Iliac crest pain is not that common in the general population, but it is frequent in older individuals, runners (and athletes in general), lower back pain sufferersâ¦ But that doesn`t mean âregularâ people like you and me can`t experience it from time to time!
The mantle is composed of iron-magnesium silicates, and the crust is composed of roughly 5 percent iron. All together, iron makes up an estimated 35 percent of the Earth's mass. Oxygen. Oxygen, the second most abundant element on Earth, is found mainly in the crust.
The outer most layer of the Earth is the crust, which varies in thickness from about 7-70 km. Below that is the mantle, which of made up of denser rocks than the crust. At a depth of almost 3000 km, you reach the core, which is made of iron and nickel and is even denser than the mantle.