In the paper Evidence for basaltic volcanism on the Moon within the past 100 million years (Braden et al. 2014), suggest that features such as Ina (image below) represent a far more recent age of volcanism (relatively speaking, around 100 million years).

enter image description here

Image source: NASA Science News, where they have a different non-volcanic theory. However, this question is not about whether the features are volcanic or not.

From the Braden et al. article abstract:

The morphology of the features is also consistent with small basaltic eruptions that occurred significantly after the established cessation of lunar mare basaltic volcanism. Such late-stage eruptions suggest a long decline of lunar volcanism and constrain models of the Moon’s thermal evolution.

Assuming the latest models indicate volcanism as recent as within the 100 million years ago, what are the implications for lunar thermal history of younger volcanism?

  • $\begingroup$ The Wikipedia article cites studies suggesting volcanic activity as recently as 2 million years ago. $\endgroup$ Dec 10 '14 at 13:13
  • $\begingroup$ @JerardPuckett thank you for that, I don't use Wikipedia usually (I don't trust it) - but the Braden et al. peer reviewed paper does say within the past 100 million years, so I have fixed my statements to reflect this, but it does not change the main point of the question. $\endgroup$
    – user2449
    Dec 10 '14 at 13:33
  • $\begingroup$ Not an answer, but have you read about Kelvin and Perry and the heat modeling of the age of the Earth? americanscientist.org/issues/feature/… The Moon, smaller than the Earth, should cool faster and should have less heat of formation, but the lack of circulation would slow the cooling down pretty significantly. The Moon also should have similar amounts of radioactive elements to the Earth, which contribute to internal heating. Beyond that, the heat inside a large body like a moon or planet is pretty complicated. Above my pay grade. $\endgroup$
    – userLTK
    Apr 23 '16 at 7:59

A younger lunar thermal history implies that the Moon was still undergoing a contraction and cooling process, which was initiated when it began accreting material together. Evidence has shown that the moon has no tectonic activity, so all geologic features are volcanic.

The mare are a more recent example of this activity, and have been shown to have fairly young ages, as you indicated. The moon still has some internal heat from its formation that may be leaking out through convection and cooling.

Even though the moon has a relatively small mass, it didn't lose its internal heat as quickly as the earth because there was no tectonic activity to facilitate it fast enough, and convection is a slow process.

As the moon cools, it contracts, creating sharp ridges and cracks in the surface (see features known as 'scarps', or 'garden'). These contractions contribute to the "deposit" of material formed in the images that paper discussed. As the cooling surface shrinks, it breaks the crust through a thrust fault, which pushes some material higher and shoves other material lower.

Thrust fault causing a lobate scarp

What may appear to be river channels on the moon are also lava flows. These were initially underground lava channels whose roofs collapsed to expose these subterranean features. More recent incidents of molten material rising to the surface and cooling can contribute to some of the younger ages recorded in the basaltic rocks.

Cool lava tubes on the moon

Tldr; Evidence of younger volcanic activity confirms existing theories for the contraction and cooling process of the moon, just that it didn't end as soon as we initially thought


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