Complex sentence: Above Grinnell Glacier is another glacier known as the Salamander which is an excellent example of a shelf or hanging glacier and was once attached to Grinnell Glacier, but both have retreated and are no longer connected.
Split into simpler sentences: Above Grinnell Glacier is another glacier known as the Salamander which is an excellent example of a shelf or hanging glacier. The Salamander and Grinnell were believed to be attached at one time, but both have retreated and are no longer connected.