Glowing lava in Hawaii. Image taken from Wikipedia Commons here.

def. Magma
1. Molten (liquid) rock below the Earth’s surface. Often contains volatiles, crystals, and small fragments of solid rock.
2. Not a synonym for lava, which is what you call magma after it has been erupted or extruded onto the Earth’s surface.
3. A favorite word of evil scientists, at least in Hollywood movies.

When non-geologists (and perhaps some beginner geologists) think about magma, there are two common mistakes that I have observed.

The first mistake is confusing magma with lava or treating the two words as synonyms. This is understandable as magma and lava are similar. Both are hot, molten rock. Both can contain volatiles (dissolved gases), crystals (that form as the molten rock cools), and fragments of solid rock (often picked up from the surrounding solid rock). However, magma specifically refers to molten rock located beneath the Earth’s surface while lava specifically refers to molten rock at the Earth’s surface.

Non-geologists might think it silly to have two words to describe molten rock. Perhaps this is true. Perhaps we should call all molten rock magma or lava or even coin a new word– I propose “molta”– that encompasses all types of molten rock. However, I’d argue that having two words to distinguish between molten rock below and above Earth’s surface makes sense. Having two words allows geologists to be specific. For example, in my previous post on komatiite rocks, I was able to say that komatiite rocks formed from lava that cooled. When I said that there is clear evidence that komatiites cooled from lava, geologists immediately understood that this meant these rocks formed at Earth’s surface. This is significant because komatiite rocks have a composition that is normally found deep within the Earth, not at Earth’s surface.There are also some differences between magma and lava. For instance, lava usually contains fewer volatiles (gases) than magma because these escape to the atmosphere.

Science is often intimidating and inaccessible to non-scientists because of all the vocabulary. When you become a scientist, you almost have to learn to speak a new language. While all of the vocabulary can be overwhelming until you learn it, science vocabulary exists for good reason. Science is all about being specific, about describing, quantifying, and– ultimately– understanding a part of the universe. Having a specialized, organized vocabulary allows precise classification. This vocabulary allows scientists to talk to each other and to compare finds and observations from different parts of the planet and universe.

One reason I write the geology word of the week is to explain and celebrate some of the remarkable vocabulary that geologists have developed to describe and classify their rocks. I love geology words. I love talking geology. But I realize that when I talk geology many of  my non-geologist friends are left in the dark. My best friend is an ocean engineer, so I have had to teach her some geology vocabulary over the years. She’s taught me some engineering vocabulary, and now we can talk– with relative ease– with each other about our research. Maybe on this blog I can teach some other people some geology words– and also teach myself some new geology words!

Of course, sometimes scientific vocabulary is a little too complex, even for scientists. For instance, there are thousands upon thousands of different names for rocks. The exact same type of rock might have a dozen different names. This is partly because rocks were independently “discovered” in different places and given different names. A rock might be called by one name in one country and by another name in another country. Rock and mineral names have been standardized internationally in relatively recent times, and continued standardization is an ongoing process. Unfortunately, the standard system of rock names isn’t perfect. Some of the complex names that remain are relics of the time before standardization and really should be replaced by simpler, more logical names. Furthermore, not all geologists stick to the standard names, at least not all the time. Some geologists prefer old names that have been “thrown out” and still use them, at least informally amongst each other. To really speak geology, you have to know  not only the standard names but also many of the non-standard names that are favored by some geologists.

Complex scientific vocabulary also causes problems when scientists want to talk to non-scientists or even to scientists in other scientific disciplines. I speak geology (or at least geochemistry, a dialect of geology), but I don’t speak biology. I also don’t speak physics or astronomy or proper chemistry, though I do know many words in these languages. If I need to collaborate with a physicist or a biologist, I first need to find a common scientific language. Scientists, myself included, often struggle to translate their science into plain English. I believe that it is very important for the general public to understand science and for scientists from different disciplines to be able to talk to each other. I’m not sure the best way to overcome the vocabulary problem, but I don’t think that throwing out all of the vocabulary is the answer. Personally, I don’t see a problem with using some jargon (maybe more when talking to other scientists and less in popular science writing) as long as you explain the terms you are using.

Anyway, I am rambling (which is okay since this is a blog), so let me now continue on to the second common mistake about magma. I think that many people (or at least the people who write bad geology movies) imagine the Earth as being full of magma. They imagine that the interior of the Earth is mostly molten rock or, as Dr. Evil of the “Austin Powers” movies would say, “liquid hot MAGMA.” This is far from the truth. Most of the Earth is actually solid, not liquid. Only one Earth layer (the outer core) is liquid. The Earth’s crust, mantle, and inner core are primarily solid. There is actually only a very small amount of molten rock compared to the amount of solid rock. Even the Earth’s asthenosphere (see last week’s word of the week if you don’t know what this is) is a solid, albeit it tar-like solid that moves very slowly over time. Molten rock only exists in small amounts in Earth’s crust and mantle. Furthermore, while there are some large bodies of magma in magma chambers and channels, much magma actually exists as tiny amounts in tiny pore spaces, not in well-defined magma chambers.

I think that understanding the words magma and lava is important because these words are so commonly used in popular science articles and even in every day life. Jessica Ball over at Magma Cum Laude wrote a great post awhile back about common mistakes made when reporting on volcanic eruptions. One of the mistakes she mentioned is that reporters often confuse magma and lava when writing about volcanoes. However, Jessica thinks it is important for reporters to use these (and other) terms accurately. I agree. Throw out jargon if you must, but don’t misuse scientific terms.

As a lighthearted example of the misuse of the word magma, I would argue that one of my favorite toys is misnamed. “Magmar” is a Rock Lords toy. The Rock Lords are similar to the more-popular Transformers toys except rather than being robots they are “powerful living rocks.” The Rock Lords toys were made in the 1980s, and I had a few of them as a child. Magmar is the leader of the evil Rock Lords. However, since Magmar exists on the surface of the Earth he should really be called “Lavar” or perhaps– since he is a rock– “Basaltar.” I didn’t appreciate Magmar’s misnomer when I was a child, but I do now as an adult geologist.

Magmar. Image taken from here.