Anticipating the next lunar eclipse on Friday, let’s see if lunar eclipses affect our Earth.

We’ll have the longest partial eclipse of the century on November 19, lasting 3 hours 28 minutes and 23 seconds, according to NASA. Lunar eclipses occur whenever the Earth, Sun and Moon are aligned and only on nights of full Moon. This eclipse will be visible in much of Europe and Asia, Australia, northwestern Africa, and North and South America. If you’re not able to watch the partial eclipse, there will be a livestream on the Virtual Telescope Project.

Do lunar eclipses affect earthquakes?

The Moon is known for influencing the Earth in a variety of ways. One of these ways is tides. Tides are a periodic and regular up and down movement of sea water caused by forces acting in the Earth-Moon-Sun system. The combined action of the gravitational attraction exerted by the Moon on the water mass and the centrifugal force that arises from the reciprocal movement of the Earth and the Moon in space generates tides. The Earth rotates around its own axis and, at the same time, the Earth and the Moon together revolve around an ideal axis, which corresponds in first approximation to the orbital motion of the Moon around the Earth. This means that in the space of a day the points on the Earth’s surface undergo the action of a force that varies over time.

Similarly to the Moon, the Sun also produces a tidal action which is however less effective due to the considerable Earth-Sun distance. On days of full Moon and new Moon, when the Sun, Moon and Earth are astronomically aligned, the tides have maximum intensity.

Despite there exists research of “a correlation between the Earth tide and earthquake occurrence that is closely related to the regional tectonic stress” (Tanaka, 2014), no evidence suggests that stronger earthquakes occur during eclipses.

Do lunar eclipses affect volcanic eruptions?

The problem with volcanic activity is that it is difficult to sharply state the exact time the condition for an eruption started (Girona and Huber, 2015). For some volcanoes research does exist on the relationship between eruptions and fortnightly (usual) tides, but it’s not extensive. There’s also research specific to full Moon tides that are known to affect certain volcanoes (see for example Fuego in Guatemala), and these will vary depending on location and type of volcano. 

Do lunar eclipses affect cyclones?

Interestingly enough, they do, similarly to earthquakes. In May this year, when cyclone Yaas was expected to make landfall in Bengal, disaster management experts were worrying that the eclipse could severely affect its impact. A landfall occurs when a cyclone impacts land after being over water. As explained above, tides are higher than usual on full Moon days, and cyclone’s winds produce water surges (or spring tides). The two combined can have a disastrous effect. If a cyclone makes landfall at the same time of the full Moon (and eclipse), a severe coastal flooding would happen, as the tides are higher and the winds blow seawater to the coast.

Do lunar eclipses affect floods?

To an extent, yes. Similarly to cyclones, if there’s a precondition for flood and water surges at the same timing as the full Moon, the higher tide will cause flooding near the river mouth.