Mackinac Falls
...that after the retreat of the Wisconsin glaciation, postglacial Lake Michigan used to drain through Mackinac Falls, which are now completely submerged under Lake Huron?
...that after the retreat of the <a href="./Wisconsin_glaciation" id="mwCbk" rel="mw:WikiLink" title="Wisconsin glaciation">Wisconsin glaciation</a>, postglacial <a href="./Lake_Michigan" id="mwCbo" rel="mw:WikiLink" title="Lake Michigan">Lake Michigan</a> used to drain through <b id="mwCbs"><a class="new" data-mw-i18n='{"title":{"lang":"x-page","key":"red-link-title","params":["Mackinac Falls"]}}' href="./Mackinac_Falls?action=edit&amp;redlink=1" id="mwCbw" rel="mw:WikiLink" title="Mackinac Falls" typeof="mw:LocalizedAttrs">Mackinac Falls</a></b>, which are now completely submerged under <a href="./Lake_Huron" id="mwCb0" rel="mw:WikiLink" title="Lake Huron">Lake Huron</a>?