CompuServe Messages

I managed to find the reference of the elemental composition of the earth's crust in Enclycypaedia Britannica under "Elements, Geochemical Distributions of." It lists the parts per million (or percentage) as, for example, Cobolt (25 PPM), Titanium (4,400 PPM), Aluminum (8.1%), etc. Seawater is Gold (1.0x10E-5 PPM) and Silver (3.0x10E-4 PPM). Seawater is also listed at 10.7% Hydrogen and 85.7% Oxygen–which seems odd to me because if the other data is in PPM in the same table, which would be the number of atoms out of million atoms, I presume; but the Hydrogen-Oxygen data suggests its by weight or volume, not atom-counts. Does anyone know how PPMs are defined in this regard? Anyway, I took this data and wrote the following: << . . . the earth is rich in resources; the trick is to know how to get them out. A cubic mile of backyard dirt, for example, contains enough aluminum to make a solid cube over 2,200 feet on each edge, and half again as much pure magnesium. As for "rare strategic metals," with the dirt left over one could fashion nine Great Pyramids of Giza of pure titanium, and nearly two more of cobolt. [NOTE: I calculated the Pyramid to be 96.3 million cubic feet.] Every cubic mile of sea water contains a cubic foot of gold, and nearly four [actually 3.5] of silver.>> I'm not sure I agree with my own calculations–especially the one about the aluminum as it seems pretty massive. I wonder if there is an error in my intrepreting the PPM (and percentages) as *by volume* whereas they were probabaly intended to mean *by weight*. If so, how can I convert the weight data to volume terms? I can probably look up the specific gravities of the metals somewhere, but it seems to me that I need to also know the the specific gravity of the earth's crust? Note that the earth's crust is primarily oxygen (47%), Silicon (28%), Aluminum (8%), Iron (5%), Calcium (3.6%), Sodium (2.8%), Potassium (2.6%), and Magnesium (2.1%). Any thoughts?