Clapeyron slope
The Clapeyron slope (also known colloquially with the English term Clapeyron slope ; after Émile Clapeyron ) describes the pressure - temperature dependence of phase transformations of materials, e.g. B. of mineral structures and is by the Clapeyron equation
Are defined. It is therefore determined by the changes in entropy and volume as a function of pressure and temperature.
In simple terms, this means that the transformation of a material from one phase to another, e.g. B. a solid in a liquid or a mineral from one lattice structure to another, at a given temperature requires a certain pressure and vice versa. In relation to the interior of the earth or another celestial body, this means that phase changes of minerals occur at a certain depth at normal ambient temperature. If the temperature changes, the location of the phase transformation shifts to a different depth, since the pressure is proportional to the depth. An important example in the earth is the phase transition of olivine to wadsleyite in the upper mantle, the Clapeyron slope of which is positive (about 2.5 MPa / K): in the normal mantle it lies in the earth at a depth of approx. 410 km, in colder regions of the Mantle and subduction zones, on the other hand, are somewhat flatter, in hotter such as mantle plumes, on the other hand, somewhat deeper.
The Clapeyron slope quantifies this process, i.e. indicates the amount by which the pressure changes per unit of temperature. The unit is Pa / K , M Pa / K is common for geomaterials .
Footnotes
- ↑ a b Craig R. Bina & George Helffrich: Phase transition Clapeyron slopes and transition zone seismic discontinuity topography. In: Journal of Geophysical Research. Vol. 99, 1994, DOI: 10.1029 / 94JB00462 , pp. 15853–15860 ( PDF; 598 kB )
- ^ Frank D. Stacey: Physics of the Earth. 3rd ed. Brookfield Press, Brisbane 1992, ISBN 0-646-09091-7
- ^ Don L. Anderson: Theory of the Earth. Blackwell Scientific Publications, Oxford 1989, ISBN 0-86542-123-4