The world has rarely been stable.
地球很少呈稳定状态
changing the climate,
改变气候
Pumping gases into the atmosphere,
向大气中排放气体
Throughout history, volcanoes have been one of the greatest agents of change.
纵观历史 火山一直是最大的变化因素之一
which leads to the third rule of life.
这产生了生命的第三条法则
So too is the battlefield itself,
战场本身也在不断变化
The Smilodon's mammalian cunning
刃齿虎作为哺乳动物的狡黠
Who will be the first to back down?
谁会率先退却?
Assessing the other's strength...
评估对方的力量
The two begin a ritual display.
两只鸟开始了一场仪式性的展示