Geographical significance of sial and sima

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pohnpei397 | College Teacher | (Level 3) Distinguished Educator

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The geographical significance of sial and sima is that they are the two main parts of the Earth’s crust. 

Sima is a word that was created by merging the first two letters of “silica” and “magnesium.”  It is called this because its rocks contain a great deal of magnesium silicate.  Sima is the bottom layer of the Earth’s crust.  It makes up what we typically call the oceanic crust.  It rests on top of the Earth’s mantle.

Sial  is also a word made up from other words.  It is made up of the words “silica” and “aluminum.”  Sial is the upper layer of the Earth’s crust.  It rests on top of the sima.  Sial can be anywhere from 5 km to 70 km thick.  It is also known as the continental crust.  All of the Earth’s continents are on sial.

So, the geographic significance of sial and sima is that they are the two main parts of the Earth’s crust.  They are the upper (continental) and lower (oceanic) parts of the crust, respectively.

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