Everyone knows that the city is the busiest! However, it is also very lively underground in the city.
Let's take a look at the subway extending in all directions and transport people from here to there. Under the river in the city, there is a very long river-crossing tunnel (sê i) where cars pass. There are more pipes. Wires, gas and water pipes are all underground. Below the city, there are hospitals (Y and y Yuàn), garages (ku) and amusement parks. ...
How's it going? Is the subway in the city lively?
Another explanation based on extended data;
The core is the core of the earth, located at the innermost part of the earth. The radius is about 3470km, and it is mainly composed of iron and nickel with high density. The average density of the core material is about 65438 00.7 grams per cubic centimeter. The temperature is very high, 6680℃.
Similar to other terrestrial planets, the structure of the earth is layered, and these layers can be determined by their chemical and rheological properties. The earth has a silicon-rich crust, a very viscous mantle, a liquid outer core and a solid inner core. These understandings of the internal structure of the earth come from physical evidence and some inferences. The evidence includes materials ejected by volcanoes and seismic waves.