About This Item
Share This Item
Underwater study of oscillation ripples in nearshore sediments of Lake Michigan indicates grain size and subaqueous topography to be dominant controlling factors in ripple magnitude and development. Depth of water is not a primary factor in the formation of ripples in this environment.
With the use of self-contained underwater breathing apparatus (SCUBA), ripples were measured at 389 stations in eastern and southeastern Lake Michigan. Measurements of water depth, distance from shore, and of amplitude, wave length, and orientation of the ripples were made at each station. The ripples range in size from 2.5 to 38 inches from crest to crest. Those larger than 9 inches are found only in very coarse sand in the topographic lows. The smaller ripples are always present on highs and may also be found in deeper water.
Although only the nearshore shallow environment (up to 20 feet of water) was investigated, ripples are present in 36 feet of water more than one mile from the shore.
Ripple crests are normal to the general wind direction, although variation of as much as 60° in wind direction does not have noticeable effect on their trend. Great change in wind direction causes formation of interference ripples and subsequent change in ripple orientation. The trend of ripple crests approaches that of the shoreline as the strand line is approached.
Heavy-mineral concentrations are common on ripple crests, generally on the landward side of the crests.
Flat-topped ripples, heretofore described as being formed by planning off during falling tides or water level, are present in 8.6 feet of water. Incomplete ripples are common where till crops out on the lake bottom. Secondary ripples are common in many ripple troughs, particularly in the large ripples.
End_of_Article - Last_Page 523------------