世界匪夷所思的自然现象:美国风帆石

When visitors stumbled upon scores of heavy stones that appeared to have moved across the dried lake bed of Racetrack Playa in California’s Death Valley National Park, leaving a tell-tale trail in their wake, scientists were baffled. How had so many boulders, some weighing 300kg, moved as much as 250m across this remote part of the valley, asks Quora user Farhana Khanum?

在加利福尼亚死亡谷国家公园，游客无意中发现几十块大石头在赛马场盐湖的干湖床上移动，留下神秘的尾波，科学家们也不知道如何解释这一现象。Quora用户法尔哈纳•哈姆问道，这些卵石中有的重达300千克，它们是怎么做到移动近250米到达峡谷的另一头？

Adding to the mystery, some trails were gracefully curved, while others were straight with sudden shifts to the left or right. Who, or what, had moved the stones? A slew of theories emerged, from magnetic fields to alien intervention to dust devils to pranksters.

更为神秘的是，一些痕迹竟然还有优美的弧度，还有一些痕迹是直线状，但伴有突然左拐或右拐的印记。到底是谁还是什么东西在移动这些石头？从磁场作用到外星人事件到尘卷风再到恶作剧，人们对此猜测不断。

It took a NASA scientist to crack the case. In 2006, Ralph Lorenz developed a kitchen table model using a small rock frozen in an inch of water in a Tupperware container to demonstrate ice shove, the phenomenon behind the mysterious sailing stones.

一位美国航空航天局(NASA）的科学家解开了谜团。2006年，拉尔夫•洛伦茨发明了一个餐桌模型——在保鲜盒里装一英寸高的水，放入小石粒并将水冰冻。用这个模型解释冰壅，神秘的风帆石背后的真相。

In winter, Racetrack Playa fills with water and the lakebed’s stones become encased in ice. Thanks to ice’s buoyancy, even a light breeze can send those frozen boulders sailing across the muddy bottom of the lakebed. Stones with rough bottoms leave straight tracks, while those with smooth bottoms drift and digress. Warmer months melt the ice and evaporate the water, leaving only the stones and their mysterious trails.

一到冬季，赛马场盐湖涨满了水，而湖床里的石头则被冰封起来。由于冰有浮力，即使是一阵轻风也能帮扶着冰冻卵石一直划过湖床的泥泞底部。底部不光滑的石头会留下直线划痕，而底部光滑的石头则会漂移，偏离原路。天气开始转暖时，冰雪消融，水汽蒸发，留下的只剩那些风帆石和它们神秘的移动轨迹。

Visitors can see these sailing stones in a few locations, including Little Bonne Claire Playa in Nevada and most famously, Death Valley’s Racetrack Playa.

在内华达州的小女仆克莱尔盐湖以及著名的死亡谷赛马场盐湖等地方都可以发现这些风帆石。