they march hundreds of miles across the parched plains. 它们在干涸的平原上跋涉几百英里
But on most tropical plains across our planet, the wet season is followed by a dry one. 然而地球上的绝大多数热带草原 在经历雨季后总是要经历旱季的
and will often trek vast distances across these parched plains 为了寻找绿洲
0ne and a half billion swarm across the savannahs of Africa. 以15亿的数量聚集在非洲的稀树大草原上
and the family will need to head out across the frozen sea before the mother's milk runs dry. 在母熊奶水干涸之前 一家人需要穿越冰封的海洋
Flocks 40,000 strong sweep across the frozen wastes. 4万只绒鸭飞越这一片冰天雪地的荒野
and they follow him closely as he travels across this desert 它们一起紧跟着它穿越沙漠
ancient rivers flowing across sandstone country steadily widen their canyons 古老的河流冲开岩壁 不断拓宽这些峡谷
These sand scenes can be hundreds of miles across. 这些沙漠布景可宽达数百英里
they came across whole galleries filled with the most unusual formations, 他们发现了成片叹为观止的地貌