Oceanic Mysteries


Lower Sea Levels

As has been mentioned, it is the concensus that Earth’s oceans supplied the moisture with which glaciers were built. No other source is suggested or apparendy conceived. According to this concept, the ocean level must have been lowered considerably during each glacial epoch. That ocean level has in fact very evidently been lower in the past than it is now, as cited as proof that the theory is correct.

Estimates vary as to the probable amount of regression of sea level supposedly caused by imprisonment of water in the ice. A low estimate of 70 meters is considered inadequate. Generally it is thought that the amount of lowering was about 200 meters. Dr. Francis P. Shepard in Submarine Geology suggests a possibility of 1,100 meters. Most geologists believe that the latter estimate is excessive. Yet, according to Veatch and Smith, there is definite evidence that the sea level was once as much as two miles lower than it is at the present—three times as much as anybody has estimated as result of glaciation!8

Of course, it is evident that the ocean level must have been recently raised by the melting of immense continental ice sheets. In fact, the process is continuing as of this moment, due to shrinking of remaining glaciers and ice caps. However, it is now generally doubted by glacier students that the volume of water involved in any ice age was anywhere nearly enough to account for the sea level being two miles lower than at present.

* Atlantic Submarine Valleys of the United States and Congo Submarine Valley; Special Paper #7, Geological Society of America, 1939.

Flint says sea level during the maximum of Pleistocene glaciation was not more than 120 meters lower than now. He labels an estimate of 276 meters by Ramsay as excessive. Professor Charles Merrick Nevin of Cornell, in Principles of Structural Geology, says: “there does Dot seem to have been nearly enough ice during the glacial period to account for a drop in sea level of several thousand feet.” While such doubts do not prove that glacial ice did not come from surface waters, they do definitely leave unexplained the greatly lowered sea levels which are known to have existed in past geological ages—levels as much as 10,000 or 12,000 feet lower.

At least four former terraces or strand lines have been found off continental platforms in several places around the world. P. H. Kuenan, in Marine Geology, states that Veatch and Smith showed the existence of an ancient “Franklin Shore” at 70 to 110 meters depth on the Atlantic Shelf of North America. He says:

Bourcart found three terraces, one below another, along the eastern Atlantic border, the deepest of which, at 500 to 1,000 meters, he judged to be of Mio-Pliocene age, one at 200 to 500 meters is supposed to be Upper-Pliocene, while the terrace at 0-200 m. is of composite age from Mid-Paleolithic to Recent.

All continental platforms are completely surrounded by gently sloping submerged land borders called continental shelves. They average about 100 miles in width and slope gently from shore seaward to an average depth at their outer edges of about 450 feet (von Engeln and Caster). Some writers say, 100 fathoms—600 feet. At the outer extremity of the shelves, the so-called continental slopes begin. With sharply increased gradients these slopes extend downward for some 12,000 feet to the abyssal ocean floors. Their slopes, in form and gradient, approximate those of rugged mountain ranges on land.

Submarine Canyons

Both shelves and slopes are furrowed by thousands of gullies, valleys and steep-walled “submarine canyons.” Many of the latter obviously are extensions of present river valleys. Some have tributaries with a dendritic pattern, just like those of river systems on land. They cross the shelves and incise the slopes, in some cases to a depth of 10,000 or 12,000 feet! The walls of the gullies and canyons in most instances are stratified, sedimentary rock, although in some cases they are crystalline, granitic, igneous rock. The upper strata contain fossils dated as late as Tertiary or even Quaternary.

Flint says that unconsolidated sediments on the continental shelves do not customarily grade from coarse to fine outwardly from shore as water-borne terrigenous sediments do. He points out that the sediments include wind-borne sand at depths of 180 feet. He interprets those and other characteristics as indicating that the shelves are of subaerial deposition and have been submerged only recendy. The deep gullies and canyons in the solid rock floors of the shelves and slopes point to long continued erosion preceding submersion.

Those who espouse the theory that oceans supplied the moisture for glacial ice ask us to believe that the shelves were temporarily exposed because water which formerly covered them was locked up in ice sheets. In order for the great amount of known erosion to have taken place during the interim, the shelves would have had to remain exposed for millions of years and the ice sheets would have had to endure for an equal period before beginning to melt and release water to submerge the selves again. This does not accord with the fact that glacial periods were of short duration. It is believed that all four stages of Pleistocene glaciation embraced less than a million years from start to finish. The last stage is thought to have been at its maximum a mere 25,000 or 30,000 years ago.

Certainly the lapse of time since then was far too short for rains and rivers flowing over the exposed shelves to cut the rock-walled gullies and canyons which exist in them; or for the detrital and fossiliferous remains to accumulate. In rebuttal, it might be argued that the shelves were exposed time after time during different glacial episodes; hence the erosions and fossils were cumulative results from successive short periods. That rivers which eroded the canyons would return to their identical previous locations after interglacial intervals of hundreds of thousands of years, to resume the interrupted erosions of the very same canyons, seems so improbable as to rule out the notion.