Niagara Whirlpool
... that the Niagara Whirlpool formed when the Niagara River intersected an ancient pre-glacial river gorge?
... that the <b id="mwASE"><a href="./Niagara_Whirlpool" id="mwASI" rel="mw:WikiLink" title="Niagara Whirlpool">Niagara Whirlpool</a></b> <i id="mwASM">(pictured)</i> formed when the <a href="./Niagara_River" id="mwASQ" rel="mw:WikiLink" title="Niagara River">Niagara River</a> intersected an ancient pre-glacial river gorge?