does lava come from the centre of the earth?

Answer 1

Well, I wouldn't say the Earth's interior is theoretical (given, that term has a good deal of sway). We know about the Earth's interior thanks to seismic waves and their behavior as they run deeper. It is how we know about the liquid outer core, as well.

Given buoyancy models and what-not, as well as theoretical propagation experiments with certain compositions, we have a fairly good idea of the Earth's interior and make-up. All in all, it'd be pretty darn bizarre (and scientifically impossible) if we found out, for example, that the Earth is all liquid beneath the crust.

In response to steven's nice post, I have one thing to interject. The melts around Hawaii are particularly runny due to the composition of the lava. Popping through an oceanic plate boundary yields basaltic magma which is particularly runny (low viscosity) whereas the magma spewed from an inland, continental volcano is particularly viscous and not-quite-as-runny goop.

This is due to the two major sources from volcanism. One is from divergence zone (plates dividing. Only happens in oceanic plates) and convergence zones that undergo subduction (plates coming together. Can be ocean-ocean or cont'l-ocean flavors. Cont'l never subducts). Divergence rips an opening in the Earth's surface from plate divides and magma forms new plates, whereas subduction is a different entity. In subduction, a plate is crammed under another (lower density sinks beneath higher density. Think water-and-ice), and at a certain depth/temperature (also varies on angle of the plate's dip as well as composition), the plate will break down due to heat, and newly-formed magma will rise to the surface. This yields more viscous magma on continental regions because along the way, silicates are consumed by this flow. These contain volatiles (ie: H2O) that makes the magma less runny and more explosive (formation of oxygen and gases as a result of this. Makes for explosions!)

And to tag this misnomer, it is called magma when it's in the Earth. Once it has been shoved out much like a popped zit, it is known as lava.

Answer 2

There seems to be some confusion here with the answers above, so let me (a geologist) try to clear this up for you.

As simple as I can put it: Magma is the result of the partial melting of mantle rocks which occurs below the crustal rocks. There's a bunch of vocabulary here that I'll ignore to keep this clear. One: convecting mantle rocks are brought upwards and at a certain pressure & temperature will being to melt (like an ice cube)--mantle rocks are in a plastic state (not quite solid, not quite liquid). This is one source of magma and is called a "hot spot". Two: At subducting plate boundaries, the down-going plate also reaches pressures and temperatures where it is forced to give up it's water. As this happens, it triggers the surrounding rocks to being to partially melt...and bingo, a new magma source.

Mantle magmas are very "runny" ( low viscosity) and generate lavas like you see in Hawaii. Subduction generated magmas tend to be more viscous and produce lavas like those at mount St. Helens. Check your textbook and look at "Bowen's Reaction Series" - this will give the details you need fully get the picture.

Oh, and "no", magmas from the core do not reach the surface of the planet.

Hope this helps, and hope it isn't too simple for you.

(Marshall and Jim: Thanks for the nice words. Yes, I avoided going into discussing basalts, andesites, & granites, ion exchange, phase diagrams, etc. to try and keep the answer short and simple. My own college students sometimes get bogged down when a too detailed answer is given to a simple question. Still, I appreciate your additions. Cheers!)

Answer 3

No... magma (what lava is before it comes out) comes from deep in the Earth's mantle. The mantle is the layer between the crust and the core. It is created when the friction of shifting plates within the Earth creates heat and melts rock and other materials into a "liquid". I found a cool site that explains it for you below:

Answer 4

A comment relating to Steve's knowledgeable answer.

Be aware that no one has ever explored the mantle or the core. Scientific theory concerning this matter has apparently remained unchanged since I was a child, but realize that nearly everything we "know" about the interior of the earth (other than the crust) is theoretical. Someday, exploration of the depths of our planet will almost certainly surprise us all and change the current theory. A surprisingly well-worded and well-thought-out article here: http://en.wikipedia.org/wiki/Structure_of_the_Earth

Jim, http://www.jimpettis.com/wheel/

Answer 5

Lava is the molten flowing rocks spewed out of volcanoes.
Volcanos erruption are the results of earth electric currents flowing underground and melting stones and rocks.The pressure built up over time causes the volcano erruption.

Answer 6

No, it only comes from as far of the layer of the Earth known as the mantle

Answer 7

No. It comes from the magma layer just below the crust. The core is theoretical only. Humans don't have the capacity yet to reach it.

Answer 8

no it's comes from beneath the earth's mantel

Answer 9

yes