488 A. W. G. WILSON SHORELINE STUDIES ON ONTARIO AND ERIE 



The reason why the flying spit was located just at this place on the 

 south shore of the lake it is a little difficult to find. There is a slight 

 change in the trend of the shoreline at the place where the barrier leaves 

 the mainland, but there are other localities east of this where present 

 conditions seem equally favorable and where no spit has been formed. 

 The amount of rock exposed at the bases of the cliffs east of this is 

 greater than here and the supply of waste would be less than at Erie. 



Sand dunes. — On nearly all the spits and forelands on the lake, belts of 

 low dunes have been built behind the beaches. In the majority of cases 

 these dunes are now stationary because of the presence of growing trees. 



Particularly along the north shore of the lake, however, there is another 

 type of dune that is of economic importance. Most of the sea-cliffs on 

 the north shore expose the raw edges of extensive beds of sand containing 

 perhaps a little gravel. At the bases of these cliffs the beach usually con- 

 sists largely of sand and is usually wide and of a low angle of slope. 

 Strong winds blowing shoreward create an updraft in front of the cliffs. 

 The upper air above the level of the crests of the cliffs continues to move 

 forward approximately in its original horizontal direction. At or near 

 the crest of the cliff, however, the updraft intercepts the horizontally 

 moving layers of air, and strong vortical whirls rotating inward are pro- 

 duced at the edge of the cliffs. Where the slope of the cliff face is not 

 too steep, the updraft carries great quantities of sand before it, and the 

 vortical whirl at the edge of the crest causes it to accumulate just behind 

 the crest. In this manner extensive dunes have been built up close to 

 the crests of some of the sea-cliffs. 



Numerous small, low dunes, of this type (20 to 80 feet high) occur 

 along the shore east of Port Eowan, notably near Port Colborne. Along 

 the cliffs west of Port Eowan there is also an extensive dune belt. In 

 Houghton township about 11% miles west of Port Rowan some very 

 large dunes occur. One of these rises about 120 feet above the edge of 

 the cliff and about 200 feet above the water. The north and northeast 

 face of the dune presents an even slope from base to summit and was 

 extremely difficult to ascend, as the sand has assumed the steepest angle 

 of repose and moves very easily. The crest line was very sharply marked. 

 At the crest the sand was quite moist and the adhesion was strong enough 

 to permit of the formation of overhanging edges in many places exactly 

 similar to the crest edges of a snowdrift. A few feet from the crest 

 toward the lake the moist sand was covered by about three-quarters of an 

 inch of dry sand. On the lee side, a few feet below the crest, the dry 

 sand was about three inches thick. Had it not been for the adhesion of 

 the moist underlayers it would have been almost impossible to ascend the 



