How does the composition of earth's crust lend evidence to the dynamo theory?
349081
Compare the cosmic abundance of iron and nickle to the abundance of those elements in the crust.
925593
Don't pay any attention to the girl who said, "So we won't float away." The earth's magnetic field has nothing to do with holding us to the earth. What seems to be happening, and this is still in the theory stage, is this. The solid inner core which is almost entirely iron and the liquid outer core which is probably composed mainly of a nickel-iron alloy are rotating at different speeds and because of the turbulence in the outer core they act together as a giant electric generator (dynamo) to produce an electric current. This in turn produces a magnetic field in the same way as an electric current passing through a coil forms an electromagnet. In other words the earth is a giant electromagnet which produces a field that can be measured far into space.
752486
These are all related to the crusts. \n\nA divergent boundary occurs when two Earth tectonic plates move away from each other, causing a depression or a range. \n\nSubduction occurs underwater when seawater tectonic plates converge into continental plates. Since seawater tectonic plates are more dense than continental plates, it 'subduct's and goes under. \n\nThere's more than 3 types of magma, depending on its temperature, density, and composition.\n\nAs you know, the plate tectonics theory says that the Earth's crust is moving constantly. By applying the observations of divergent boundaries through time (ex, Great Rift Valley created over centuries), that will -support- and -clarify- the plate tectonics theory. So, divergent boundaries being observed serves as evidence and support for the theory.\n\nSubduction occurs in sea-floor spreading, which explains why crusts closer to the mid-atlantic ridge are "warmer" and "younger", while the ones further away, and most likely closer to a subduction zone is colder. This shows that the Earth's crust is once again moving, once again indicating that the theory is true. \n\nMagma is formed when divergent boundaries move away from each other, and is replaced by new crusts formed by magma. The cycle of sea-floor spreading undergoing subduction, sinking under the continental crust, melting into magma, then re-forming  at the Mid-Atlantic ridge.
280671
the earth consist of 3 layers\n\n1) crust(lithosphere)\n2)mantle\n3)core (outer core n inner core)\n\na) core(innermost) is made up of FE-NI ALLOY\n     \n     inner core is solid and 650km depth\n\n     outer core is liqiuid & 2100 in depth\n\n\n b)mantle is about 2900 km thick\n\n\nc) crust thickness varies frm 10-50 km...it is made up  of  three types of rock
231903
In general, I agree with nacho track. There is more to it though. There is a huge mass of material in the core of the earth. A small portion of that is undergoing radioactive decay and creates heat which has to go to a colder place, as heat moves from places of greater heat to those of lesser heat as part of entropy,such as the surface of the earth. The magmas are heated by this decay and as they work their way to the surface of the earth, the pressure of rock and soil over them is lessened and the magma goes from a slightly plastic material to more or less a liquid.\n\nThe plates that underlie the crust of the earth are kept in motion because the heats does not escape evenly. There are places where continental plates are thicker and places where they are thinner.\n\nIf you ever made fudge candy, you will have observed pieces of crustier materials floating on a bed of liquid. They do move and create fissures and breaks and move slowly. Of course, if you are a good candy maker, you will stir the pot and spread the heat around so that the entire batch has reached the same degree of cooking. Earth is not stirred but just sits there like a big pot of fudge.
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Not at all. \n\nThe most convincing evidence that led to the acceptance of plate tectonic theory are stripes of magnetized rock that are arranged parallel the mid-ocean ridges and continue all the way to the edges of the ocean basins. These stripes grow progressively older in age as they approach the edges of the oceans, and correspond to past reversals of the earth's magnetic field. Each stripe formed during a period of Earth's history while the magnetic field orientation was steady, and as the field reversed, a new stripe with opposite orientation was formed. Here is a diagram that represents this:\nhttp://www.ucmp.berkeley.edu/geology/tecmech.html\n\nOther types of evidence that changed the paradigm from the old continental drift to plate tectonics was the discovery of mid-ocean ridges, which are volcanic chains larger than the Himalayas that stretch along the center parts of each ocean basin. These are active volcanic zones that are constantly forming new oceanic crust. \n\nPlate tectonics is an especially well proven and robust concept. Evidence of past plate movement is found in all parts of geology, from deposits of oil in both Africa and Brazil that came from the same source, to widespread rocks deposits on different continents that match in composition and character. Biological evidence in the form of fossils adds to the story, and plate tectonics is an important complement to the Theory of Evolution because it explains why some related organisms have had the opportunity to evolve differently in isolation. \n\nAs mentioned, the relatively new science of geodesy, prompted by satellite technology, can now measure the movement of continents precisely, and also can measure the changes in elevation of mountains as they rise. \n\nIf you would like to examine the changes in the earth's continental plates as a result of plate tectonics over time, here is a set of maps that show the movement of the earth's plates in the past and projected into the future:\nhttp://www.scotese.com/
1052897
Yes, there is a complex relationship.\n\nThe poles of the Earth's magnetic field actually change their locations across geological time.\n\nHowever, it's speculated that the Earth's magnetic field may be caused by a flow of liquid iron in the Earth's outer core, which might be affected in part, but not only, by Earth's rotation.
1119893
No it is not. Oceanic crust is composed primarily of basalt. Basalt is an extrusive igneous rock that cools quickly. Other types of rock commonly found on or beneath the unconsolidated sediments on the ocean floor are sedimentary rocks like sandstone, limestone, and shale. \n\nGranite is found in continental land masses. (Granite is NOT a metamorphic rock.) It is an intrusive igneous rock that must cool very slowly to form granite. \n\nHere is a good explanation with some illustrations:\nhttp://www.athro.com/earth_science/rocks.html
400182
I love this type of science - this is the only science that I know _-- Earth Science!\n\nIn 1963, Fred Vine, Drummond Matthews, and others found that the crust surrounding the midocean ridges showed alternating bands -- each band magnetized with a polarity opposite the surrounding bands. They suggested that as new sea-floor crust was formed around the rift in the midocean ridge, it magnetized differently, depending upon the polarity of the planet at that time. This supported the theory that Harry Hess had put forth, that the ocean progressivley widens as new sea floor is created along a crack that follows the crest of midocean ridges.\n\nIn 1966, earth scientists first identified the Jaramillo Event, the wholesale reversal of Earth's magnetic fields some 900,000 years ago. This confirmed the theory that Earth's magnetic field had flip-flopped through the planet's life, and it made Matthews and Vine's 1963 finding quite clear. They realized that the pattern of reversals matched perfectly the magnetic profile they had compiled of the sea floor. This discovery, together with data from a 1964 research vessel, transformed the field of geology. It confirmed sea-floor spreading as hypothesized by Hess, and thus "continental drift," originally proposed by Alfred Wegener back in 1912. It convinced many that plate tectonics was the best theory to unify nearly all the previously accumulated, but disjoint geological data.
51474
Actually, the very center of the earth is solid, composed mostly of iron and some nickel.  It's a solid because of the extreme pressures at the center of the earth (solids typically have denser crystal structures than their liquid forms).  It's very, very hot down there, but the effect of the pressure keeping the core solid outweighs the tendency of high temps to melt it.  Higher up, away from the inner core, the outer core is in fact molten, and this is due to the very high temperatures.  Here, the effect of the high temperatures outweighs the effect of the high pressures (not as high as in the inner core), and the material exists in its less dense, liquid form.
85089
Imagine that you had a big globe filled with Play-Dough and that this globe had cracks in it through which you suspected that Play-Dough was regularly squished from the inside of the globe onto the surface of the globe.  You know that all of the Play-Dough on the inside of the globe spontaneously changes from red to blue at somewhat regular intervals.  Now, you notice that on the outside of the globe, around the cracks, there are stripes of play-dough running parallel to the cracks in the globe...a red strip, and then a blue strip, and then a red strip, and then a blue strip...\n\nYou could reasonably surmise that the alternating red and blue stripes were created as Play-Dough from the inside of the globe was slowly, over a long period of time, squished out onto the surface of the globe, and the stripes originate as the Play-Dough on the inside of the globe suddenly changes from red to blue and back again.  As the Play-Dough is slowly squished out, it moves the Play-Dough that was squished out before it further from the crack, so the alternating stripes of Play-Dough (the plates of the earth) are slowly moving across the surface of the globe.\n\nThe red and blue Play-Dough represents the alternating magnetism of the earth...red is, say, when North points to what we now call North, and blue, the alternate color, is when the earth's magnetism flips and and North is South.  (During one of these periods a compass on earth would point South rather than North.)\n\nHope this helps
712469
The earth's crustal plates float on a layer called the Mantle, and it is convection in this mantle which drives the continental drift or plate tectonics.
840444
The origin of the Earth's magnetic field is not completely understood, but is thought to be associated with electrical currents produced by the coupling of convective effects and rotation in the spinning liquid metallic outer core of iron and nickel. This mechanism is generally known as the dynamo effect. \n\nBecause of the rotating outer core,it produces an electric current, which in turn, produces a magnetic field that also interacts with the fluid motion to create a secondary magnetic field. Together, the two fields are stronger than the original and lie essentially along the axis of the Earth's rotation.
1025704
Plate tectonics (from the Greek word for "one who constructs and destroys", τεκτων, tektōn) is a theory of geology developed to explain the phenomenon of continental drift and is currently the theory accepted by the vast majority of scientists working in this area. In the theory of plate tectonics the outermost part of the Earth's interior is made up of two layers: the lithosphere comprising the crust and the solidified uppermost part of the mantle. Below the lithosphere lies the asthenosphere which comprises the inner viscous part of the mantle. The mantle behaves like a superheated and extremely viscous liquid.
212109
Apparently there is believed to be none now, but there may have been in the past.  Here is a quote from the link below:\n\nObservations of the magnetic fields on Mars by the Mars Global Surveyor spacecraft have revealed that parts of the planet's crust has been magnetized. This magnetization has been compared to alternating bands found on the ocean floors of Earth. One interesting theory, published in 1999 and reexamined in October 2005 in a publication by the same group, is that these bands could be evidence of the past operation of plate tectonics on Mars. However, this has yet to be proven or widely accepted and remains an area of active research.
710689
It does not help.  It is the LACK of sufficient conduction in the mantle that forces the core to get rid of its heat by mantle convection instead.  If the mantle conducted better, it wouldn't need to convect, and then there would be no plate tectonic movement at all.
918766
It does, but the Earth's magnetic field strength is very weak so the resulting emf is too small to be noticed.\n\nThe strength of the field at the Earth's surface ranges from less than 30 microteslas (0.3 gauss) in an area including most of South America and South Africa to over 60 microteslas (0.6 gauss) around the magnetic poles in northern Canada and south of Australia, and in part of Siberia.\n\nSo let's assume that we have a simple setup that can induce an EMF from Earth's magnetic field:\n\nEMF = -dΦ/dt, where Φ is the magnetic flux\n\nIf we consider a very simple case where Φ = BA, where B is the magnetic field and A is the surface area. So let's assume that\n\nB = 60 microTesla = 60 x 10^-6 Tesla or 0.00006 T\nA = 1 square meters\n\nand let the time duration of the manetic flux change be = 1 sec\n\nThen EMF = |-dΦ/dt| = BA/t = (0.00006)(1)/(1) = 0.00006 Volts\n\nAs you can see, I had to let the area of the magnetic flux be rather large (1 square meters). To see any sizable effect, we would actually need to consider much much bigger area, maybe like a square kilometer.