Yes exactly ! At first I thought I had missed something while reading the article ! But it looks like I haven't.

The article does a nice job of explaining the 'roots' bit but says nothing of the stabilisation !! and I have no idea why the professional geologist did not comment on that part of the question at all.

Ciwan wrote: I have no idea why the professional geologist did not comment on that part of the question at all.

Probably because it made no sense to him and was unaware of the questioner’s ulterior motive.
The only thing that I could think of to comment on that part of the question would be that the continental crust is not stable as there are processes such as mantle plumes which enable the continents to be split apart by rifting. Nor does it stabilise anything it moves too as it gets pushed around as evidenced by the action of plate tectonics.
Also the very fact that mountains get built by continental plates crashing into each other and that the geological evidence is that tall mountains are very young features as they erode over time goes to show very little for the assertion of stability.
The assertion that mountains stabilise the Earth is therefore simply unsupported.

Haha Awesome. Thank You. I love it when the murky ideas in my head become clear. Thanks very much.

Spearthrower wrote:

Ciwan wrote:
I always thought the Earth's crust was stabilized (needs stabilizing since it is basically floating on Magma) by the nearly-uniform-equal pull of Gravity from all sides.

The crust is not floating on magma, nor is it really floating on anything.

The layer underneath the crust is called the upper mantle, and it is predominantly solid and rigid. The crust needs stabilising like the skin on an apple needs stabilising!

Is this the case? I have never heard that the mantle was solid, but mostly magma flowing slowly from the earth's hot core to the surface and back again (thereby pushing the continental plates around). If the mantel hadn't some viscosity it couldn't create mantle convection right?

True JoeB, and also in all the documentaries I've seen, they always show the Mantle as a very thick hot soup-like thing (Molten rock really), moving from the centre outwards then back in towards the centre (convention).

JoeB wrote:

Spearthrower wrote:

Ciwan wrote:
I always thought the Earth's crust was stabilized (needs stabilizing since it is basically floating on Magma) by the nearly-uniform-equal pull of Gravity from all sides.

The crust is not floating on magma, nor is it really floating on anything.

The layer underneath the crust is called the upper mantle, and it is predominantly solid and rigid. The crust needs stabilising like the skin on an apple needs stabilising!

Is this the case? I have never heard that the mantle was solid, but mostly magma flowing slowly from the earth's hot core to the surface and back again (thereby pushing the continental plates around). If the mantel hadn't some viscosity it couldn't create mantle convection right?

I don't really have any online references for this: just books on basic geology.

But the wiki link pretty much agrees with what's in my books:

http://en.wikipedia.org/wiki/Mantle_%28geology%29

The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core. Earth's mantle is a rocky shell about 2,900 km (1,800 mi) thick[1] that constitutes about 84% of Earth's volume.[2] It is predominantly solid and encloses the iron-rich hot core, which occupies about 15% of Earth's volume.[2][3] Past episodes of melting and volcanism at the shallower levels of the mantle have produced a thin crust of crystallized melt products near the surface, upon which we live.[4] Information about structure and composition of the mantle either result from geophysical investigation or from direct geoscientific analyses on Earth mantle derived xenoliths.

The top of the mantle is defined by a sudden increase in seismic velocity, which was first noted by Andrija Mohorovičić in 1909; this boundary is now referred to as the "Mohorovičić discontinuity" or "Moho".[10][13] The uppermost mantle plus overlying crust are relatively rigid and form the lithosphere, an irregular layer with a maximum thickness of perhaps 200 km. Below the lithosphere the upper mantle becomes notably more plastic

Ciwan wrote:Let's say there were no mountains on Earth, and it was all flat ground (talking about the stuff above sea level) .... How would that affect Earth's crust overall ?

During all of the Mesozoic, there were actually next to no considerable mountain ranges.