Hi Guest. The Earth consists of many layers, the outer layer is the crust which is solid, it is called the continental crust it is between 0-40km thick. next comes the lithosphere, this is a plastic material rich in Fe Mg silicates and is from 0-70km thick. After that comes the outer mantle or asthenosphere, this is more plastic and containes Fe mg silicates rich in copper, gold and silver, this is from 70-250km thick Then comes the lower mantle, this is between 700-2900km thick, it is a highly viscous fluid and consits mainly of Fe, Mg, Ni silicates and oxides. The next layer is the outer core, it is between 2900-4980km thick, it consits of liquid iron and nikel. The last is the the inner core, it consists of solid Fe Ni, it is between 4980-6370km thick. The inner core and the lower mantle are heated by compression and residue heat from the formation of earth, within this there are movements like that of water within a kettle when it is heated, thus hotter material rises and cooler material sinks to be heated again. This movement of material within the earth give rise to eddy currents which in turn produses the magnatism we experience today. Spencer.
Hi Al. Various methods were used to verify the various layers that make up the earth. The scientists knew the weight of our planet by two things, first the place in the solar system and the earths gravitational pull. Next they used seismic tests to discover the depth of the various layers, the denser the layers the faster moves the shock waves through them. The crust of the earth is much lighter than the layers underneath, and the layers under the crust are lighter than the core. Thus as a peice of quartz sinks in water so does the iron sink in the layer under the crust, ie the further down you are from the crust the denser is the medium. Spencer.
Seismic waves travel at different speeds depending on the material through which they travel. They also reflect off boundaries between regions. Seismic events occur all the time and they are monitored by many stations all over the globe. By correlating times of arrival (seismic stations track time by means of atomic clocks, GPS signals, and other, very accurate means - down to the microsecond - and they're all synchronized to the same timebase), a picture of the layers through which these signals travel emerges, giving us a pretty clear idea of how the Earth is constructed. As more data are collected the picture becomes increasingly refined and, contrary to what you see in most science textbooks, the Earth is not composed of clean, concentric layers like an onion. The shape of the interior is "lumpy," for lack of a better term, and its shape changes over time. Parts of it are liquid, parts are solid, and there is even a sizable electric current circulating through the interior (giving rise to Earth's magnetic field, which is also changing).
Magma and Magnetism
Re: Magma and Magnetism
