The tests used to determine whether brain stem death has occurred are outlined below: 1  A torch is shone into both eyes to see if they react to the light. 2  The cornea (transparent outer layer of the eye), which is usually very sensitive, is stroked with a tissue or piece of cotton wool to see if the eye reacts.
The inner core extends another 900 miles inward towards the center of the Earth. It is believed that this inner core is a solid ball of mostly iron, and nickel. The mantle is made of much denser, thicker material, because of this the plates float on it like oil floats on water.
The core of the Earth is the center. The inner core is solid, and is 90% iron. But the outer core is a liquid... and it's a good thing it is! More on that later. The outer core is made of a mixture of iron and nickel, with smaller amounts of silicon and oxygen. The outer core officially begins at a depth of 2550 km below the surface of the Earth, down to a final depth of 4750 km at the boundary between the inner and outer core.