Natural Plates 55-95 km thick
Saturday, May 2, 2009

The earth is divided in nature plates. But how thick are they? New research shows that they vary in thickness from 55-95 km. Young oceanic plates are the least nature, the nature plate on the continents is the thickest.

Plate is the statement of position of the oceans and continents on Earth. The earth is divided in nature plates. The thickness of the character plates move on a softer mass has been long a subject of research. New research by an international team of researchers with thicknesses of 55-95 km. For this they used seismic data collected over fifteen years. The plate under the oceans is the least and has a sharp transition. The depth here varies depending on the age of that part of the plate. The older, the thicker. The research is published in Science.



The position and direction of motion of the character plates.
Causes


The transition is not only determined by temperature, but also by changes in the composition of the rocks. Also the (partially) melt, and the orientation of minerals play a role. This type of seismic waves changes react differently than a homogeneous mass of rock. The seismic waves slow down directly under the character sheet and travel quickly to the character sheet. The filtering of these data with various methods, the thickness of the plate in nature.
Lithosphere and astenosphere

The character sheets are also known lithosphere mentioned, or stone dish. This includes the crust and upper mantle of the nature. The underlying astenosphere is malleable rather than hard. The lithosphere moves on astenosphere towards subduction or mountain building.
Thickness

The thickness of the lithosphere under continents is in some places 95 km thick. In other places the thickness is 81 km. Also on islands in the ocean, the depth of the lithosphere-astenosphere transition determined as a result approximately 70 km. Because it is an island, it is possible to compare the thickness of the oceanic plate. Examination of Kawakatsu and colleagues shows that the thickness of the oceanic plate increases with age: 55 km thick at an age of 25 million years and a 82 km thick plate of 129 million years old. This is not surprising. After all, how old the plate, the more sediment can accumulate and then fossilize. Also cools a portion of the astenosphere and is part of the lithosphere.




A diameter of the earth. The lithosphere comprises the crust and the upper part of the mantle. © Creative Commons

References:

Romanowicz, B., 2009. The thickness of Tectonic plates. Science 324: 474-475.
Rychert & Shearer, 2009. A global view of the Litho-Sphere Astenosphere boundary. Science 324: 495-498.
Kawakatsu et al, 2009. Seismic evidence for sharp for Litho-Sphere Astenosphere boundaries of oceanic plates. Science 324: 499-502.


Source: kennislink.nl

Translated version of http://www.kennislink.nl/publicaties/aardplaten-55-95-km-dik