What is Structure of the Earth?
[[File:Earth-crust-cutaway-english.svg|thumb|250px|right|Earth cutaway diagram. The proportions are not accurate.]] The '''structure of the [[Earth]]''' is divided into [[layer]]s. These layers are both physically and chemically different. The Earth has an outer solid layer called the [[Crust (geology)|crust]], a highly [[wikt:viscous|viscous]] layer called the [[Mantle (geology)|mantle]], a liquid layer that is the outer part of the core, called the [[outer core]], and a solid center called the [[inner core]]. The shape of the earth is an [[oblate spheroid]], because it is slightly flattened at the [[geographical pole|poles]] and bulging at the [[equator]]. The boundaries between these layers were discovered by [[seismograph]]s which showed the way vibrations bounced off the layers during [[earthquakes]]. Between the Earth's crust and the mantle is a boundary called the '''moho'''. It was the first discovery of a major change in the Earth's structure as one goes deeper. #The '''[[Earth's crust|crust]]''' is the outermost layer of the Earth. It is made of [[List of rocks|solid rocks]]. It is mostly made of the lighter elements, [[silicon]], [[oxygen]], [[aluminium]]. Because of this, it is known as [[sial]] (silicon = Si; aluminium = Al) or [[felsic]]. #The '''[[Earth's mantle|mantle]]''' is the layer of the Earth right below the crust. It is made mostly of oxygen, silicon and the heavier element [[magnesium]]. It is known as '''sima''' (Si for silicon + ma for magnesium) or [[mafic]]. The mantle itself is divided into layers. ##The uppermost part of the mantle is solid, and forms the base of the crust. It is made of the heavy rock [[peridotite]]. The continental and oceanic plates include both the crust proper and this uppermost solid layer of the mantle. Together this mass makes up the [[lithosphere]]. The lithosphere plates float on the semi-liquid [[aesthenosphere]] below. ##Upper aesthenosphere: [[magma]] ##Lower aesthenosphere ##Lower mantle #The '''[[Earth's core]]''' is made of solid [[iron]] and [[n