Two types of tide-linked lunar phenomena now exist: the so-called lunar transient events, short-lived changes in brightness or colour and obscurations in small areas of the Moon (the reported duration is typically from a few seconds to a few hours and the areas involved are usually a few kilometres or less in diameter); and the A- and B-type seismic signals relayed back from the Apollo 12 passive seismic experiment. The frequency diagrams of both the lunar transien t events and the seismic signals show strong peaks at perigee when the Earth is closest to the Moon, with a smaller peak at apogee (transient events and B-type signal only) and both have been attributed to endogenous causes.

Both sets of data appear to be linked to areas where cracks and rilles exist. The most likely interpretation of the two sets of observations is that they are complementary and that some sort of gas release and excitation (in the cases of the glows and colour changes) is involved.

Association of the lunar events with craters with seamed and cracked floors and with other crack systems is described. Only a few associated areas of the Moon-wide lineament systems have been noted, but the Apollo 12 seismometer signals seem likely to originate from the nearby system of parallel features in the Fra Mauro area. The case for possible gas volcanism is examined.