You are great as you are.这一句as引导的是方式状语从句吗？you are后面为什么没有表语？as作成分吗？

As 句中是连词. 意思是 由于; 像，像…一样; 同时，当…时; 尽管; as you are 后面应该有个 great，但是as 前面已经用了great 就不用重复了。英语中同一个句子都不要重复用同一个词。
如果是方式状语的话，前面这句用 you look great as you are 比较符合逻辑。

as you are 可以看成成语，表示你的本来面目，eg.
come to meet me as you are，请不要打扮来和我约会。

Peru is a country onthe Pacific coast of South America. It has three main geographical areas: anarrow coastal belt; the Andes Mountains running parallel to the coast; andhigh, flat plains in the southeast. 介词短语on the Pacific coast of South America作定语修饰county中心词。现在分词短语runningparallel to the coast作定语修饰the Andes Mountains中心词，相当于which run parallel to the coast定语从句，其中running: extendin a particular direction(延伸)之意。形容词短语parallel to the coast作方式状语。