I just had a great time talking with a first-grade class about volcanoes this afternoon – something that I love to do with kids of any age (and those who never really grow up, too). They came up with excellent, insightful questions about volcanoes and volcanic processes, and I was definitely kept on my toes when it came to answering. In fact, I definitely find it more challenging to talk to kids about geology than I do to adults, because kids are still learning about the world around them – they don’t necessarily have the background knowledge that an adult would, so I have to choose carefully how to explain things.

It’s not a matter of “dumbing down” my answers at all, but a matter of putting them into context. This is where geologic analogies come into play. I (and the rest of the geoblogosphere) love these, and we talk about them all the time – especially when they’re food based. But coming up with analogies that make sense to a first-grader requires some careful thinking (since I can’t exactly talk about high-proof liquor, much as I like Callan’s analogy for the continental crust). Here are a few that I’ve used in talks with younger audiences:

A volcanic eruption is like soda fizzing out of a bottle. This is a great way to explain the link between volatiles in a magma and eruptions, since volatiles are the main driving force. Most kids know what happens when you shake a bottle of soda (aside from getting in trouble with your parents), and a lot of them have seen the diet-Coke-and-Mentos experiment on TV. My advanced volcanology class just used that demo to illustrate eruption processes, so it’s good across all levels of learning.

Lava can be “runny” (like syrup or honey) or “sticky” (like toothpaste). It’s a little difficult to describe viscosity’s relationship to temperature and lava composition to younger kids unless you give them some analogues for lava types. Basalt is closer to maple syrup and can flow, while dacite or rhyolite is more like a big pile of crusty toothpaste. If you heat either of them up, they’ll flow faster; if you add bits (letting the syrup or honey ‘crystallize’, or put a lot of abrasives in the toothpaste), they flow more slowly. (Fun fact: Some toothpaste abrasives used at the dentist’s office are made from pumice – regular toothpaste uses hydrated silica or calcium carbonate.)

Volcanoes are built like layer cakes – or piles of dirty clothing. This is a simplification, but not totally unfounded. After all, Volcan Santa Maria (part of my field area) sure looks layered in cross section. This is true of some stratovolcanoes (and a few shields), but not all; that’s where the laundry pile comes in. Laundry piles can look fairly conical from the outside (especially if you cover it with a towel), but underneath they’re a complicated interlayering of lumpy, discontinuous bits of clothing (lava flows and domes). If you’ve got a laundry pile that’s been sitting around long enough to accumulate dust, that’s even better: you’ve developed some soil on those slopes.

Lava and water interacting is like rinsing off a hot cooking pan. If you value the flatness of your pans, this is something you’re not supposed to be doing, but let’s assume I’m talking about deglazing a pan instead. One question I got today was about what happens to lava in Antarctica when it hits snow and ice, and I expanded a bit to talk about what happens when lava hits water. Because of the huge temperature difference between lava and liquid H2O, contact between the two results in the instant boiling of the water and creates a lot of steam. In an above-ground setting, like the lava flow ocean entry at Kilauea, this is locally explosive but mainly just results in a lot of steam. But in an enclosed situation (groundwater encountering a magma body), this can cause large phreatic and phreatomagmatic explosions, forming features such as maars. (I skipped the maar part, but the pan analogy was a good way to emphasize that this is a pretty violent change of state for the water.)

Volcanologists are like detectives. Okay, this one isn’t strictly volcano-related, and it can apply to any branch of geology (or science in general). But it’s a good way to describe what geologists do: collect evidence about some event or process in order to work out what happened (or what’s going on). Sometimes this evidence can be as small as a few phenocrysts; sometimes it can involve a survey of an entire volcano. I love Sherlock Holmes stories, so I’m partial to this analogy, although I will admit that good old Holmes was only interested in geology so far as it affected the dirt on criminals’ shoes:

“Knowledge of Geology.—Practical, but limited. Tells at a glance different soils from each other. After walks has shown me spashes upon his trousers, and told me by their colour and consistence in what part of London he had received them.” –Dr. Watson on Sherlock Holmes’ limits, A Study in Scarlet

But Holmes’ obsession with detail is an important skill for a geologist; a geologic theory is the sum of a lot of details, after all.

I find that using analogies like these helps both me and the kids I’m talking to; they get to put an idea into a context that they understand, and I can assess how complicated my discussion can get before I start going over there heads. It also helps me build up a “presentation repertoire”; the more I do these sorts of presentations, the less thinking-on-the-fly I have to do (and the more I can rely on a stock of analogies that I know are reasonable and helpful for my audience).