Winter operations, 1970-1971 / John C. Ayers, Norbert W. O'Hara, William L. Yocum.

Figure 10(31) shows in the background a push of brash which became Ridge B
in the winter of 1969-70.
Along the eastern shore of Lake Michigan during the two winters of our
study two icefoot ridges have been the rule, though three have been indicated
in a few of our photographs. Marshall's storm icefoot in Lake Superior (Fig. 1)
appears to indicate four such inshore ice ridges in that icefoot.
Formation of the Frozen Lagoon
After establishment of the icefoot (during which Ridge B may occasionally
develop blowhole activity) there eventually arrives a set of brash (or flow ice)
which covers the lakeward side of Ridge B and becomes solidified by spray-cementing, direct edge-to-edge freezing, and/or by the freezing of interstitial slush
formed from snow wind-swept into the intervals between floes.
Figure 11(34) shows at left the nature of the frozen lagoon. At present
our evidence indicates that ice over the lagoon may have water below it.
Formation of the Outer Ice Barrier (Ridge C)
Shortly after the ice floes that make up the frozen lagoon have arrived and
solidified, their outer (lakeward) edge becomes subjected to wave action which
breaks off some parts and loads the surface of the remaining outer edge with a
burden of spray ice, iceballs, slush, and sand that we suggest thickens the
outer edge of the lagoon ice until it has become solidly grounded on the lake
bottom after which the height of the ridge increases.
This outer ridge we have designated for convenience of reference as Ridge C.
Figure 12(36) shows our concept of the basic eastern Lake Michigan shore ice
structure. Ridge A, in the right middle distance, is low, compacting, and sandy.
Ridge B, in the right foreground is higher than Ridge A and somewhat sandy. The
lagoon ice, at left foreground to center middle distance, is frozen brash. From
the left Ridge C extends to the right distance as a distinct line of conical and

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