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 mantle is roughly 1,802 miles thick and consists of four layers: the lithosphere, the asthenosphere, the upper mantle and the lower mantle. The layer closest to the surface of the Earth is the lithosphere, and the rock there is very similar to that of the crust. The layer closest to the core is the lower mantle, where the rock is the most dense and hotter than the rest of the mantle.