Did you know that the Earth's Moon has seas on it? Actually, these are not seas but huge plains composed of basalt. Called the lunar maria or mare (pronounced as "ma-re"), these are formed from the volcanic eruptions.

Also caused by meteor and comet collisions, the Moon's surface is covered of about 16 percent of the maria. Other names though similar in characteristics are the oceanus, palus and sinus.

These are found on the other side and are smaller. But the largest of all the lunar maria is the Oceanus Procellarum.

Crater counting and radiometric dating are used to determine the age of a mare basalt. It has been found out that the ages of the mare basalts range from 3.16 to 4.2 Ga, where 1 Ga is equivalent to 1 billion years. The youngest of all, however, dates back to 1.2 Ga.

Distribution of mare basalts

Why it is predominant on one side of the moon is still being debated up to now. There is a suggestion that the distribution of the mare basalts on the surface of the moon is not caused by volcanoes since the eruptions happened only 500 million years.

Another explanation that became a misconception is that the Earth's gravitational pull has caused this since this is prevalent on the near side and not the far side of the moon. But that there is a difference in the centrifugal acceleration in the rotating frame of the Moon to the Earth, this is highly unlikely.

The composition of the basalts is based on the element chemistry they have. They are grouped into three: the high-Ti basalts, the low-Ti basalts and very low-Ti basalts.

Composition

Titanium is present in these three basalt types and less are found in the high-Ti basalts. Titanium oxide is also present in the mare basalts and reaches up to 15 wt. percent. Terrestrial basalts, however, only contain 4 wt. percent of them. Aluminum and potassium are also present in these compositions.