Target Level: Elementary through middle school
Purpose: To learn about the stratigraphy (layers) of lava flows produced by multiple eruptions.
Background: Dark, flat maria (layers of basaltic lava flows) cover about 16 percent of the Moon's total surface. They are easily seen on a full Moon with the naked eye on clear nights from most backyards. The maria, quite similar to Earth's basalts, generally flowed long distances and flood low-lying areas such as the floors of big craters. Yet, the eruption sources for most of the lava flows on the Moon are difficult to find because they were buried by younger flows.
Generally, the overall slope of the land and local features such as small cliffs and depressions, influence the path of lava flows. Maps of the Moon show complicated lava flows, some in layers. The study of rock layers is called stratigraphy.
On the Moon, many older flows are covered by younger flows and become more pocked with impact craters. On Earth, old lava flows are usually more eroded and have more vegetation than young flows. Field geologists use differences in roughness, color, and chemistry to further differentiate between lava flows. They also follow the flow margins, channels, and levees to try to trace lava flows back to the source area.
Activity: This activity examines the patterns of lava flows produced by multiple eruptions. We use a short cup to hold the baking soda because we are looking at the flows and not at constructing a volcano model. Volcanoes, like those so familiar to us on Earth, are not present on the Moon. Three volcanic areas on the Moon include: the Aristarchus plateau, Marius Hills, and Rumker Hills.
Preparation: A baking soda-vinegar mixture and playdough are used to model lava flows. Different colors identify different eruptions. Students will be asked to observe where the flows traveled and to interpret the stratigraphy. Cover the work area and be prepared for spills!
In Class: This activity can be done individually or in teams. Making a vertical cut through the flow reveals the stratigraphy of the section.
Wrap-Up: Have students compare their layered lava
patterns of their classmates' patterns. Did they recognize
individual flows by color and outline? Point out how the oldest
flow is on the bottom of the stack. Each succeeding flow covers
older flows. The youngest flow is on top.
Purpose: To learn about the layers of lava flows formed by more than one eruption.
Vocabulary: eruption, source, stratigraphy
Materials: paper cups (4 oz. size, some cut down to a height of 2.5 cm); cafeteria tray or cookie sheet (1 for each eruption source); tape; tablespoon; baking soda; vinegar; food coloring, 4 colors; playdough or clay in the same 4 colors as the food coloring; soda straws; tooth picks; plastic knifes or something to cut playdough with (i.e. cardboard).