But most of the compounds found so far, say the doubters, come from volcanicdeposits.
怀疑者说，迄今发现的大多数化合物来自火山堆积物。
2
The clay deposits are scattered all over, in ancient volcanic surfaces and heavily cratered highland regions, some of which have apparently been exposed by erosion only recently.
粘土沉积分布在古代的火山表面和坑坑洼洼的高原地区，其中一些显然是最近才由于侵蚀而暴露出来的。
3
Now imagine that happening on an apocalyptic scale: millennia-long volcanic eruptions setting on fire--even exploding--massive coal deposits in present day Siberia.