Here Isaiah speaks various parts of creation as if they were people and commands them to praise Yawheh. (See: [[rc://en/ta/man/jit/figs-apostrophe]] and [[rc://en/ta/man/jit/figs-personification]])
"you lowest parts of the earth." Possible meanings are 1) that this refers to very deep places on the earth such as caves or canyons and forms a merism with "heavens" in the previous phrase or 2) that this refers to the place of the dead. (See: [[rc://en/ta/man/jit/figs-merism]])