1. We walked to the furthermost point and then sat on the sand dunes. 我们走到了最远点，然后坐在沙丘上。
2. The sea may rise or the land may fall; either way the sand dunes will be gone in a short time. 海平面可能会升高，或者陆地可能会下降；不论发生哪种情况，沙丘都将很快消失。
3. Second, as you know, sand dunes contain other types of particles, besides sand, including clay and silt. 第二，正如你所知，除了沙粒，沙丘还含有其他类型的颗粒，包括粘土和淤泥。
4. Now, when the rain fell, water ran down the sides of the dunes, carrying clay and silt particles with it. 如今降雨的时候，雨水会带着黏土和泥沙颗粒从沙丘两边往下流。
5. They're up to a kilometer long, but only a few meters wide, and they're scattered along the desert floor, in valleys between the dunes. 我们所看到的石灰岩层高达一千米，而宽却只有几米，沿着沙漠底部和沙丘间的山谷分布。
