Newest questions tagged ocean-ridge lithosphere - Earth Science Stack Exchange most recent 30 from earthscience.stackexchange.com 2019-09-17T21:04:57Z https://earthscience.stackexchange.com/feeds/tag?tagnames=ocean-ridge+lithosphere&sort=newest https://creativecommons.org/licenses/by-sa/4.0/rdf https://earthscience.stackexchange.com/q/15746 3 Why is the Lithosphere-Asthenosphere Boundary an Isotherm? Benjamin Rogers-Newsome https://earthscience.stackexchange.com/users/14502 2018-12-10T22:09:58Z 2018-12-20T17:03:48Z <p>My understanding of the LAB is that it represents the point in the earth where the mantle undergoes a temperature activated mechanical change. The temperature of the boundary depends on the melting point of the mantle and so one could say that the LAB is an isotherm with temperature given by: <span class="math-container">\$\$T=kT_m,\$\$</span> where <span class="math-container">\$T_m\$</span> is the melting point of the mantle and <span class="math-container">\$k\$</span> is some constant.</p> <p>This is how I have had the situation explained to me, and in sources that I have read that the LAB is an isotherm at <span class="math-container">\$\pu{1300 ^\circ C}\$</span>.</p> <p>My only problem with this is that surely <span class="math-container">\$T_m\$</span> changes with depth, and therefore the Lithosphere-Asthenosphere boundary is not an isotherm at all, but depends on the depth at which the boundary is at (for example at a mid-ocean ridge where the boundary becomes shallower towards the ridge axis).</p>