Education and
Public Engagement
at the Lunar and Planetary Institute
Explore! Marvel Moon

Teen Moon: Moon Ooze


Children model how the Moon’s volcanic period reshaped its earlier features.  The children consider that the broad, shallow impact basins — which had formed earlier while it was a “kid Moon” — contained cracks through which magma seeped up. Children use Rice Krispies Treats® to create a model lunar impact basin in a bowl in which slits have been cut in the bottom. A second bowl, filled with a small amount of chocolate syrup, is used to represent the pockets of magma within the Moon’s upper layers. When the model impact basin is pressed  into the “magma,” “lava” fills in the low areas through the same process that produced the dark patches, or maria, on the Moon. Children may examine a type of Earth rock (named basalt) that is also found on the Moon and that would have been shaped by the processes explored here. This station investigates the Moon’s “teen years,” when it was one to three billion years old.

What's the Point?


The following materials are for one Teen Moon: Moon Ooze activity set and will serve 10 children.
Two sets are recommended for a station:

For each child:

For the facilitator:



Described in the children's guide.


Once they have completed the experiment, the children should understand that the large, smooth, dark regions we see on the Moon formed billions of years ago when lava oozed through cracks in the lunar basins. The lava filled in earlier impact basins and solidified. Because the lava is younger than the light-colored regions, it is less cratered and looks smooth. Early astronomers mistook their smooth appearance for seas, and called the Moon's dark regions "maria" after the Latin word for "seas."

A Little Background for the Facilitator

The "teen" Moon bore the scars of an earlier period of intense bombardment, which left behind large, cracked basins across its face. While cool on the outside, portions of the Moon's interior were still hot, heated by radioactive decay of unstable isotopes of elements, such as uranium and thorium, and the processes of accretion and differentiation. Isolated pockets of hot mantle material slowly rose to the surface, melting at lower pressures. This magma poured out through cracks in the lunar surface — fissures — many of which were created by the earlier impacts. The magma flooded across the lowest regions on the lunar surface to fill the impact basins. It crystallized quickly, forming basalt, a dark, fine-grained, volcanic rock. The large, smooth, dark regions we see on the Moon are the basaltic "lunar maria." "Maria" is Latin for "seas," as these areas looked like seas to early astronomers. They are smooth because they are less cratered than the lunar highlands. The smaller number of craters in the maria suggests that these regions have not been impacted as much and therefore are younger. Mare basalts have been radiometrically dated to be between 3.0 and 3.8 billion years old.

Imagine standing on the Moon at this time. Hot basalt lava flowed from long fissures, filling regions of low elevation. Fountains of lava sporadically erupted along the fissures, spewing molten rock high above the lunar surface. Chilled magma droplets fell back as beads of colored volcanic glass, later sampled by Apollo astronauts. Flowing lava cut channels into the landscape. In a few locations, small volcanic domes built up on the surface of the maria. Gradually, as the Moon’s interior cooled, volcanism ceased. Lunar volcanism decreased significantly by 3 billion years ago and ceased completely by about 1 billion years ago as the interior cooled.