Labels:bannister | blister pack | book | bulletin board | cabinet | door | dropper | light | railing | sconce | vase | windowpane OCR: An Extraterestrial Impact, by Walter Alvarez and Frank Asaro and "What Caused the Mass Extinction? Volcanic Eruption by Vincent E Courtillot SCIENTIFIC AMERICAN October 1990] if IS remarkable that despite violent episodic perturbations the climate has been buffered enough to sustain life for3.5 billion years ATMOSPHERIC COMPOSITION shown by the relative concentration of various gases, has been greatly influenced by life on the earth The early atmosphere had fairly high concentrations of water and carbon dioxide and, some experts believe methane ammonia and nitrogen After the emergence of living organisms, the oxygen that is so vital to our survival became more plentiful. Today carbon CO NH ICH HO dioxide, methane and water exist only in BILLION YEARS AGO trace amounts in the atmosphere. AT ...
(.png)
