The TOTO is a U-shaped, relatively flat-bottomed depression measuring approximately . Its depth varies gradually from in the south to in the north. This channel and the
Providence Channels are the two main branches of the
Great Bahama Canyon, a submerged geological feature formed by erosion during periods of lower sea level. During their early history the Tongue of the Ocean and the Providence Channel were broad, relatively shallow basins flanked by growing
carbonate banks. As the Blake-Bahama platform subsided, sedimentation kept pace with subsidence on the banks, but not in the basins. ==See also==