# Where does the energy for a tsunami come from initially? **URL:** \ **Category:** Factual Questions\ **Created:** [January 10, 2005, 6:01pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073 "2005-01-10T18:01:39Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![FlippyFly](https://avatars.discourse-cdn.com/v4/letter/f/e95f7d/32.png) [@FlippyFly](https://boards.straightdope.com/u/FlippyFly)\ **Post date:** [January 10, 2005, 6:01pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/1 "2005-01-10T18:01:39Z")
The tsunami released incredible amounts of energy – where did the energy come from initially? An earthquake triggered the waves, so the energy came from the earthquake. The earthquake’s energy comes from the tectonic plates movements… so what is powering the plates to move? Is it something to do with the molten core? Somehow related to the earth’s rotation? Something to do with the sun? ---
**Author:** ![RumMunkey](https://avatars.discourse-cdn.com/v4/letter/r/b19c9b/32.png) [@RumMunkey](https://boards.straightdope.com/u/RumMunkey)\ **Post date:** [January 10, 2005, 6:06pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/2 "2005-01-10T18:06:52Z")
[How earthquakes work.](http://science.howstuffworks.com/earthquake.htm) [How Tsnuamis work.](http://science.howstuffworks.com/tsunami.htm) ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [January 10, 2005, 6:09pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/3 "2005-01-10T18:09:54Z")
The plates sit on the molten core and drift very slowly. Sometimes they might become ‘snagged’ (although I’m not sure whether the recent earthquake was an incidence of this particular kind of earthquake) and potential energy builds up at the snag point rather like the energy stored in a compressed spring. When the snag suddenly ‘gives’, all of that energy is released immediately, in this case with tragic results. And yes, that energy _originally_ came from the rotational energy of the disc of material which ultimately formed the solar system. ---
**Author:** ![FlippyFly](https://avatars.discourse-cdn.com/v4/letter/f/e95f7d/32.png) [@FlippyFly](https://boards.straightdope.com/u/FlippyFly)\ **Post date:** [January 10, 2005, 6:16pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/4 "2005-01-10T18:16:04Z")
still not quite what i was looking for. Here, complete this chain: Tsunami \<— Earthquake \<---- Plate Movements \<----- ??? maybe it lookes like this: Tsunami \<— Earthquake \<---- Plate Movements \<----- Earth’s Rotation \<----- Gravitational Forces Or more like this: Tsunami \<— Earthquake \<---- Plate Movements \<----- Uneven heating of Earth \<---- Solar Energy \<---- Nuclear Fusion ---
**Author:** ![FlippyFly](https://avatars.discourse-cdn.com/v4/letter/f/e95f7d/32.png) [@FlippyFly](https://boards.straightdope.com/u/FlippyFly)\ **Post date:** [January 10, 2005, 6:17pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/5 "2005-01-10T18:17:28Z")
> [@SentientMeat](#): > > And yes, that energy _originally_ came from the rotational energy of the disc of material which ultimately formed the solar system. So it’s just momentum that keeps the plates moving now? ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [January 10, 2005, 6:27pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/6 "2005-01-10T18:27:45Z")
> [@](#): > > So it’s just momentum that keeps the plates moving now? Yes, at least it’s conservation of angular momentum (not, as we might be led to believe, love or money) which makes the world go round, and simple thermodynamics which melted that material under the huge pressures from gravity. ---
**Author:** ![FlippyFly](https://avatars.discourse-cdn.com/v4/letter/f/e95f7d/32.png) [@FlippyFly](https://boards.straightdope.com/u/FlippyFly)\ **Post date:** [January 10, 2005, 6:32pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/7 "2005-01-10T18:32:38Z")
> [@SentientMeat](#): > > Yes, at least it’s conservation of angular momentum (not, as we might be led to believe, love or money) which makes the world go round, and simple thermodynamics which melted that material under the huge pressures from gravity. So every time you have a major earthquake and all that energy is released, do the plates slow down a bit? If we wait long enough, will they stop moving all together, or is there energy going into the system as well as out? ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [January 10, 2005, 6:36pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/8 "2005-01-10T18:36:20Z")
> [@SentientMeat](#): > > …and simple thermodynamics which melted that material under the huge pressures from gravity. The real underlying root of the energy is radioactive decay more than anything else. > [@](#): > > The Earth emits more heat than it absorbs from the sun, and part of the reason for this excess heat is the decay of radioactive elements in the Earth. There are other sources of heat in the Earth, including thermal energy left over from when the Earth first formed, thermal energy from the large collision that formed the moon, and thermal energy remaining from the formation of the Earth’s core. However, these other sources of thermal energy are not as long-lasting as that from radioactive decay of natural elements in the Earth. > > SOURCE: [http://hps.org/publicinformation/ate/q2867.html](http://hps.org/publicinformation/ate/q2867.html) ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 10, 2005, 6:38pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/9 "2005-01-10T18:38:21Z")
> [@FlippyFly](#): > > So every time you have a major earthquake and all that energy is released, do the plates slow down a bit? If we wait long enough, will they stop moving all together, or is there energy going into the system as well as out? There is energy going into the system. Some of the heat that keeps the Earth’s mantle molten comes from the nuclear breakdown of radioactive elements, and some comes from tidal friction caused by the Moon. Both of these sources of energy will peter out eventually, since the Moon is slowing pulling away, causing progressively less tidal friction, and the radioactive elements will eventually break down into stable elements. When that happens, the Earth’s interior will continue to cool off slowly until it becomes geologically dead. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [January 10, 2005, 6:38pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/10 "2005-01-10T18:38:32Z")
Well there’s a fair bit of internal heating tied directly to radioactive decay within the Earth. Now tie that to convection currents within the outer core and mantle and you have a driver for the movement of the plates. They effectively float on a slowly roiling bed of molten rock. Once two (or more) plates move past each other you have the potential for a region to lock and so store energy. Once the region slips that energy gets released as kinetic movement which can tick off a tsunami. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [January 10, 2005, 6:40pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/11 "2005-01-10T18:40:46Z")
The collapse of the accretion disk that formed our solar system concentrated the kinetic energy of the moving matter that remains in the form of planets. That kinetic energy causes the rotation, and revolution of the various objects, and also the residual heat of formation. There is some difference of opinion whether all the interior heat of the Earth derives from that source, or if the decay of radioactive elements in the interior also contributes in some significant amount. Either way, the center is still very hot. The crust is not, and tectonic movement is the current mechanism whereby some fraction of that thermal energy gets turned back into kinetic energy. Tectonic movement is gradual, in gross terms, but very sudden, in the case of particular events. The case here is an extreme example. The plates beneath the sea gave way very suddenly, and allowed a very large movement along a rather long distance. Look at a nearby mountain range, and imagine it jumped up in the air, a few feet, and moved toward you a few yards. That’s a big expenditure of energy. Now, imagine the same thing under the ocean. That mountain will push a lot of water foreword, and that water will surge away, in a roughly circular wave motion. Then the water will slosh back, and then bounce off the bottom, and surge again. Now, the amount of water actually moved, and the distance it travels is not the whole story. The shock wave moves through the water, and in the deep ocean, it is not a huge wall of water, but rather a very strong, though shallow ripple. It also moves very fast, in the open ocean. When it runs into a shoreline, it gets compressed from the thousands of feet depth, into a much slower moving actual mass of water that gets propelled up the shore. The slope of the undersea shallows has a strong influence on what results, but in any case, the energy is expended by lifting water up beyond normal sea level, and the water then flows onto, and then comes back. ## Tris “Sic transit gloria mundi. And Tuesday’s usually worse.” ~ Robert A. Heinlein ~ ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [January 10, 2005, 6:43pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/12 "2005-01-10T18:43:39Z")
> [@](#): > > So every time you have a major earthquake and all that energy is released, do the plates slow down a bit? If we wait long enough, will they stop moving all together, or is there energy going into the system as well as out? IANA geophysicist (and what exactly happens in those billions of cubic metres below the surface is one of the most mysterious areas of science of all - we arguably know more about the insides of stars hundreds of light years away than the stuff between us and Australia), but the ‘snag’ of two plates is by definition a static phenomenon - they don’t ‘slow down’. Yes, there are other sources of enery as **Whack** quite rightly points out, but ultimately that leftover heat from Earth’s formation will radiate away, the radioactive isotopes will all be spent, the sun will die, and everything will slow to a cold, boring monotony. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 10, 2005, 6:48pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/13 "2005-01-10T18:48:10Z")
> [@SentientMeat](#): > > …ultimately that leftover heat from Earth’s formation will radiate away, the radioactive isotopes will all be spent, the sun will die, and everything will slow to a cold, boring monotony. And you think your heating bills are high _now_! ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [January 10, 2005, 6:50pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/14 "2005-01-10T18:50:03Z")
> [@Triskadecamus](#): > > There is some difference of opinion whether all the interior heat of the Earth derives from that source, or if the decay of radioactive elements in the interior also contributes in some significant amount. I was always under the impression that radioactive decay was the major source of core heating. Or rather, contibutes drastically to slowing the cooling of the planet (from the heat leftover by formation) to the point that without it the earth would have little in the way of a molten core left today without it. > [@](#): > > Radioactive heating of the Earth’s interior has always been crucial to the grand questions of our planet’s history. Shortly before radioactivity was discovered in the nineteenth century, the physicist Lord Kelvin estimated that it would have taken the Earth just 98 million years since its formation to cool to its present state. But by 1907, American radioactivity pioneer B. B. Boltwood realized that the extra heat provided by the decay of radioactive elements in the Earth means that the planet could be much older, perhaps even a few billion years. > > SOURCE: [http://www.ecology.com/ecology-news-links/2003/articles/5-2003/5-8-03/potassium.htm](http://www.ecology.com/ecology-news-links/2003/articles/5-2003/5-8-03/potassium.htm) ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [January 10, 2005, 6:54pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/15 "2005-01-10T18:54:02Z")
> [@Whack-a-Mole](#): > > I was always under the impression that radioactive decay was the major source of core heating. Or rather, contibutes drastically to slowing the cooling of the planet (from the heat leftover by formation) to the point that without it the earth would have little in the way of a molten core left today without it. I happen to agree with you, for all my lay opinion is worth. I just felt that I should point out that academic opinion is not unanimous on this point. (Surprise, surprise surprise, Sergeant Carter!) ## Tris “If we are going to stick to this damned quantum-jumping, then I regret that I ever had anything to do with quantum theory.” ~ Erwin Schrodinger ~ ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [January 10, 2005, 7:04pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/16 "2005-01-10T19:04:17Z")
It might be worth noting that for all the trouble the molten core gives us in the way of earthquakes and tsunamis without it we’d be much worse off. The core is what generates the earth’s magnetic field. Without that not only would Cub Scouts find their compasses useless we wouldn’t have much in the way of an atmosphere left (the field helps deflect the solar wind). ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 10, 2005, 7:09pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/17 "2005-01-10T19:09:11Z")
> [@Triskadecamus](#): > > The collapse of the accretion disk that formed our solar system concentrated the kinetic energy of the moving matter that remains in the form of planets. That kinetic energy causes the rotation, and revolution of the various objects, and also the residual heat of formation. There is some difference of opinion whether all the interior heat of the Earth derives from that source, or if the decay of radioactive elements in the interior also contributes in some significant amount. All the references I’ve ever seen indicate that radioactive decay is the major source of the Earth’s internal heat, with a lesser contribution from residual heat from the Earth’s formation, and some also coming from frictional heat due to the Moon’s gravitational attraction. I’ve never seen any reference that alleged that all of the heat was residual heat from formation. What’s your source on that? ---
**Author:** ![FlippyFly](https://avatars.discourse-cdn.com/v4/letter/f/e95f7d/32.png) [@FlippyFly](https://boards.straightdope.com/u/FlippyFly)\ **Post date:** [January 10, 2005, 7:20pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/18 "2005-01-10T19:20:10Z")
So let’s see if this is right: Tsunami \<- Earthquake \<- Plate Movements \<- Moltan Core \<- Radioactive Decay Where do we go next? What initially puts the energy in a chunk of Uranium? I would like to get this all the way back to the big bang, if possible, but I seem to recall that after the big bang, there was only hydrogen and helium in the universe, and all the rest of the elements were formed inside of stars? Is that correct? ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [January 10, 2005, 7:23pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/19 "2005-01-10T19:23:12Z")
> [@Colibri](#): > > I’ve never seen any reference that alleged that all of the heat was residual heat from formation. What’s your source on that? > [@SentientMeat](#): > > And yes, that energy originally came from the rotational energy of the disc of material which ultimately formed the solar system. :smack: 😛 ## Tris “What have you done to that cat? It looks half dead!” ~ Mrs. Erwin Schrodinger ~ ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [January 10, 2005, 7:31pm UTC](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073/20 "2005-01-10T19:31:29Z")
> [@FlippyFly](#): > > So let’s see if this is right: > > Tsunami \<- Earthquake \<- Plate Movements \<- Moltan Core \<- Radioactive Decay > > Where do we go next? What initially puts the energy in a chunk of Uranium? > > I would like to get this all the way back to the big bang, if possible, but I seem to recall that after the big bang, there was only hydrogen and helium in the universe, and all the rest of the elements were formed inside of stars? Is that correct? Ultimately the elements occur due to gravity (compressing the lighter elements), the strong force, weak force (radioactive decay) and electromagnetism. So the answer is that the energy arises from the way the universe is. [Next page](https://boards.straightdope.com/t/where-does-the-energy-for-a-tsunami-come-from-initially/284073.md?page=2)