It also builds. 它们还能造景

137. and they're still getting bigger
     它们仍在不断扩大
138. as each year rainwater eats away a little more limestone.
     因为每年雨水都会侵蚀掉少许石灰岩
139. But water in caves doesn't only erode.
     可是洞里的水不光只是侵蚀
140. It also builds.
     它们还能造景
141. This water is loaded with dissolved limestone
     这些水中含有溶解的碳酸钙
142. and when it meets the air in the cave
     当它与洞内空气接触时
143. some of that is deposited as a mineral -
     其中的一些就会沉淀为一种矿物

来自《行星地球 第一季 第四集 Planet Earth S01E04 洞穴》第 140 行