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 #22 Monday, December 29, 2003 5:03 PM
Reply #22 Monday, December 29, 2003 5:03 PM
We certainly have quite a bit left to learn, but that does not necessarily invalidate what we already do know.
There are quite a few things in the geological record that indicate that the gravitational force of earth was not significantly different from now. There apparently has been some variation, but that variation is currently estimated to be within a few percentage points at most.
Just as (to stay on topic) the evidence in favor of the accuracy of the plate tectonics model has a high level of confidence, and there is no clear evidence that the size of the earth has varied in any significant sense in the geological record.
As a scientist, I'm always open to new evidence and theories, but they'll generally have to subsume the observed and experimentally vetted body of evidence (in much the same manner that Einstein's laws of motion subsumed Newton's laws of motion).
There are quite a few things in the geological record that indicate that the gravitational force of earth was not significantly different from now. There apparently has been some variation, but that variation is currently estimated to be within a few percentage points at most.
Just as (to stay on topic) the evidence in favor of the accuracy of the plate tectonics model has a high level of confidence, and there is no clear evidence that the size of the earth has varied in any significant sense in the geological record.
As a scientist, I'm always open to new evidence and theories, but they'll generally have to subsume the observed and experimentally vetted body of evidence (in much the same manner that Einstein's laws of motion subsumed Newton's laws of motion).
Aleatoric
Reply #23 Monday, December 29, 2003 5:07 PM
You're welcome
That's one of the reasons I'm a scientist (well, actually I'm an engineer with an intense interest in science (and a minor in physics
)). It is *the* tool that we have to understand the world (and the universe) around us.
Reply #23 Monday, December 29, 2003 5:07 PM
| Thanks for that info on the core and the magnetic field. We are never too old to learn new things. I really was taught that the core was solid, this just shows what a dynamic field science is. |
You're welcome
That's one of the reasons I'm a scientist (well, actually I'm an engineer with an intense interest in science (and a minor in physics
)). It is *the* tool that we have to understand the world (and the universe) around us.
kongit
Reply #24 Monday, December 29, 2003 5:09 PM
Reply #24 Monday, December 29, 2003 5:09 PM
nobody actually knows what the core is. The one assumption I am familiar with is a large molten core of iron. I can't possibly see how the earth would expand. I could understand it contracting. The gravity of the earth is more likely to pull the particles of earth closer together then for any of the accountable reasons for it to expand. I can only think of two possible reasons for the earth to exand: the first is the inner core getting hotter (the whole earth for that matter) via global warming or some other oddity of nature, the other way is if gravity lost some of its hold and the spin of the earth pulled it apart (but that would result in the destruction of the earth and the lessening of gravity is improbable).
Aleatoric
Reply #25 Monday, December 29, 2003 5:20 PM
Reply #25 Monday, December 29, 2003 5:20 PM
Actually, based on seismic data, we have a reasonable good idea about the structure of the core. There are still unanswered questions (and possibly even a complete re-evaluation of the data might happen at some point), but there's a pretty high confidence factor in the current viewpoint.
The estimated temperature of the core is about 5000 to 7000 degrees Celsius (roughly equivalent to the temperature of the surface of the sun). It is cooling slowly (the current accepted idea is that it has cooled a few hundred degrees in the last 3 billion years). Radioactive decay replaces almost all heat that is lost.
Even the worst estimates about the impact of global warming would have no effect on the core temperature (or even the mantle temperature).
Expansion of the earth is considered at present to be highly unlikely (short of an infusion of a substantial amount of mass, which would have severely negative results for anything currently existing on the surface).
The estimated temperature of the core is about 5000 to 7000 degrees Celsius (roughly equivalent to the temperature of the surface of the sun). It is cooling slowly (the current accepted idea is that it has cooled a few hundred degrees in the last 3 billion years). Radioactive decay replaces almost all heat that is lost.
Even the worst estimates about the impact of global warming would have no effect on the core temperature (or even the mantle temperature).
Expansion of the earth is considered at present to be highly unlikely (short of an infusion of a substantial amount of mass, which would have severely negative results for anything currently existing on the surface).
kongit
Reply #26 Monday, December 29, 2003 5:31 PM
Reply #26 Monday, December 29, 2003 5:31 PM
If its cooling then the earth will slowly be contracting, no? I know that the estimates of temperature and size are pretty exact, but the materials that make it up are what I don't know.
Essencay
Reply #28 Monday, December 29, 2003 5:41 PM
Reply #28 Monday, December 29, 2003 5:41 PM
I am not a scientist, engineer, biologist, etc. I have read this thread with interest. In my ignorance, I ask about the shifting of continental land masses. Would that cause the areas they shift away from to thin, and over time cause the cooling of the earth's core to accelerate? Does the cooling of the earth's core put heat into the atmosphere? I apologize if this is not exactly on topic.
Aleatoric
Reply #29 Monday, December 29, 2003 5:46 PM
Reply #29 Monday, December 29, 2003 5:46 PM
The general school of thought was that the core was pretty much entirely iron (being the most abundant element). Seismic data indicates that the density of the core is less than it would be if it were entirely made of iron, and the current viewpoint is that the iron in the core also contains some amount of less dense material, such as silicon, etc.
Cooling would cause the earth to contract, but considering the pressures, etc., the magnitude of the shrinkage would be quite small as a percentage of the diameter of the earth. Off the cuff, I would estimate that if the core cooled completely, the shrinkage wouldn't be much more than a few hundred to maybe a thousand feet.
Cooling would cause the earth to contract, but considering the pressures, etc., the magnitude of the shrinkage would be quite small as a percentage of the diameter of the earth. Off the cuff, I would estimate that if the core cooled completely, the shrinkage wouldn't be much more than a few hundred to maybe a thousand feet.
Aleatoric
Reply #30 Monday, December 29, 2003 5:58 PM
Reply #30 Monday, December 29, 2003 5:58 PM
essencay,
Some heat is transmitted away from the mantle, but most of the energy expended goes to moving the crust (convection currents in the mantle, for example), and so forth. The rest goes into the environment (atmosphere and ocean). It's also generally accepted that the heat of the core is largely responsible for the overall liveable temperatures we have. I've read (and this is from memory, so it could be wrong, I'll have to do some fact checking in a bit) that if the core were cold, the surface tamperature of the earth would be well below freezing (maybe *much* below).
Given the relationship between surface area and volume, the amount of heat lost is related to surface area, and the amount of heat stored (and generated by the core) is related to volume, then the heat loss is very small, by percentage. Even if the entire surface was molten (and stayed that way) it would still take a substantial amount of time for the core to cool.
The crust tends to be thinner at the separation points, but as the spread continues, the crust thickens up due to sedimentation and solidified magma. It's also thinner at the subduction interfaces.
[Message Edited]
Some heat is transmitted away from the mantle, but most of the energy expended goes to moving the crust (convection currents in the mantle, for example), and so forth. The rest goes into the environment (atmosphere and ocean). It's also generally accepted that the heat of the core is largely responsible for the overall liveable temperatures we have. I've read (and this is from memory, so it could be wrong, I'll have to do some fact checking in a bit
) that if the core were cold, the surface tamperature of the earth would be well below freezing (maybe *much* below).Given the relationship between surface area and volume, the amount of heat lost is related to surface area, and the amount of heat stored (and generated by the core) is related to volume, then the heat loss is very small, by percentage. Even if the entire surface was molten (and stayed that way) it would still take a substantial amount of time for the core to cool.
The crust tends to be thinner at the separation points, but as the spread continues, the crust thickens up due to sedimentation and solidified magma. It's also thinner at the subduction interfaces.
[Message Edited]
e0n
Reply #31 Monday, December 29, 2003 8:52 PM
Reply #31 Monday, December 29, 2003 8:52 PM
u should check out the movie the core if stuff from there were to actually happen, especially the birds part, falling from the sky =X dope flick =X i would doubt the earth to be expanding id go with the earth cooling off =x
kongit
Reply #32 Monday, December 29, 2003 9:37 PM
Reply #32 Monday, December 29, 2003 9:37 PM
I got nothing to say after reading that. The spelling just shattered my mind. No offense e0n but use a spell checker or get a dictionary. We all mispell words now and then, but at least make an attempt at proper English.
I am starting to feel mean. Am I mean?
spelling
[Message Edited]
I am starting to feel mean. Am I mean?
spelling
[Message Edited]
Essencay
Reply #34 Tuesday, December 30, 2003 5:36 PM
If the shifting of plates causes separation points that are filled with sediment and magma and the other ends of the plates are pushing together to cause mountains, isn't that creating more surface area?
Reply #34 Tuesday, December 30, 2003 5:36 PM
| The crust tends to be thinner at the separation points, but as the spread continues, the crust thickens up due to sedimentation and solidified magma. It's also thinner at the subduction interfaces. |
If the shifting of plates causes separation points that are filled with sediment and magma and the other ends of the plates are pushing together to cause mountains, isn't that creating more surface area?
kongit
Reply #35 Tuesday, December 30, 2003 5:41 PM
Reply #35 Tuesday, December 30, 2003 5:41 PM
surface area has nothing to do with expansion. Theoretically you could have an object of a set mass and volume with an infinite amount of surface area. And I don't think that means that the surface area is increasing.
Fuzzy Logic
Reply #36 Tuesday, December 30, 2003 7:58 PM
Reply #36 Tuesday, December 30, 2003 7:58 PM
What is wrong with you people? Everyone knows the Earth is flat. Ha, if it wasn't I'd fall over a lot more than I do...
Aleatoric
Reply #37 Tuesday, December 30, 2003 8:23 PM
Reply #37 Tuesday, December 30, 2003 8:23 PM
Nah, even if it was flat, I'd still fall over
re surface area:
If you get a new mountain range, that could translate into a small increase in surface area, but as a percentage of the total surface area of the earth, the increase would be infinitesimal, for all intents and purposes. The simple surface area of the earth is 201,061,760 square miles (calculated as a sphere with radius of 4000 miles). Given the roughness of the surface features and a more or less fractal charactistic to that roughness, the effective surface area could be as much as (or more than) twice that. Given that the crust is a very effective insulator, though, the loss of heat due to radiation is relatively small.
Just for grins, the volume of the earth is 268,082,346,667 cubic miles (using the same values). Although not the correct values, if we say that the surface of the earth radiates heat at 1000 watts per square mile, the body of the earth would only have to generate 0.75 watts to about 1.5 watts of heat per cubic mile to keep up with the heat loss (again, rough calculations from a number pulled from the air, but the principle is correct).
re surface area:
If you get a new mountain range, that could translate into a small increase in surface area, but as a percentage of the total surface area of the earth, the increase would be infinitesimal, for all intents and purposes. The simple surface area of the earth is 201,061,760 square miles (calculated as a sphere with radius of 4000 miles). Given the roughness of the surface features and a more or less fractal charactistic to that roughness, the effective surface area could be as much as (or more than) twice that. Given that the crust is a very effective insulator, though, the loss of heat due to radiation is relatively small.
Just for grins, the volume of the earth is 268,082,346,667 cubic miles (using the same values). Although not the correct values, if we say that the surface of the earth radiates heat at 1000 watts per square mile, the body of the earth would only have to generate 0.75 watts to about 1.5 watts of heat per cubic mile to keep up with the heat loss (again, rough calculations from a number pulled from the air, but the principle is correct).
kona0197
Reply #38 Tuesday, December 30, 2003 8:45 PM
yep. and Al Gore created the internet
Reply #38 Tuesday, December 30, 2003 8:45 PM
| What is wrong with you people? Everyone knows the Earth is flat. Ha, if it wasn't I'd fall over a lot more than I do... |
yep. and Al Gore created the internet
joetheblow
Reply #39 Tuesday, December 30, 2003 10:40 PM
Really? And to think I thought the sun was the main source of heat.
Heat = energy???
Also if the Earth's core or for that matter most of its mass is still molten rock and minerals that is under so much pressure that it is almost solid, could it be considered the 4th state of mass? (I forget what it is called... plasma maybe?)
I have to say that being on a piece of crust that is, at most, 30 miles thick always seemed disturbing to me. I think we need mosre crust if you ask me. It should be at least 100 miles thick.
This wholes subject is just amazing to me. I love the whole idea of it!
Reply #39 Tuesday, December 30, 2003 10:40 PM
| but most of the energy expended goes to moving the crust (convection currents in the mantle, for example), and so forth. The rest goes into the environment (atmosphere and ocean). It's also generally accepted that the heat of the core is largely responsible for the overall liveable temperatures we have. I've read (and this is from memory, so it could be wrong, I'll have to do some fact checking in a bit ) that if the core were cold, the surface tamperature of the earth would be well below freezing (maybe *much* below). |
Really? And to think I thought the sun was the main source of heat.
Heat = energy???
Also if the Earth's core or for that matter most of its mass is still molten rock and minerals that is under so much pressure that it is almost solid, could it be considered the 4th state of mass? (I forget what it is called... plasma maybe?)
I have to say that being on a piece of crust that is, at most, 30 miles thick always seemed disturbing to me. I think we need mosre crust if you ask me. It should be at least 100 miles thick.
This wholes subject is just amazing to me. I love the whole idea of it!
IPlural
Reply #40 Tuesday, December 30, 2003 10:46 PM
Reply #40 Tuesday, December 30, 2003 10:46 PM
you mean, he didn't?
Well there is one thing I keep coming back to about the life cycle of the planet.
Weather patterns and pollutions do play the key part in global warming and at the same time so does tectonic plate subduction because it designs the Earth's contours which also play a key part in Weather patterns.
I would be curious to find something on the theory that the earth was in fact a ice encrusted planet which was 8 - 10 feet thick at it's thinest point. I wonder how much it would have impacted the dia. of the planet and would it actually be enough to affect the over all density.
anyway...
Well there is one thing I keep coming back to about the life cycle of the planet.
Weather patterns and pollutions do play the key part in global warming and at the same time so does tectonic plate subduction because it designs the Earth's contours which also play a key part in Weather patterns.
I would be curious to find something on the theory that the earth was in fact a ice encrusted planet which was 8 - 10 feet thick at it's thinest point. I wonder how much it would have impacted the dia. of the planet and would it actually be enough to affect the over all density.
anyway...
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Reply #21 Monday, December 29, 2003 4:58 PM