The crust is the thinnest and the outermost layer of the earths interior this layer shows great variations in thickness and compossion. it is dived into two parts the contimental crust and the oceanic crust.
The continental crust is 30 to 50km thick it is chiefly composed of rocks rich with silicon aluminom (SIAL). granite is the basic type of rock that composed the continental crust.
The oceanic crust is comparitively thinner, being about 7.5km thicks. it is chiefly composed of rocks rich with silicon iron, and magnessium and magnesium (SIMA) basalt is the basic type of rock the composes this region of the crust basalt rocks are heavier and denser than granite rocks
marked chages in the way seismic or earthquake waves moved upon reaching a depth of 32 to 48km he observe using a seismogram that the seismic waves move much fast upon reaching such depth. mohorovic concluded that when compared to the crust, this zone differs in density cau causing in the earth quake waves travel faster. in recognition of his worthwhile discovery the rigid zone has been called the moho discontinuity a zone that seperate the crust and mantle
the mantle is the next year beneath the crust and the under the Moho. this layer reaches almost halfway to the center of the earth. the upper 965 km is upper mantle composed chiefly of silicates composed of and iron and magnesium the material/rocks in the mantle are denser compared to the materials in the crust. although this region is more dense, seismic waves travel much faster in the mantle than in the crust because the high temperature (3,000°C) and pressure (716 kg/cm³) cause the materials in the mantle to become elastic that is they yield to the passing of the seismic wave due to extreme pressure and temperature and then spring back without changing in form
the core is the innermost and the central region of the earth interior its extends to about 3,200 km from the mantle its temperature is about 3,038°C and has a pressure of three million atm analysis of the behavior of seismic waves revealed that core is divide into two distinct layers the outers and inner cores
the outer core extends from 2,880 km to 5,036 km from the mantle this layet is composesd of iron rich mental alloy and is inferred to be liquid in form.
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