Observing Project 5D Geological Forces at Work I The Marius Hills L42

The Moon as we see it today is geologically and volcanically dead. It is completely motionless through to the center of its core. Unlike Earth which is geologically very alive with shifting plates and a molten interior generating currents of molten iron and shifting powerful magnetic fields, the Moon is completely still. The Moon was not however always this way and certain features on its surface indicate with certainty that the Moon was once very active with a shifting surface and burgeoning fluid mantle.

Near the Moon's western limb, well to the south and the west of the lunar Alps, surrounding the crater Marius is a complex area of bulging hills which ring the crater on three sides known as the Marius Hills. In the Lunar 100, the hills are cataloged as L42. NASA strongly considered that area for the landing of Apollo 18 during the period of time before the Nixon Administration, when there still was an Apollo 18. The same types of disturbances created the Marius Hills in the lunar mantle that created the Badlands of North Dakota here on Earth. Magma pushing up from the liquid mantle below created bulges in the crust but could not push close enough to the surface to break through before the fluid rock hardened beneath the surface. These formations are called "volcanic domes" and are signs of the presence of an active fluid mantle long in the lunar past.

To find the Marius Hills, a good place to start is actually far away at a familiar place, the crater Copernicus, designated L5 in the Lunar 100. Look about 530km to the west into Oceanus Procellarum, where another prominent crater stands largely by itself. This crater is called Kepler and it is easily identified by a prominent ray system. From Kepler, go about 400 kilometers to the west-northwest across Oceanus Procellarum to find another solitary crater. We can make such large jumps across the surface here because large craters are in short supply in this smooth area of volcanic basalts. This crater is Marius and it too is easy to find because it largely stands by itself. Surrounding the north, west and south sides of this crater are the Marius Hills. The best observing time for the Marius Hills complex is when the Moon is approximately nine to ten days old and again when the Moon is about twenty-four days old just prior to local sunset.

The hills are softly rounded and dome shaped, suggesting that they were driven up from below. Note as you look through the area the absence of any sharp peaks such as what you saw when looking around Plato. The area surrounding the Marius region is largely flat which tells us there was not any other major mountain building force ongoing in that area. Marius stands alone, conspicuously sticking up in the middle of one of the Moon's largest volcanic seas. It is likely whatever force excavated Oceanus Procellarum left the crust beneath weakened to future volcan-ism. The once active mantle pushed magma up towards a weak spot driving up the hills. They are relatively shallow, only reaching heights of about 5,000 feet or so. The crater itself is about 40 km across and only about 5,000 feet deep. The walls of the crater support the hills to the north and west, but never caved in under the mountain-building processes. But in the northern hills, magma did break through to the surface. To the north is a very difficult to see channel called Rima Marius. At some point in the mountain-building process, it seems likely that magma did break through the surface and was channeled away by into the surrounding lava plain through this channel. Rima Marius is approximately 290 kilometers long and a maximum of 2 kilometers wide. More typically, the rille runs about 500 to 1000 meters wide.

So the Moon was once volcanically active with dynamic volcanic mountainbuilding forces, just like Earth. Did the Moon also once have active and moving crustal plates? Fault lines would indicate the presence of such plates. Does the Moon have any?

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