Traditionally, two main types of landscape — continents and the sea — stand out on the moon. The prevailing shape of the relief of the lunar surface is the lunar seas, which are huge in size basins of dark color. Of course, there is no water in these seas, but so these depressions were named in the distant past for their dark color; these names have survived to this day. Smaller dark spots, by analogy with the seas, received the names of bays, lakes and swamps. The main seas are concentrated within the visible hemisphere. The largest marine formation is the Ocean of Storms. Adjacent to it is the Sea of Rains from the northeast, the Sea of Humidity and the Sea of Clouds from the south. In the eastern half of the disk visible from the earth, a chain stretched from the northwest to the southeast of the Sea of Clarity, the Sea of Tranquility and the Sea of Plenty. The Sea of Nectar adjoins this chain from the south, and the Sea of Crisis from the northeast. Relatively small marine areas are located on the border of the visible and reverse hemispheres. These are the East Sea, the Regional Sea, the Smith Sea and the South Sea. On the reverse side, there is only one significant marine type formation — the Sea of Moscow. Irregular seas in most cases adjoin circular seas. The largest circular sea, the Sea of Rains, has retained only one of the outer rings in the form of mountain ranges of the Alps, the Caucasus, the Apennines and the Carpathians.
In addition to the seas, annular mountains are scattered over vast spaces, having a circular shape in the central parts of the visible lunar disk, and elliptical on the edge parts of the disk. The Ring Mountains are large and small circular formations, unevenly deepened, surrounded by ramparts that rise 0.5-1.5 km above the surrounding terrain. The ring mountains with a diameter of more than 35 km were called lunar circuses, and the rest — of smaller diameters — were called lunar craters. Small craters are located on the entire surface of the moon: on its plains, on the bottom of the seas, on mountain ranges and other formations.
Inside the circuses and craters, both on their bottom and on the slopes, there are so-called parasitic craters — formations of a later origin in comparison with the seas and the main system of ring mountains. For example, there is a large parasitic crater on the Phoebit crater, on the Katarina circus, Cyril, and several craters on the Thracastor circus. Often a conical mountain rises from the depths of the crater in the center. Having often not one peak, but two and even more.
You can meet mountain valleys, representing narrow long straight stripes stretching for tens of kilometers. Thus, the valley in the Alps mountain range is 120 km long and 10–15 km wide.
Typical formations are the lunar mountains, the height of individual peaks of which reaches 9 km, and mountain ranges that are similar to the earth and received by analogy the names of the earth mountain ranges of the Caucasus, Alps, Apennines.
Systems of various cracks and rays emanating from the bases of craters, furrows, and light rays are widespread. The total number of radiant craters visible on the full moon is about 300 on the side of the moon visible to us.
Sea and continental landscapes are located at different altitude levels. On the scale of the entire lunar ball, the difference in the average levels of the continents and the seas reaches 2.3 km. Within the visible hemisphere, this value is 1.4 km. The average level of circular seas is below the average level of irregular seas by 1.3 km and below the continents by almost 4 km.
The chemical composition and internal structure of the moon.
Samples of surface lunar rocks delivered to the Earth from the landing areas of the Apollo spacecraft and the automatic Luna station were studied in detail in terrestrial laboratories. Samples of crystalline rocks and soil were taken from seven sea regions of the moon and from two mainland. It turned out that the mineralogical composition of lunar rocks is very close to terrestrial rocks such as basalts, norites and anorthosites. The main rock-forming minerals, as on Earth, were pyroxene, plagioclase, ilmenite and olivine.
Of course, lunar rocks, with a general resemblance to terrestrial rocks, have their own significant differences. Lunar marine basalts are distinguished by a high content of FeO, and in some cases also TiO2. other basic oxides, SiO2, MgO, CaO, and Al2O3, are included in the composition of lunar rocks in approximately the same amounts as in the composition of terrestrial analogues of lunar matter.
Norites — non-marine basalts — are distinguished from marine basins by a higher content of aluminum oxides. Some samples of basalt and norite lunar rocks have a high content of potassium, rare earth elements and phosphorus. They got the common name of creep breeds (from the phrase KREEP-breed).
Anorthosites are the Earth’s analogue of the mainland substance of the Moon. These rocks practically consist of one mineral — calcium-rich anorthite. According to the degree of Al2O3 and CaO content, anorthosite rocks of the Moon are sometimes subdivided into actual anorthosites, gabbro-anorthosites and anorthosite gabbros. An external distinguishing feature of anorthosite rocks is their relatively high reflectivity.