rock that we will (simplistically) describe as a rock deposited as a biogenic grains of the mineral calcium carbonate. It then gets metamorphosed to marble, involving bulk recrystallisation to a single crystalline mass. This is still a rock, not a mineral. The mineral is still calcite.
In reply to DancingOnRock:
a frozen lake will still be multiple ice crystals so by my definition still a rock!
> Thanks.
> It's more about how it is constructed then.
> A lake of water that freezes into ice is a single mineral.
a frozen lake will still be multiple ice crystals so by my definition still a rock!
In reply to DaveHK:
water ice = igneous rock
nevee = sedimentary rock
glacier = metamorphic rock
water = magma
discuss
Don't you think your students would find that instructive?
water ice = igneous rock
nevee = sedimentary rock
glacier = metamorphic rock
water = magma
discuss
Don't you think your students would find that instructive?
In reply to DancingOnRock:
It depends on the context - what's more useful to call it at the time.
They aren't mutually exclusive terms, and there is not just one, fixed, definition of 'rock'. To further muddy it, not all rocks have to have crystals in them either - for example, obsidian (volcanic glass) doesn't. (Well, OK, the odd small one sometimes).
It depends on the context - what's more useful to call it at the time.
They aren't mutually exclusive terms, and there is not just one, fixed, definition of 'rock'. To further muddy it, not all rocks have to have crystals in them either - for example, obsidian (volcanic glass) doesn't. (Well, OK, the odd small one sometimes).
In reply to Wicamoi:
With some migmatite sections, maybe some sediment layers on top, and sometimes magma at the base!
Or lava.
> glacier = metamorphic rock
With some migmatite sections, maybe some sediment layers on top, and sometimes magma at the base!
> water = magma
Or lava.
In reply to skog:
Exactly - good discussion point. Loads for the inquiring mind to unravel and re-ravel
Exactly - good discussion point. Loads for the inquiring mind to unravel and re-ravel
1
In reply to DancingOnRock:
a crystal never becomes a rock, a crystal is a constituent part of a (but not all) rock/s.
> It what point does a crystal become a rock then.
a crystal never becomes a rock, a crystal is a constituent part of a (but not all) rock/s.
In reply to Wicamoi:
>
Teaching is a bit of a balancing act in this regard. The goal of all the pupils in that class is a good exam pass and it's my job to help them get that. I try to introduce lots of stuff over and above that to broaden out their learning and improve their understanding but it needs to be done carefully so that it doesn't confuse them especially as there are a wide range of abilities. I've found this discussion very interesting but I think it would confuse a lot of the pupils in the class and have little practical benefit for those that did understand. So for that reason I'll be leaving it out.
>
> Don't you think your students would find that instructive?
Teaching is a bit of a balancing act in this regard. The goal of all the pupils in that class is a good exam pass and it's my job to help them get that. I try to introduce lots of stuff over and above that to broaden out their learning and improve their understanding but it needs to be done carefully so that it doesn't confuse them especially as there are a wide range of abilities. I've found this discussion very interesting but I think it would confuse a lot of the pupils in the class and have little practical benefit for those that did understand. So for that reason I'll be leaving it out.
Post edited at 15:34
In reply to Doug:
A drift geological map will show 'recent' surface deposits such as peat.
It isn't rock in the same way mud isn't rock, but it can be consolidated to become rock (coal), just as mud can become mudstone.
A drift geological map will show 'recent' surface deposits such as peat.
It isn't rock in the same way mud isn't rock, but it can be consolidated to become rock (coal), just as mud can become mudstone.
This topic has been archived, and won't accept reply postings.
Loading Notifications...