sand and gravel carried by the rampaging floods 挟带着砂石的湍急洪水

46. millions of tonnes of water
    百万吨降水
47. are dumped on the land in under an hour.
    在一小时内倾泻而下
48. Over millions of years,
    数百万年来
49. sand and gravel carried by the rampaging floods
    挟带着砂石的湍急洪水
50. have carved channels through the solid rock.
    在坚硬的岩石上切割出凹槽
51. Slot canyons, 150 feet deep.
    形成狭缝谷 深达四十六米
52. In some places, these canyons have widened
    一些地方的峡谷不断侵蚀扩张

来自《行星地球 第二季 第四集 Planet Earth S02E04 沙漠》第 49 行