The concept of Mother Earth is an ancient one, appearing in many different cultures. One of the most famous is the Greek Gaia, mother to the Titans, the giants, and many others.
Obviously the myth-makers realized that nature has both good and bad aspects, which is why Gaia was the parent of monsters as well as the more pleasant aspects of the world. Hesiod described Gaia as “wide-bosomed,” which was pretty typical of ancient fertility goddesses, and of course a lot of people still do worship large breasts. Gaia is hardly the only Mother Earth figure in mythology, however. The people of the Andes, for instance, have long worshipped Pachamama, literally “Mother World.”
Apparently it was traditional to sacrifice llamas to her; and when the Spanish introduced Catholicism in South America, she became combined with the Virgin Mary. Slavic mythology gives us Mati Syra Zemlya, or Damp Mother Earth, who was apparently never personified but simply worshipped as the Earth itself.
Mother Earth figures were typically paired with Father Sky, as with Uranus in the Greek, presumably because the sky fertilizes the Earth.
Nowadays, the term “Mother Earth” is often used more or less interchangeably with “Mother Nature,” although nature is a more nebulous concept than the Earth. It seems to have come from Greek philosophy, basically used to encompass the entirety of observable phenomena, except for those deemed supernatural. In the Middle Ages, nature came to be seen as separate from the divine, as God is unknowable. Of course, we now know the natural laws governing a lot of things that the old philosophers would have considered supernatural. Anyway, if Wikipedia is to be believed, Mother Nature first emerged during the Enlightenment as a personified entity who was not divine, and female because God was male, I suppose. She was also popularized in the 1970s by Chiffon margarine commercials.
Really, considering that nature encompasses the entire universe, not just our own planet, wouldn’t Mother Nature be more powerful than Mother Earth? For some reason that doesn’t really sit right with me, even though it makes sense.