the Earth's interior

   

   Last week I have talked about the geologic time of the Earth. As we know, the Earth have been survived through a very very long time and will be live longer. we are just living in the shorter hundred years,so what can I do? don't mind, that 's just my qustion.
    Do you know how big the Earth? Do you know what it is  under our feets? Do you know how the Earth work? I didn't know before I have studied it, and I am amazed by the Earth. It's so wonderful!  let us look inside the Earth together.
    
     First, the way to learn about the earth's interior is to dig or drill a hole and examine it. however, this is only possible at shallow depths. The deepest the drill has ever penetrated is only 12.3kilometers, about 1/500 of the way to Earth's center! Even this was an extradinary accomplishment due to the rapid increases in temperature and pressure with path.
   


      Seismic waves are used to probe Earth's interior. The pattern of seismic waves are complacted beacause their behavior is influenced by different structures. Seismic waves travel fast through cold rock and slower through hot rock. Seismic waves reflect of layers composed different merterials. The results of seismic imaging of Earth's interior can be interpreted through comparsion with mineral physics experiments. These expriments recreat tempretaure and pressure within Earth, and allow scientists to see what rocks and metals are like at various depths.(date from the book of <Earth>)


   second, Earth is layered with the densest mertierals at the center and lighest mertierals forming the outer layer. This layer is a result of gravity,and is similar for all planets. Earth layers consist of the inner core(solid iron), outer core(liquid iron),mantle(dense rock),crust(low-denisty rock), ocean(water), and atmosphere(gas). Within layers,
   
You can look the movie of  The details about the inside of the earth that can make you to understande easily.




 In addition, Earth's tempreture increases from about 0℃ at the surface to through 5500℃ at the center. earth became very hot early in his history,scince then, Earth has slowly cooled.
   Moreover,Earth is not perfectly layered. three-dimensional structures within earth have been identfied by studying variations in Earth's graviational and magnetic fields and imaging called seismic tomography.
  As you see, I can't  relate everything about the interior of the Earth. It is so big and complex, and there are lots of regions that humans can't reach to. I know that some microbes can live inside the Earth, but I can't image it! the environment is too bad to live, how can they live there?
    we can stand on here, we can get water and air, we can live here, because of the big planet. The Earth give us eveything, the place where we are is the only one.