Figure 2 - Lunar vlocanic flows The origin of the moon is unknown. These galileo images show that volcanoes have been active for more than 2 billion years, but the youngest lava flows are about one billion years old. Some of the Moon's lava flows are more than 600 miles long, and are as thick as a football field is long. The lava flow form Mare Imbrium would stretch from Phoenix to Salt lake City. Scientists believe the low lying areas were flooded early in the Moon's history. Those flows are covered with material thrown out of impact craters. Other meterorites punched holes in the old flows, bringing new lava to the surface.