介绍:
【读写课】Groundwater 第二段，详细内容请关注微信公众号(湖说英语)：stupidfrank
The necessary space is there, however, in many forms. The commonest spaces are ／those among the particles—sand grains and tiny pebbles—of loose, unconsolidated sand and gravel. Beds of this material, out of sight beneath the soil, are common. They are found ／wherever fast rivers (carrying loads of coarse sediment) once flowed. For example, as the great ice sheets (that covered North America during the last ice age) steadily melted away, huge volumes of water / flowed from them. The water was always laden with pebbles, gravel, and sand, known as glacial outwash, （that was deposited / as the flow slowed down）.
