英语听力：自然百科:黄石公园—夏天(5)（在线收听）

Calves born during the journey will be tested.

在旅途中出生的小牛将受到考验。

Clues to why the herds are drawn to the Yellowstone plateau lie in its deep and unique history.

究其牛群被吸引到黄石高原的原因，其线索就深埋在其悠久的独特的历史当中。

This plateau is the created bowl of a huge sleeping volcano.

这是一个巨大的休眠火山所创建的碗状高原。

And melting rock below the surface still pushes the land up to the cold of high altitude.

而且表面下的融化岩石仍将土地上升到寒冷的高海拔。

But it has not been the only force to shape the land.

但这也不是唯一塑造这片土地的力量。

Millennia ago,the volcano was covered by an ice sheet thousands of feet deep.

几千年前,这座火山被一个成千上万的英尺深的大冰原覆盖。

The few glaciers that border Yellowstone are an echo of a time when ice scared and smoothed the entire plateau.

当冰使整个高原变得平软光滑时，黄石公园的一些边界冰川是一种时间的回声。