248 
THE VOYAGE OF H.M.S. CHALLENGER. 
Many thousands of samples of terrigenous deposits have been examined from the 
shallower depths of nearly all oceans and enclosed seas. Of pelagic deposits more than 
2000 samples from depths exceeding 1000 fathoms — over 1600 from the Atlantic, 
300 from the Indian Ocean, and 400 from the Pacific — have passed through our hands. 
Even when the sample of a deposit has not been examined, the information furnished 
by marine surveyors and telegraph engineers is often sufficient to make known the type 
of deposit in the locality. The chart showing the distribution of the deposits, together 
with the following table, giving the approximate areas occupied by each type of deposit, 
have been constructed from a great number of reliable data, so that the broad outlines 
of distribution here presented are not likely to be much modified by future discoveries. 
The total area of the surface of the globe has been estimated at 196,940,700 square 
miles, of which dry land occupies about 53,681,400 square miles, and the waters of the 
ocean 143,259,300 square miles.^ In the following table the approximate extent of the 
areas of the sea-floor occupied by each type of marine deposit is given, together with 
the mean depth. 
Table showing the Mean Depth and the Estimated Area Covered by Marine Deposits 
on the Floor of the Ocean. 
Littoral Deposits (between tide-marks), 
Shallow-water Deposits (from low-water 
mark to 100 fathoms), 
Mean Depth in Area in Square 
Fathoms. Miles. 
62,500 
10,000,000 
Terrigenous Deposits (in 
deep and shallow water*/ 
close to land), 
Pelagic Deposits (in deep 
water removed from 
land), 
Coral Mud, 
7401 
2,556,8002 
Coral Sand, 
176 i 
Volcanic Mud, 
1033 1 
600,000 2 
Volcanic Sand, 
243 3 
Green Mud, 
513 1 
850,0002 
Green Sand, 
449 3 
Red Mud, 
623 
100,000 
Blue Mud, 
1411 
14,500,000 
Pteropod Ooze, 
1044 
400,000 
Globigerina Ooze, 
1996 
49,520,000 
Diatom Ooze, 
1477 
10,880,000 
Riidiolarian Ooze, 
2894 
2,290,000 
Red Clay, 
2730 
51,500,000 
• Murray, “ On the Ileiglit of the Land and the Depth of the Ocean,” Scot. Geogr. Mag., vol. iv. pp. 1-41, 1888 ; vol. 
vi. p. 26.^, 1890. 
* Tlicac areas differ from those given in the descriptions, in which are included deposits from the shallow-water 
zone. 
