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 uppermost section of the mantle (see below), together with the crust, constitutes the lithosphere â an irregular layer with a maximum thickness of perhaps 200 km (120 mi). Many rocks now making up Earthâs crust formed less than 100 million (1Ã10 8) years ago.