1·These aquifers became saturated more than 10,000 years ago and are no longer being recharged.
这些含水层在一万多年前就饱和了，现在不再重新补充水分了。
2·Sandstones generally make good aquifers, while finer-grained mudstones are typically impermeable.
砂岩通常是良好的含水层，而细粒泥岩通常是不透水的。
3·Water does not remain immobile in an aquifer but can seep out at springs or leak into other aquifers.
水在含水层中并不是静止不动的，而是会从泉水中渗出，或渗入其他含水层。
4·Beneath the Sahara are huge aquifers, basically a sea of fresh water, that's perhaps a million years old filtered through rock layers.
撒哈拉沙漠下面是巨大的含水层，基本上是一片淡水的海洋，那可能是经过岩石层过滤的，已经有一百万年历史。
5·Anyway, it's this fossilized pollen along with the aquifers and the rock paintings, these three things are all evidence that the Sahara was once much greener than it is today.
总之，这些花粉化石，还有含水层和岩画，这三样东西都证明了撒哈拉沙漠曾经比现在绿得多。