SOURCE OF LUNAR BASALT
Lunar surface basalts are believed to have their origins in partially melted areas 100-400 kilometers (60-250 miles) beneath the large meteoroid impact basins. The basaltic material welled up into the basins through cracks created by the impacts. The basalt flows covered areas up to 1200 kilometers (750 miles) away from where they had arisen.

DISTRIBUTION OF BASALT
Basalt (shown in pink) is not distributed uniformly over the Moon. Nearly 26% of the near side of the Moon is basalt and only 2% of the far side is basalt. Most basalt in either hemisphere is found in areas of lowest elevation, particularly in the very large impact basins.

BASALT FLOWS
Distinct basalt flows overlap each other near a wrinkle ridge in Mare Imbrium. These lava flows are about 35 meters (115 feet) thick near their margins. The direction of flow was from the lower left toward the upper right corner of this photo.

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Racing to Space
The Moon decision
To reach the moon
Apollo 11
Later Apollo missions
What we learned about the Moon
After the Apollo Program


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Created: 7/99