What is the average density of oceanic crust

The temperature in the inner core is about o C 10, o F , which is roughly the temperature of the surface of the sun section 3. Despite the high temperature that should melt these metals, the extreme pressure from literally the weight of the world keeps the inner core in the solid phase.

The outer core sits outside of the inner core. It has the same composition as the inner core, but it exists as a fluid, rather than a solid. The temperature is o C, and the metals remain in the liquid state because the pressure is not as great as in the inner core. The mantle has a density of 4.

The uppermost layer of the mantle is more rigid, while the deeper regions are fluid, and it is the motion of fluid materials in the mantle that is responsible for plate tectonics see section 4. Magma that rises to the surface through volcanoes originates in the mantle. The outermost layer is the crust , which forms the solid, rocky surface of the Earth. The crust averages km thick, but in some places, such as under mountains, the crust can reach thicknesses of up to km.

There are two main types of crust; continental crust and oceanic crust that differ in a number of ways. Continental crust is thicker than oceanic crust, averaging km thick, compared to km for oceanic crust. Continental crust is less dense than oceanic crust 2. The oldest rocks in continental crust are about 4. Finally, the two types of crust differ in their composition. Continental crust is made largely of granite.

This is because underground or surface magmas can cool slowly, which allows time for crystal structures to form before the rocks solidify, which leads to granite. Oceanic crust is mostly composed of basalts.

Basalts also form from cooling magmas, but they cool in the presence of water, which makes them cool much faster and does not allow time for crystals to form. Based on physical characteristics, we can also divide the outermost layers of Earth into the lithosphere and asthenosphere.

The lithosphere consists of the crust and the cool, rigid, outer km of the mantle. The crust and outer mantle moves together as a unit, so they are combined together into the lithosphere. The asthenosphere lies below the lithosphere, from about km to about km deep. The solid lithosphere is thus floating on the fluid asthenosphere.

To help explain how the lithosphere is floating on the asthenosphere, we need to examine the concept of isostasy. Isostasy refers to the way a solid will float on a fluid. Kirkpatrick, R. Anderson, R. Nature , — Hamano, Y. Google Scholar. Salisbury, M. Karato et al. DSDP Legs 69 , — Purdy, G.

Tectonophysics 47 , — Fountain, D. Article Google Scholar. Carlson, R. Cann, J. DSDP Leg 69 , — Becker, K. Raitt, R. Hill, M. Shor, G. Maxwell, A. Lewis, B. Download references. You can also search for this author in PubMed Google Scholar. Reprints and Permissions. Density of the ocean crust.

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