In fact, this crust is quite rich in aluminum and calcium compared to Earth's crust. Earth's crust is split into two layers, the top being richer in aluminum silicates, "SiAl", with an underlying layer of magnesium rich silicates, "SiMg". However, the period between 4. The highlands geology is mostly composed of overlapping layers of material ejected from craters, predominantly the initial anorthosite aluminum rich crust.
Rocks brought back from the highlands vary in age between 3. Today's flat lowlands "mare" regions "mare" is Latin for "sea" formed about 4 billion years ago when immense asteroid impacts fractured the crust, allowing the lavas from kilometers deep miles to erupt through the impact fractures and form vast seas of lava. For comparison, Earth's crust today is 50 kilometers, or 30 miles, thick in most places.
This material was poor in aluminum and calcium, but rich in iron and magnesium. However, the lavas melted preexisting aluminum-rich surface materials and mixed with them. The lava was rich in the heavier radioactive elements which had initially settled well below the crust, and the radioactivity kept the molten seas of lava hot for millions upon millions of years.
Mare rocks have been measured to be between 3. The last molten lakes are thought to have finally solidified about 3 billion years ago. The resulting material which makes up the surface of these ancient lava seas is rich in iron and magnesium minerals, with a remarkably high content of titanium minerals. When you look at the moon, the mares are the darker areas, and tend to be circular in shape because they formed in giant asteroid impact spots.
It will help save life on our special planet -- be part of the solution in your generation. It will create and secure a better future for your children and grandchildren. It could be an interesting, cool, and a fun adventure for your life!
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Figure 2. To trace the detailed history of the Moon or of any planet, we must be able to estimate the ages of individual rocks. Once lunar samples were brought back by the Apollo astronauts, the radioactive dating techniques that had been developed for Earth were applied to them.
The solidification ages of the samples ranged from about 3. For comparison, as we saw in the chapter on Earth, Moon, and Sky , both Earth and the Moon were formed between 4. They are made of relatively low-density rock that solidified on the cooling Moon like slag floating on the top of a smelter. Because they formed so early in lunar history between 4.
The highlands have low, rounded profiles that resemble the oldest, most eroded mountains on Earth Figure 3a. Because there is no atmosphere or water on the Moon, there has been no wind, water, or ice to carve them into cliffs and sharp peaks, the way we have seen them shaped on Earth.
Their smooth features are attributed to gradual erosion, mostly due to impact cratering from meteorites. Figure 3: Lunar Mountain and Lunar Maria. Note the smooth contours of the lunar mountains, which have not been sculpted by water or ice. This view of Mare Imbrium also shows numerous secondary craters and evidence of material ejected from the large crater Copernicus on the upper horizon.
Copernicus is an impact crater almost kilometers in diameter that was formed long after the lava in Imbrium had already been deposited. Today, we know that the maria consist mostly of dark-colored basalt volcanic lava laid down in volcanic eruptions billions of years ago. Eventually, these lava flows partly filled the huge depressions called impact basins , which had been produced by collisions of large chunks of material with the Moon relatively early in its history.
The basalt on the Moon Figure 4a is very similar in composition to the crust under the oceans of Earth or to the lavas erupted by many terrestrial volcanoes.
The youngest of the lunar impact basins is Mare Orientale, shown in Figure 4b. Figure 4: Rock from a Lunar Mare and Mare Orientale a In this sample of basalt from the mare surface, you can see the holes left by gas bubbles, which are characteristic of rock formed from lava.
All lunar rocks are chemically distinct from terrestrial rocks, a fact that has allowed scientists to identify a few lunar samples among the thousands of meteorites that reach Earth.
Its outer ring is about kilometers in diameter, roughly the distance between New York City and Detroit, Michigan. It is located on the edge of the Moon as seen from Earth. What we do know is that the major mare volcanism, which involved the release of lava from hundreds of kilometers below the surface, ended about 3. The primary forces altering the surface come from the outside, not the interior. The surface is fine and powdery. I can pick it up loosely with my toe.
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