Extraterrestrial lmpact and Megafauna Extinctions     About 13,000 years ago, near the end of a period called the Pleistocene, North America was populated by megafauna (...

Mars's Disappearing Atmosphere   For about the first billion years of its life, Mars was probably a watery planet. There are signs of past water in surface features, such as d...

题目： Carbon Dioxide Levels in the Ocean The concentration of carbon dioxide gas (CO2) is rising in the atmosphere, and some of this CO2 is taken up by ocean surface waters. To ...

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Reconstructing the Spread of the Grain Weevil Perhaps the most common, most widespread, and arguably most destructive pest of stored grain in history is the grain weevil Sitophilu...

The Early Iron Age     During the Bronze Age (roughly 3300-1200 B.C.E. in the Middle East), civilizations were limited in their use of iron. Most iron occurred not in ...

题目：     Prosperity in British North America     The British colonies of North America developed at a remarkable pace throughout the later colonial period. ...

Tidal Heating on lo     To understand tidal heating, we must go back to when the twin spacecraft Voyager 1 and Voyager 2 made close flybys of the moon lo, Jupiter's clos...

The Deforestation of England Today's typical English countryside of rolling green fields and few trees did not evolve naturally. England was originally wooded. Forests of oak and ...

Jazz   Jazz music, an art form original to the United States, originated in the southern city of New Orleans at the turn of the twentieth century. It combined the elements of ...