extends one third of the way around our planet. 便横跨了地球的三分之一

9. Grasslands exist wherever there is a little rain, but not enough to sustain a forest.
   草地无所不在 一点雨水虽然不足以维系一片森林 却可使一片草地存活下来
10. Some are huge.
    有些草原非常辽阔
11. The Central Asian Steppe alone
    仅中亚的疏树大草原
12. extends one third of the way around our planet.
    便横跨了地球的三分之一
13. It's summer, and eagles effortlessly cruise the thermals,
    在夏天 雄鹰可以毫不费力的在热气流上盘旋
14. scanning the ground beneath for signs of prey.
    搜寻地上猎物的踪迹
15. In the distant reaches of outer Mongolia,
    在遥远的外蒙古大草原

来自《行星地球 第一季 第七集 Planet Earth S01E07 伟大草原》第 12 行