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:
“The gods are partial to no era, but steadily shines their light in the heavens, while the eye of the beholder is turned to stone. There was but the sun and the eye from the first. The ages have not added a new ray to the one, nor altered a fibre of the other.”
—Henry David Thoreau (1817–1862)
“I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I—
I took the one less traveled by,
And that has made all the difference.”
—Robert Frost (1874–1963)
“There is a relation between the hours of our life and the centuries of time. As the air I breathe is drawn from the great repositories of nature, as the light on my book is yielded by a star a hundred millions of miles distant, as the poise of my body depends on the equilibrium of centrifugal and centripetal forces, so the hours should be instructed by the ages and the ages explained by the hours.”
—Ralph Waldo Emerson (1803–1882)