flat valley floors的FLOOR是“地”还是“底”的意思?

问题描述:

flat valley floors的FLOOR是“地”还是“底”的意思?
It left Great Britain with mountains with flat tops,hanging valleys with flat valley floors,steep valley sides…

它为英国留下了平顶的山,陡峭而似绸缎般的瀑布、平坦的谷底、砾泥和肥沃的土地
floor应该是底