Atmospheric dust was minimal throughout those five millennia until the mid-19th century, he says, but then, ‘from about 1860 to 1900, dust deposition rates shot up.’ This is surprising because usually dry means dusty, and the American West has almost always been dry – often drier than today. There was a near-permanent drought between 900 and 1300 which was so intense that it destroyed a series of native American civilizations, including the Anasazi, whose cliff homes are now US national treasures. Yet the evidence from the San Juan lakes is that it was not dusty. Even as their civilization was collapsing, the Anasazi seem to have protected their soils from erosion. This was not the case with the European settlers once they brought their cows. The landscape the cattle were introduced to was remarkably ill-equipped to cope with grazing animals, says Neff. ‘Unlike most other parts of the US, there were few grazers in the American Southwest until the Europeans came. No bison and few antelope or deer.’
📝 题目要求
找出文本中的逻辑关系词,并写出对应的逻辑类型
找出文本中的逻辑关系词；并写出所对应的逻辑类型：
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✅ 参考答案与解析
but：转折 because：因果 and：并列 so…that：因果 Yet：转折 Unlike：对比 but：转折（引出与之前尘埃极少相反的情况） because：因果（解释为什么尘埃增多是令人惊讶的） and：并列（连接两个相关事实） so…that：因果（表示极度干旱带来的结果） Yet：转折（对比前文的长期干旱与后问的并没有多尘） 6. Unlike：对比（引出美国西南部与美国大部分其他地区的鲜明对比）