Ages
The ages of the mare basalts have been determined both by direct physical dating and by the technique of crater counting. The radiometric ages range from about 3.16 to 4.2 Ga, whereas the youngest ages determined from crater counting are about 1.2 Ga (1 Ga = 1 billion years old). Nevertheless, the majority of mare basalts appear to have erupted between about 3 and 3.5 Ga. The few basaltic eruptions that occurred on the far side are old, whereas the youngest flows are found within Oceanus Procellarum on the nearside. While many of the basalts either erupted within, or flowed into, low lying impact basins, the largest expanse of volcanic units, Oceanus Procellarum, does not correspond to any known impact basin.
Read more about this topic: Lunar Mare
Famous quotes containing the word ages:
“Ages when custom is unsettled are necessarily ages of prophecy. The moralist cannot teach what is revealed; he must reveal what can be taught. He has to seek insight rather than to preach.”
—Walter Lippmann (1889–1974)
“Let us praise his works beyond the ages and times, beyond eternity!”
—Jean Racine (1639–1699)
“Doubtless, we are as slow to conceive of Paradise as of Heaven, of a perfect natural as of a perfect spiritual world. We see how past ages have loitered and erred. “Is perhaps our generation free from irrationality and error? Have we perhaps reached now the summit of human wisdom, and need no more to look out for mental or physical improvement?” Undoubtedly, we are never so visionary as to be prepared for what the next hour may bring forth.”
—Henry David Thoreau (1817–1862)