National Geographic : 1948 Sep
Drawn byHarry S.Oliver and Irvin E.Allehnan New-foundUndersea Mountains Yielded Telltale Rocks and Sediments calm of the Horse Latitudes where good work ing conditions couldbeexpected. To get acquainted with themysterious world of mountainsbeneath these waters, we first made a seriesof runs back and forth across the Ridge withour Fathometer probing its hidden contours. Would the Ridgebejust achaos ofpeaks or would it follow some understandable pattern? Upon theanswer tothis question much of the successof ourexpedition would depend. At first the topography seemed thewildest confusion, but as westudied more and more profiles a definite pattern began toemerge. We found that we were able topredict when certain types of bottom would beencountered. For instance, on the flanks of theRidge strangely flat terraces were often followed by abrupt upwardslopes. A steep slope, where sediments could not accumulate, seemedthe most promising place to get rocks. For the first attempt Ichose theslope of a steep hill whichrose more than half a mile from a depth of1,900 fathoms, orabout two miles. Decks had been cleared for action by throw ing overboard the cramping deckload ofnow empty oil drums, and we unlimbered our"big gun," the deep-sea rock dredge (page 282). Groping for rocksindeep water with a metal bag on the end oftwo orthree miles of wire stands out asone of thehardest tasks of the submarine geologist, even when he attempts only to hitbottom atrandom. Because ofwinds and currents affecting the ship, thewire does not godown vertically. Hence, alength ofwire considerably greater than thedepth ofwater must beused. How much isneeded canonly beestimated. There isurgent need, which we hope tomeet, for adredge and trawl cable containing anelectrical conductor such asisused in"logging" oil wells. This would enable thedredge ortrawl tosend up automatic signals telling how deep itisand when ithits bottom. Iftoo much wire isputoutorifthe right amount isputout too quickly, theslack on thebottom may cause kinking, breaking thewire and losing theinstrument. Iftoo little wire isputout, thedredge fails toreach bot tom and allthetime-at least three orfour hours-is wasted. "Pinpoint" Dredging Two Miles Down Attempting tohitatarget with thedredge greatly increases the difficulties, since theship must remain stationary despite thecurrents and winds of theopen sea. The stories therocks can tell arehidden unless we know theplaces and elevations from which they come. Accordingly, Idecided totake what military men call acalculated risk and try "pinpoint" dredging. Well Iknew that anerror orwedging of thedredge insome rocky crevice below could mean loss of theequipment and aserious setback totheexpedition. Ifeltabit tense asIgave theorder tolower away. Lowering orraising thedeep-sea instru ments isanoisy aswell asexciting process.