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.
Gravitational stresses led to extreme volcanism, and this is where Earth's first atmosphere came from. Contemporary volcanoes, however, do not expel the kinds of gases that most researchers believe must have been present in Earth's first atmosphere.xploring how Earth's atmosphere evolved and how life co-evolved with it. Earth's atmosphere is a complex self-regulating system that provides a protective envelope in which life thrives.