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.
4.6 billion years ago. Earth begins to form as a ball of molten rock. 4.5 billion years ago. Volcanoes erupt gas and steam to form the oceans, and molten rock. 4.2 billion years ago. Earthâs surface cools and the hard outer crust forms. 3.6 billion years ago. The first continents form; life begins on Earth.