What are some of the problems with an isostatic model of crustal ...

[mikaylakyoung]

What are some of the problems with an isostatic model of crustal elevations that relies on wood blocks floating in water as an analogy?
 
  What will be an ideal response?

Question 2

Explain two lines of evidence for how we know that mountains have roots.
 
  What will be an ideal response?

[juicepod]

Answer to Question 1

The wood-block analogy requires a very weak crust that breaks at the edges of blocks and the breaks go all the way to the base of the blocks. The upper crust is strong (not weak) and faults do not penetrate all the way to the base of the crust. The water analogy assumes a much lower viscosity than Earth's mantle.

Answer to Question 2

During the survey of northern India, a plumb weight did not point directly towards Earth's center but was deflected towards the Himalayas. The amount of deflection is consistent with the Himalayas having a thick crustal root. Seismic data also show that the crust beneath the Himalayas is thicker than the adjacent area to the south.