OUR PETROLEUM RESOURCES—PRATT 305 
-by seas at times in the past. Of this total area of former sea floors the 
rocks comprising about 6 million square miles are of a general charac- 
ter which make them of first-class promise for petroleum; they are 
present in great depth and are otherwise favorable for the occurrence 
of petroleum. The remaining area of 16 million square miles may 
also contain petroleum, but its general character is less promising and 
it is rated of secondary importance. 
Among other characteristics of sedimentary rocks Trask sought to 
determine the organic content. In this research he examined the rocks 
which constitute the floors of existing seas as well as those of former 
sea floors. The rocks from the floor of the deep ocean proved to contain 
but little organic matter. But rocks formed in seas, near shore, were 
found to be much higher in organic content. Of the rocks now forming 
on the floor of the Black Sea, for example, organic matter constitutes 
more than 35 percent by weight. In the rocks from the floors of former 
seas Trask found the organic content to range up to 10 percent by 
weight, averaging 1.5 percent. Trask estimated the average organic 
content of the rocks in the floors of all present seas at 2.5 percent by 
weight. 
Do these estimates promise enough organic matter to constitute 
source material for petroleum resources larger than we customarily 
reckon on? Let us confine our attention to the area of sedimentary 
rocks of first-class promise for petroleum, some 6 million square miles, 
excluding the remaining 16 million square miles entirely. Let us 
consider only that portion of the first-class area which is within easy 
reach of the oil man’s drill, eliminating all possible resources more 
than, say, 7,000 feet beneath the surface, despite the fact that a large 
proportion of our present supply of petroleum comes from greater 
depths. Let us apply to this restricted portion of the sedimentary 
rocks of first-class promise for petroleum only the average organic 
content estimated for the floors of all existing seas. 
Even on this minimum basis we obtain an estimated quantity of 
organic matter so large as to baffle comprehension—a quantity 200 
times greater in weight than the total coal resources of the earth! 
If only one-half of 1 percent of this organic matter had been con- 
verted into petroleum, concentrated and preserved for us in the 
natural reservoirs of the earth’s crust, our total petroleum resources 
would equal our total coal resources. If only one-tenth of 1 percent 
had been so preserved for us, our total petroleum resources would still 
be 60 times greater than all the petroleum we have so far discovered: 
that is, all our past consumption plus all our proved reserves. 
In view of these figures it is not unreasonable to suspect that the 
problem we face is not a dearth of petroleum in the earth’s crust so 
much as our failure to explore adequately and develop the resources 
