This maybe a stupid question but i was asleep during much of my schooling so now i tring to catch up. So if there’s anyone who’d care to help :
What keeps the earths core so hot ? and with all the eruptions where is all the lava coming from ? I mean you’d figure it would cool off after awhile…And why isn’t the core going empty…???
I think the most accepted answer is that the decay of radioactive isotopes in the core provides the heat to keep it hot. I don’t believe that is the whole story, though.
Although I know nothing about this at all (you slept, I just didn’t go), I would like to venture in with pressure. I would figure that the weight of the rest of the earth bearing down on the core would produce some pretty serious heat.
The last time I heard, no one’s really sure why the core is so hot. But there are some theories.
The Earth was formed molten, and there’s a heckuva lotta stuff here. Even without any further explanations, the core would still be hot. 4.5 billion years would not be enough time for it to cool completely. Remember, we’re surrounded by the vacuum of space. So the only way for the heat to escape is through radiation. Infrared isn’t that efficient a way to shed Kelvins.
However, it should be cooler than it is, given the temperature it supposedly had at formation and radiating for 4 million million years. So they still don’t know. The idea of heating by radioactive decay is one theory. Others include the idea that gravitational tides help stoke the furnace. Hopefully, a geophysicist is reading this and will give us the latest ideas.
Back to your OP, the core isn’t ‘going empty’ because the stuff it sprays about on the surface doesn’t all stay up here. I’m sure you’ve heard of Plate Tectonics. As the various parts of the crust move around, some parts are forced down under other parts. You end up with a mountain range on our side of the crust, but the part that goes down is melted into the mantle.
By the way, that’s another bit of terminology you should know. The lava seen in eruptions comes from the molten ‘mantle’ below the crust. The core is a lot further down, and is mostly made of iron and nickel. It’s partially molten but some of it is solid due to the pressure, if I recall correctly.
I am trying to remember my Stephen Hawking, and I think all of those answers play a part in it. I suspect also that heat is being added to the Earth by the sun, and perhaps the Earth’s core keeps much of the heat trapped inside, acting sorta like insulation.
The last time I heard, no one’s really sure why the core is so hot. But there are some theories.
The Earth was formed molten, and there’s a heckuva lotta stuff here. Even without any further explanations, the core would still be hot. 4.5 billion years would not be enough time for it to cool completely. Remember, we’re surrounded by the vacuum of space. So the only way for the heat to escape is through radiation. Infrared isn’t that efficient a way to shed Kelvins.
However, it should be cooler than it is, given the temperature it supposedly had at formation and radiating for 4 thousand million years. So they still don’t know. The idea of heating by radioactive decay is one theory. Others include the idea that gravitational tides help stoke the furnace. Hopefully, a geophysicist is reading this and will give us the latest ideas.
Back to your OP, the core isn’t ‘going empty’ because the stuff it sprays about on the surface doesn’t all stay up here. I’m sure you’ve heard of Plate Tectonics. As the various parts of the crust move around, some parts are forced down under other parts. You end up with a mountain range on our side of the crust, but the part that goes down is melted into the mantle.
By the way, that’s another bit of terminology you should know. The lava seen in eruptions comes from the molten ‘mantle’ below the crust. The core is a lot further down, and is mostly made of iron and nickel. It’s partially molten but some of it is solid due to the pressure, if I recall correctly.
[I bet this double-posted. Sorry about that. I noticed that I put in a mistake just as I submitted, then tried to stop and correct it. But I wouldn’t be surprised if the first one got through.]
Because that’s where Hell is located.
Didn’t you learn anything in Sunday School?
Re: Saltire’s double post
Oh, I thought one version was the British age of the earth and the other was the American age of the earth.
BTW, which is the real Earth’s core thread?
panama jack
I am also at this point accustomed to reaffirm with emphasis my conviction that the sun is real, and also that it is hot–in fact hot as Hell, and that if the metaphysicians doubt it they should go there and see.
– Winston Churchill
Our planet was molten and forming a little over 4 billion years ago. Four billion years later it has cooled off considerably and formed a crust (which is our foundation). We know quite a bit about the crust of the Earth, but we know far less about the several layers beneth it. Once you go say 25-30 miles down of where you are reading this (unless you’re in an airplane!). We run into the mantle which is about 2,800 miles in thickness. Enormous temperatures and pressures present here keep much of the mantle SOLID. The next layer, dubbed the “outer core” is about as thick as the mantle. This layer most likely consists of iron alloyed with some light metal. Then you have the core which is probably all iron.
Currently, there are many factors which “keep the heat” down there. Some have already been mentioned (and some are unknown).
-Mike
I think, as mentioned above, that tidal gravitational forces have a lot to do with keeping the core so hot. This is the reason Jupiter’s moon Io is practically molten.
The main reason is radioactive decay. Note, in the mid 19th century scientists tried to calculate the age of the Earth assuming it was once molten and slowly cooled. How long would it take? The figures they arrived at were about 50 million years or so. Problem, Darwin has just published Origin of Species and according to his theory 100s of millions of years are necessary for evolution to take place impossible if the Earth is only a few million years old. Lord Kelvin I believe could not take evolution seriously because his calculation showed that the Earth was too young. In the late 1890s radioactivity was discovered and the mystery was solved.
The mantle isn’t molten; it’s solid. The very top of the asthenospheric mantle is partially molten (just a couple of percent, though, and we call this part the “low velocity zone”), but the mantle is solid. Ductile, but solid nonetheless.
(Another bit of terminology: Lava is what it’s called only at the surface; otherwise, it’s magma.) Magmas aren’t necessarily generated in the mantle–they can also form by heating up the crust (by the intrusion of magma that was generated in the mantle, but it’s still formed in the crust).
Outer core = liquid; Inner core = solid. Both are dominated by iron and the siderophile elements that love it so.
This has to be the biggest variable, but there are so many…
This is one of those nobody knows questions. Without recapping what everyone else has said, let me add that the crust and mantle impede heat dissipation quite well. Lots of other influences affect surface temperature, particularly solar radiation, which is absorbed by sea water. One effect of the moon’s orbit that has been proposed is that it may modulate the influx of meteoric dust which may affect solar heating of the earth by absorption. These influences on surface temperature are small compared to the temperatures in the core (long time estimates of ~3000º C have risen of late up to as much as 6000º C), but they do serve to buffer the crusts’ effectiveness as a barrier to dissipation of heat energy.
So, the earth retains quite a bit of heat as yet, and structural effects of the ongoing chemical and thermal development of the earth’s interior felt on the surface continue apace, so far. Nobody can reproduce conditions similar to those anticipated in the deep interior, so we’re left with speculation; but generally it’s thought that while much of the heat generating radioactive decay has ceased, nobody can predict where we really are on a thermal decline curve for the planet.
As a planet contracts, its temperature increases. I’m not sure if the earth is contacting (if it is, it’s doing so very slowly). I have read about a hypothesis that the reason all the gas giants except Uranus radiate more energy than they receive from the sun is that they are still contracting.
I have leaned alot from all this flow of knowledge, but it brings more questions. 1) How do we really know what is at the earths core ? is there proof ? or is it just a guess ?
Still Learning…
Well a lot of the insights in this thread have come about through the study of earthquakes and the resultant shock waves. If an earthquake occurs various different sensing stations dotted around the earth pick up the vibrations coming through the ground. There are different types of shockwaves too (primary or P-waves and secondary of S-saves) depending on whether they shake the ground in an up-down way or in a side to side way and whether they travel over the surface of the earth of through the middle.
Just like waves on water they refract and reflect, create interference patterns etc etc and the detailed analysis of all that allows the scientists to deduce the different zones (and sub-zones) of the earth and their composition from things like the density of the material (waves travelling at different speeds depending on the density of the material through which they are travelling).
Radioactive decay is not the main reason that the Earth’s core is so hot. Most of the earth’s radioactive material is concentrated in the outermost layers. Kelvin’s calculations assumed that the heat loss at the surface was representative of the heat loss at the core–but most of the heat loss at the surface is due to those radioactive elements. That is what threw off his calculations.
Darwin accepted Kelvin’s calculations, because they were within the tolerances of his theories. Many years later, Kelvin revised his estimates to an even shorter time–just a few years before radioactivity was discovered.
…but it’s related and I hate to start another thread for it.
If the earth’s core were to completely cool off (say over the next year) would we notice anything different on the surface (for now forget inertial forces that might shove continents around if everything went ‘solid’ that quickly…that’s not what I’m interested in).
I suppose earthquakes and volcanos would stop but I’m more interested if the core contributes anywhere near a significant amount of heat to the atmosphere. Would it be enough to kick off an ice age? Or worse? Or would we merrily go on our way none the wiser?
Heat conduction from the core takes many years, but convection only takes a few million. On the other hand, the magnetic field of the earth depends a lot upon the liquid outer core, which is probably stirred by currents created by the cooling of the inner core. So, if the outer core completely solidified, the magnetic field would drop considerably.
But that’s like the hypothetical question of the moon disappearing–can’t happen in any reasonable scenario.