The earth is personified as an individual who opens its mouth. Of course, behind the earth acting in this fashion is the power of the ascended Christ (recall the declaration of Revelation 11:15). The exalted Christ has the earth under his feet (Revelation 10:2). So the earth as his servant steps up to protect his bride.
16 But the earth came to the help of the woman, and the earth opened its mouth and swallowed the river that the dragon had poured from his mouth.