Lunar domes are gentle undulations between 3 and 20 km in diameter, and at most a few hundred meters high. Most have very low angle of slope, only a few degrees at most. This makes the different domes of the Earth's volcanoes.

They are the best evidence of volcanic activity on the moon and many have a craterlet the heart that occurs after the cooling of magma and the collapse of the material to the bottom of the vent hole (creterlet these clearly visible in the photo!).

Granddaughters photo have some typical domes in Hortensius region that were reported in the rectangle, also can partially be seen almost in line with the terminator Milichius Dome of the arrow.

Domes probably formed in the latter stages of volcanism on the Moon, early-stage lavas are very fluid, due to its high heat, high volumes and mineralogy. This latter characteristic was particularly important as the lunar lava is mafic composition (has a low silica content and high content of metal oxide) tend to be very fluid (low viscosity). This is opposite to what occurs on earth where there is a high silica content, which produces steep domes. Because of this, the original lava on the moon flowed from eruptive fissures and did not produce volcanoes.

 Over time the lava were erupted cooling, reducing the flow rate and began to crystallize. That changed the lava characteristics, reducing its fluidity and starting to form a stack around its opening, leading to these low lunar volcanoes. This is the source of our lunar domes.

The distribution of domes on the lunar surface favors the western hemisphere of the moon with almost double the number of domes Eastern Hemisphere. The majority of the domes lie in the region of the seas. There is a large cluster of 28 domes in the region of Hortensius-Millichius-Tobias Mayer

Lunar Observation Summit

The observation of lunar domes is a challenging activity that requires dedication and good setup, coupled with good viewing conditions. The majority of the domes can not be observed when away from the terminator. With distance from the terminator and increased lighting angle of the dome of the profile will begin to mix with the local terrain and for all practical purposes the dome disappears from view. For the reasons mentioned, most authors recommend that the observations of the domes (and photographs) should be performed near the lunar terminator, where the solar altitude does not exceed 4-5 degrees. Other observers suggest 8 degrees of solar altitude as the minimum, but I've noticed that in more than 4-5 degrees of solar altitude, the smaller low profile domes and few surface details become less visible and almost impossible to photograph. There are only a few domes that can withstand high solar altitudes without disappearing in their local areas.

Lunar domes can be of various shapes and sizes, but the most common are hemispheric with a low profile, and sometimes a central craterlet. The craterlet is a good indication of volcanic origin of these structures, but is not always present. Domes without a craterlet still are of volcanic origin, but seem to have the central vent hole totally covered in lava.

Domes larger and more complex (Mega Domo) may have various surface features, for example Mons have Rümker which can be seen in my site http://astroavani.no.comunidades.net/mons-rumker

Sources: ALS THE LUNAR DOME SECTION - Guido Santacana and Eric Douglass American Lunar Society

              ALPO Feature: The Moon - Domes in the Hortensius Region - Raffaello Lena and others.

Adaptation: Avani Soares