Geosphere

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The geosphere is sometimes described as everything and everywhere that is hard. The geosphere is considered that portion of the Earth system that includes the Earth’s interior, rocks and minerals, landforms and the processes that shape the Earth’s surface. The Earth itself is not a perfect sphere. It is what is called an oblate spheroid, with a radius of 6,357 kilometers (km) from the Earth’s center to the North Pole and 6,378 km from the center to the Equator. Prior to advanced instruments and spacecraft, 17th-century scientist Sir Isaac Newton predicted a similar shape based on the effects of the Earth’s daily rotation and his studies of other planets. Geodesy (the study of the Earth’s shape) is a very important science, in that it is critical for helping us understand satellite orbits, create maps and navigate on the planet using devices such as the Global Positioning System (GPS).

The part of the geosphere known as the Earth’s interior includes a thin, 5- to 70 km-thick layer of oceanic and continental crust overlying an additional 6,300 km of rock and metals. The crust varies in thickness and density. Oceanic crust consists of a thin, maybe 5 km, layer of dense rock and continental crust consisting of less-dense, lighter-colored rock ranging between 30 km to 70 km in thickness. Although the crust is comprised of many types of rocks and hundreds of minerals, these materials are assembled from a very small number of elements. A total of 98.7% of the crust consists of just 8 elements, including oxygen (46.6%), silicon (27.72%), aluminum (8.13%), iron (5.00%), calcium (3.63%), sodium (2.83%), potassium (2.70%) and magnesium (2.09%). These elements form the building blocks of most of the inorganic materials we encounter in our daily lives. Items such as glass (SiO2), concrete (CaCO3), and steel are formed from these materials. These minerals are often referred to as Sial. The oceanic crust is dominated by minerals consisting of silicon, oxygen and magnesium and is thus called Sima. The dense geosphere is also subdivided into the crust, mantle, and core. The outer core is unusual in that it is considered to be a liquid, yet it is a part of Earth’s interior.

The outermost portion of the geosphere is the crust. We walk on it every day. It hold our oceans in place, etc. Directly below the crust is the mantle. It consists of two parts, an upper layer that is less dense and relatively brittle and a lower, much thicker, layer that is more dense and more elastic in that it can deform without breaking. The crust and upper mantle combined form the brittle upper layers of the Earth’s interior called the lithosphere. The upper mantle is also called the asthenosphere.
The mantle makes up the largest volume of the Earth’s interior. The region beneath the mantle is called the core, and consists of two parts, a liquid outer core that is around 2250 km thick and a solid inner core 1220 km thick. The core is primarily made up of iron, with a small amount of nickel. The liquid iron in the outer core is particularly important in that it is the primary source of the Earth’s magnetic field. Almost all of our direct knowledge of the Earth’s interior is from the upper 10 km. Our knowledge of the remaining 6,300 km is based largely on indirect evidence from seismology, laboratory studies of igneous and metamorphic rocks, computer models and meteorites.

The geosphere is interesting to the point of spawning several different fields of study. We dig in, curse it when things do not grow, and use its minerals everyday. You could say that the geosphere is the stuff that our lives depend on. There is a great article on the different aspects for the geosphere at this url. Universe Today has a good article about the building of the most advanced map of the geosphere to date.

Tagged as: asthenosphere, Earth's crust, Earth's inner core, Earth's mantle, Earth's outer core, geosphere, sial, sima