Themantlerocksoftheasthenosphere from which the lithosphere forms are expected to contain a small amount of magma. If the mass frac- tion of magma is 0.05, determine the depth of the lithosphere–asthenosphere boundary for oceanic li- thosphere with an age of 60 Ma. Assume L = 400 kJ kg−1, c=1kJkg−1 K−1, Tm =1600K, T0 =275K,and κ = 1 mm2 s−1.
The ocean ridges are made up of a series of parallel segments connected by transform faults. Because of the dif- ference of age there is a vertical offset on the fracture zones. Assuming the theory just derived is applica- ble, what is the vertical offset ( a) at the ridge crest and ( b) 100 km from the ridge crest (ρ m = 3300kgm−3,κ=1mm2s−1,α v =3×10−5 K−1, T1− T0=1300K, u=50mmyr−1).