Chihuahua Dog Breed. First discovered in Mexico, the Chihuahua is best known for being the smallest dog breed in the world. Extremely loyal to its owner, the breed has recently become a popular culture icon in the United States, most notably Paris Hilton's Chihuahua, Tinkerbell. Physical Characteristics.
Earth formed around 4.54 billion years ago by accretion from the solar nebula. Volcanic outgassing probably created the primordial atmosphere and then the ocean; but the atmosphere contained almost no oxygen and so would have been toxic to most modern life including humans.
As the Earth cooled, the water vapor condensed to form clouds, and the clouds rained down the water and created the oceans. The oceans on Earth formed around 4 billion years ago from water vapor that was accumulated in the atmosphere. Volcanoes spewed out many gases as well as water vapor.