Ocean Sediment Glazes by Joan Lederman. Plates Spread & Collide While Gulf of Mexico Evolves. Words written on back say, "Center of sea glass contains volcanic sand from Antarctica, Iceland and Hawaii is framed by Earth crust drillings (SPREADING) from mid-Atlantic Ridge framed by accretionary prism (COLLIDING) sediment. Tectonic plates." Back around foot says, "sediment glazes from Gulf of Mexico 1998 and 2009 . . . "