Sial and Sima refer to the composition of Earth's Crust. The Crust is the uppermost layer and has different compositions for continental portion and the oceanic portion. The continental crust is rich in silicates and aluminum and hence is also known as Sial. The oceanic crust or the lower layer of the crust is richer in silicates and magnesium based minerals and hence is also known as Sima.
Earth's crust is composed of a number of pieces, also known as tectonic plates. Some of these plates consist of both the continental and the oceanic crust. In other words, these plates contain both sial and sima. Some examples of these plates are North American plate, African Plate, Eurasian plate, etc. A look at the map of Earth with these plates confirm the presence of sial and sima in these plates. For example, the North American plate consists of both the land and the ocean. It contains North America, Cuba, Greenland, etc. and a large portion of the Atlantic Ocean. Similarly, the African plate consists of most of the continental Africa and a large portion of Atlantic Ocean.
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