Question

1. Airy Isostasy. Given a mountain peak having an elevation of 8000 meters, use Airy's isostasy theory to estimate the thickness of its "root" assuming an average crustal density of 2700 kg/m3 and that the rocks in the mountain are 10% less dense that the surrounding average crust. What is the total thickness from the mountain top to the bottom of its root in kilometers? How does this compare to the thickness of continental crust? Sea level Niveau de la mer - ------- - - bottom of root Base de la racine op-density contrast across bottom Op-contraste de masse volumique de part et d'autre de la base de la racine Fig. 1. Geometry of isostatic roots in Airy Heiskanen model. e - elevation density of topographic load, p. = density of water, Op-density contrast across bottom of root, d-depth to bottom of root, d, -depth to bottom of root at sea level elevations, d, -depth of water (after Simpson et al., 1986)

Answer 1

Amswer - Frooom the Army's hypothe sps. less than suroroouma rug moj - thiekness of the root, hy = height of the mouraim - 8000 cm. (elevarpon). Ju - Density of the migld upper layers. = 10% Is = Deusing of the lowero Layer = 2700 kg/cm3 Applying the valles pon eam (1) Crust = 2700-110 x 270e'= 27 100 = 2700-270 = 2430.kg/cm3 8000 X 2430 2700 - 2430 8000 x 2430 270 = 72000 m Toral distance from the top of the mountapm to the bottom of Pho root. Torce thickness = 8000 +72000mm = 80,000 m. = 80 kom. im general, the thieumess of the combinental ouust varies from about (35-40 urm) averoage value..