core
Inside the Earth. The surface of the Earth is a thin crust about 6 km/4 mi thick under the sea and 40 km/25 mi thick under the continents. Under the crust lies the mantle, about 2,900 km/1,800 mi thick and with a temperature of 1,500–3,000°C/2,700–5,400°F. The outer core is about 2,250 km/1,400 mi thick, of molten iron and nickel. The inner core is probably solid iron and nickel, at about 5,000°C/9,000°F.
In earth science, the innermost part of the Earth. It is divided into an outer core, which begins at a depth of 2,900 km/1,800 mi, and an inner core, which begins at a depth of 4,980 km/3,100 mi. Both parts are thought to consist of iron-nickel alloy. The outer core is liquid and the inner core is solid.
The fact that seismic shear waves disappear at the mantle–outer core boundary indicates that the outer core is molten, since shear waves cannot travel through fluid. Scientists infer the iron-nickel rich composition of the core from the Earth's density and its moment of inertia, and the composition of iron meteorites, which are thought to be pieces of cores of small planets. The temperature of the core, as estimated from the melting point of iron at high pressure, is thought to be at least 4,000°C/7,232°F, but remains controversial. The Earth's magnetic field is believed to be the result of the movement of liquid metal in the outer core.
core
| In archaeology, a solid cylinder of sediment or soil collected with a coring device and used to evaluate the geological context and stratigraphy of archaeological material or to obtain palaeobotanical samples. Core can also mean the tool used to extract a core sample from the ground, or a stone blank from which flakes or blades are removed. |
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