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.

Planet Killers tend to have that affect

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.

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.

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.


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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

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
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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?

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.

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...

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).

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

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!

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...

The sun is the main source of heat. without it the earth would get very very cold. Colder then if the middle Mercury one side of the earth would have some heat (I am not sure how much) while the other side lost its heat and got cold very cold. The fourth state of matter is plasma and it has nothing to do with being a solid. Its sort of like liquid energy gas (Its kind of hard to explain). I think lightning is the only natural source of plasma on earth. And stop and think how thick 30 miles really is.

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).

I know lightning isn't plasma but it creates it. I didn't know fire was plasma though. You learn something everyday

actually I was thinking of contraction instead of expansion

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.

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.