Why is the upper layer of the earth s crust called the granitic layer and the lower layer called the

The earth's crust is divided into two layers, upper and lower. The chemical composition of the upper layer is mainly oxygen, silicon, and aluminum, and the average chemical composition is similar to that of granite, which is called granite layer, and some people also call it "silicon-aluminum layer". This layer is thin at the bottom of the ocean, especially in the ocean basin floor, and even absent in the central Pacific Ocean, and is an uncontinuous circle.

The lower layer is rich in silicon and magnesium, and the average chemical composition is similar to that of basalt, which is called the basalt layer, so some people call it the "silicon-magnesium layer" (another way of saying that the entire crust is a silicon-aluminum layer, because the aluminum content of the lower layer of the earth's crust still exceeds that of magnesium; The rock part in the upper part of the mantle has a very high magnesium content, so it is called a silicon-magnesium layer); It is distributed in both continents and oceans, and is a continuous circle. The two floors are separated by a Conrad discontinuity.

From the perspective of material composition, the earth's crust is divided into two layers: the upper layer is a silicon-aluminum layer, which used to be called a granite (mass) layer, which forms a discontinuous distribution on the earth's crust, which is only available on continents and is missing from the ocean floor. The lower layer is the silicon-magnesium layer, which used to be called the basalt (mass) layer, and this layer is distributed continuously, both under the continent and at the bottom of the ocean.

So the overall composition of the continental and oceanic crust is different, the continent is granitic and the ocean is basaltic

842 Silicon-aluminium layer The upper layer of the earth's crust, from the ground to the Kangla noodles (i.e., one of the subordination above the Moho surface.

class discontinuities), mainly composed of sedimentary rocks and granitic rocks, the chemical composition of which is oxygen.

O), silicon (Si), aluminum (Al) are the main, sodium (Na), potassium (K), also more. Sedimentary rocks refer to various types of sedimentary rocks that are unconsolidated or consolidated on the surface of the earth's crust. Granitic rocks, on the other hand, refer to rocks with an average chemical composition similar to those of granite and diorite-like rocks.

**The propagation velocity of the wave in this layer is similar to the velocity transmission velocity in the granite, so it is called the granitic layer. The thickness of this layer can be up to 40 km in mountainous areas, more than 10 km in plain areas, and significantly thinner in oceanic areas, where it is absent in the central Pacific Ocean. The silicon-aluminum layer is an uncontinuous circle layer.

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It's conventional, and there's nothing for why.