Discuss the processes on the moon that created the Maria, Highlands, and rilles

It was the result of a colossal impact onto the accumulating Earth flinging raw materials, forming the moon.

It took approximately one million years for the moon to form the Lunar Highlands. 3.9 billion years ago, a vast amount of asteroids and meteorites impacted the moon and reformed the it’s surface. Many people came to believe that at one time the moon’s surface was actually smooth, but when this bombardment of meteorites and asteroids occurred craters were formed. The lunar highlands are light in color, mountainous, and heavily covered with craters. The highlands contain the oldest rocks on the moon which are known as anorthosites, they are composed almost entirely of plagioclase feldspar with a calcium end group ( CaAl2Si2O8). Anorthosites seemed to have formed when feldspar crystallized and floated to the top of a global magma ocean that surrounded the Earth soon after it formed. So the highlands were most likely formed by the magma ocean.

The Maria, which contain many of the Moon’s largest craters called the basins, were most likely caused by the lunar cataclysm. The mare rocks are young compared to the highland rocks, being formed at approximately 3.3-3.6 billion years ago. They contain mostly basaltic rock- a rock with a high percentage of iron ( 17%-22% by weight) and a wide range of titanium (1%-

13% by weight) and a relatively low albedo as compared to the anorthositic highlands.

Rilles can come to be several kilometers wide and hundreds of kilometers in length. They are said to be formed from lava flowing above or under Earth’s surface, and are better known as “lava tubes”.

3 Types exist:

Sinuous Rilles- meander in a

curved path

Arcuate Rilles- have a smooth

curve and are found on the edge

of the lunar mare

Straight Rilles- follow a linear

path and are believed to be

grabbens- areas where the crust

has sunk between two parallel

faults.

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