Sitting at home I realized spots on the moon. I felt that there are some dents or scars on the moon. It made me suspisious . I searched on net about it and the conclusion I found was that millions of years back there was lava on the moon . So, if there is lava on the moon why doesn't it irrupt? Why is the moon white then?
Yes, there are several basalt seas A.K.A. "Lunar Mare" on the moon, these are some of the darker areas you see when you look at the moon. Basalt being a specific type of "rock" created by volcanic flows. I've read up some on it, as it's actually pretty interesting, well for a rock that is.
The lunar maria /ˈmɑːriə/ (singular: mare /ˈmɑːreɪ/)1 are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions.
There is no lava at present because the moon is small and has radiated most of it's internal heat to space at this time, also it's far enough away (from earth) that there is almost no tidal heating anymore (also this is due to us having only 1 moon and it being tidally locked.)
Internal structure of the moon.
in 2010, a reanalysis of the old Apollo seismic data on the deep moonquakes using modern processing methods confirmed that the Moon has an iron rich core with a radius of 330 ± 20 km. The same reanalysis established that the solid inner core made of pure iron has the radius of 240 ± 10 km. The core is surrounded by the partially (10 to 30%) melted layer of the lower mantle with a radius of 480 ± 20 km (thickness ~150 km). These results imply that 40% of the core by volume has solidified. The density of the liquid outer core is about 5 g/cm3 and it could contain as much 6% sulfur by weight. The temperature in the core is probably about 1600–1700 K
Mostly it's such bright white/grey because of bleaching by UV and solar radiation, no magnetic field, no atmosphere, slow rotation relative to the sun. Essentially it's baked by UV radiation, which has broken down most the "soil" on the moon. There is hardly any moisture or free oxygen to speak of so you don't get the pretty red of iron oxides, or much of any oxides.
Here is a bit more on lunar soil
There are two profound differences in the chemistry of lunar regolith and soil from terrestrial materials. The first is that the Moon is very dry. As a result, those minerals with water as part of their structure such as clay, mica, and amphiboles are totally absent from the Moon. The second difference is that lunar regolith and crust are chemically reduced, rather than being significantly oxidized like the Earth's crust. In the case of the regolith, this is due in part to the constant bombardment of the lunar surface with protons (i.e. hydrogen (H) nuclei) from the solar wind. One consequence is that iron on the Moon is found in the metallic 0 and +2 oxidation state, whereas on Earth iron is found primarily in the +2 and +3 oxidation state.