Plate Techtonics: Is the Earth getting Bigger?
Monday, December 29, 2003 by joetheblow | Discussion: WinCustomize Talk
Where are all the science freaks around here???
http://www.sciencegroups.com/viewtopic.php?t=5445
I have always been amazed by plate techtonics and all this 'one plate going under or over' business.
Well in this thread on the linked site, one guy is saying that maybe the theory behind plate techtonics are wrong.
What do you think? And for that matter I thought plate techtonics was a law not a theory.
http://www.sciencegroups.com/viewtopic.php?t=5445
I have always been amazed by plate techtonics and all this 'one plate going under or over' business.
Well in this thread on the linked site, one guy is saying that maybe the theory behind plate techtonics are wrong.
What do you think? And for that matter I thought plate techtonics was a law not a theory.
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Aleatoric
Reply #42 Tuesday, December 30, 2003 11:39 PM
Reply #42 Tuesday, December 30, 2003 11:39 PM
jtb,
Yep, heat is energy
(actually, at some level, everything is energy [E=mc^2]).
The earth gets energy from the sun as well (and it's important), but without the warming effect of the core, the climate on the earth would probably be much like that on the moon, either really hot, in the sun, or really cold, in the dark.
IIRC, it's generally considered that the combination of inner earth temperature, nice orbital position (right amount of sun), and enough mass to retain a decent atmosphere is what makes earth as habitable as it is.
IPlural, what you're talking about is the 'snowball earth', a state that did exist quite some time ago (couple billion years, iirc). The increase in diameter from ice was negligable, but one of the things that allowed the ice to melt at all was volcanic action (without it, the ice reflected a lot of the energy of the sun back into space, with not enough left to melt the ice by itself).
Lightning isn't plasma, although it generally creates some in the air as it ionizes it. The plasma that most people are familiar with is a common flame.
The core of the earth is solid, not because it's a special state of matter, but because at the extremely high pressures at the core, the metal is pressure frozen, despite being at such a high temperature.
Also, the temperature of the inner earth drops as it gets closer to the crust, the outer core is cooler than the inner core, and the mantle is cooler than the outer core.
As for the crust, 30 miles is pretty much it (i think the range is from about 4 miles at the thinnest to about 37 miles at the thickest parts).
Yep, heat is energy
(actually, at some level, everything is energy [E=mc^2]).The earth gets energy from the sun as well (and it's important), but without the warming effect of the core, the climate on the earth would probably be much like that on the moon, either really hot, in the sun, or really cold, in the dark.
IIRC, it's generally considered that the combination of inner earth temperature, nice orbital position (right amount of sun), and enough mass to retain a decent atmosphere is what makes earth as habitable as it is.
IPlural, what you're talking about is the 'snowball earth', a state that did exist quite some time ago (couple billion years, iirc). The increase in diameter from ice was negligable, but one of the things that allowed the ice to melt at all was volcanic action (without it, the ice reflected a lot of the energy of the sun back into space, with not enough left to melt the ice by itself).
Lightning isn't plasma, although it generally creates some in the air as it ionizes it. The plasma that most people are familiar with is a common flame.
The core of the earth is solid, not because it's a special state of matter, but because at the extremely high pressures at the core, the metal is pressure frozen, despite being at such a high temperature.
Also, the temperature of the inner earth drops as it gets closer to the crust, the outer core is cooler than the inner core, and the mantle is cooler than the outer core.
As for the crust, 30 miles is pretty much it (i think the range is from about 4 miles at the thinnest to about 37 miles at the thickest parts).
kongit
Reply #43 Tuesday, December 30, 2003 11:43 PM
Reply #43 Tuesday, December 30, 2003 11:43 PM
I know lightning isn't plasma but it creates it. I didn't know fire was plasma though. You learn something everyday
IPlural
Reply #44 Wednesday, December 31, 2003 12:13 AM
Reply #44 Wednesday, December 31, 2003 12:13 AM
actually I was thinking of contraction instead of expansion 
Aleatoric
Reply #45 Wednesday, December 31, 2003 1:00 AM
Reply #45 Wednesday, December 31, 2003 1:00 AM
Ah, contraction
Can't really say for sure, the documentary I watched on the snowball earth didn't attempt to address that. I wouldn't think there would be much if any contraction, especially if the thickness of ice was essentially constant globally. Ice is less dense than the crust, and if it's pushing down equivalently all over, it would almost certainly have no substantial effect on either the diameter or average density of the earth.
That's not to say that ice can't have some effect, there's a valley in Greenland that has been 'pushed' down several hundred feet below sea level (at least) by the pressure of the ice above it. That kind of thing is usually made up for by an elevation of the crust somewhere else, though (which would leave the diameter and density essentially the same as before).
On an moderately related note, I'm currently watching a program that's speculating on what conditions on the earth would be like if we had no moon. While it is certainly all speculation, it discusses the idea that without the moon, apart from having much smaller tides (solar only), which could possibly have an effect on the origin of life, our atmosphere would likely be a mass of hurricane force winds. As I said, speculation, but it's an interesting idea to think about It's also fascinating, because it highlights the fact that a lot of the things we think we know in science (and other areas) often rest on similar speculations. We tend to support our speculations with evidence, and tailor them to fit the evidence, but there's no telling how far we are from grasping the whole of the picture. Kind of like trying to understand a human being by examining the relationship between their skin cells.
Can't really say for sure, the documentary I watched on the snowball earth didn't attempt to address that. I wouldn't think there would be much if any contraction, especially if the thickness of ice was essentially constant globally. Ice is less dense than the crust, and if it's pushing down equivalently all over, it would almost certainly have no substantial effect on either the diameter or average density of the earth.
That's not to say that ice can't have some effect, there's a valley in Greenland that has been 'pushed' down several hundred feet below sea level (at least) by the pressure of the ice above it. That kind of thing is usually made up for by an elevation of the crust somewhere else, though (which would leave the diameter and density essentially the same as before).
On an moderately related note, I'm currently watching a program that's speculating on what conditions on the earth would be like if we had no moon. While it is certainly all speculation, it discusses the idea that without the moon, apart from having much smaller tides (solar only), which could possibly have an effect on the origin of life, our atmosphere would likely be a mass of hurricane force winds. As I said, speculation, but it's an interesting idea to think about
It's also fascinating, because it highlights the fact that a lot of the things we think we know in science (and other areas) often rest on similar speculations. We tend to support our speculations with evidence, and tailor them to fit the evidence, but there's no telling how far we are from grasping the whole of the picture. Kind of like trying to understand a human being by examining the relationship between their skin cells.
joetheblow
Reply #46 Wednesday, December 31, 2003 7:51 PM
... say what????
So this state of matter that I thought was so hard to create because of the need for extreme heat... is right in my kitchen?
Well, at least its nice to know that the Earth is not going to explode in a rage of super hot rock due to the pressure the lava is under.
Reply #46 Wednesday, December 31, 2003 7:51 PM
| I didn't know fire was plasma though. You learn something everyday |
... say what????
So this state of matter that I thought was so hard to create because of the need for extreme heat... is right in my kitchen?
Well, at least its nice to know that the Earth is not going to explode in a rage of super hot rock due to the pressure the lava is under.
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Reply #41 Tuesday, December 30, 2003 10:46 PM