Did you know the moon is (sloooowly) shrinking?
There's a great tie-in with earthquakes and tectonic plates here. Unlike Earth with its many plates, the moon has only one continuous plate. When Earth's tectonic plates shift and move, energy can be released in smaller ways. Earthquakes, volcanoes, subduction, mountain formation, sea floor spreading - they're all part of the balancing act.
On the moon, the whole crust can only fold up into ridges when the core cools and contracts (think of the way an apricot forms ridges as it dries out and you'll get the idea 😂). The result of this rearrangement? Moonquakes that can last for HOURS. Can you imagine if earthquakes lasted that long??
Comparing the two spheres and their quakes might help your students understand the connection between earthquakes, energy, and tectonic plate movement.
For another connection, check out the two images below. On the first one, you can ask your students, which of the graphs represents the mass, volume, and density of the Moon as it shrinks, and why? The second image has the big reveal!
Spoiler below!
Once students made their initial predictions, I would ask them the following questions to go along with the graphs above:
💡What happens to the mass of the moon as it shrinks? Explain why you think this happens. The mass of the moon does not change as the moon shrinks. This means that all of the matter that composes the moon remains present (there aren't pieces of the moon breaking off) but is becoming more compressed as it shrinks.
💡What is volume? What pattern do you notice in the volume of the moon over time? Volume is the amount of space an object takes up. In the graph, the volume of the moon decreases over time.
💡What is the density of an object? Use the formula for density to explain the pattern shown in the graphs. Density describes how close the particles of an object are. It is calculated by dividing mass by volume. If the mass of the moon stays constant but the volume decreases, we are dividing mass by an increasingly smaller number. This would result in a greater density.
