"Magma is like seltzer: It contains "Volatile gases" - H20, CO2, SO2, N2, CH4 and other dissolved gases."
Can you say rock candy?
The link is good and has pretty picture.
"Scientists prize the rocks returned by the US and USSR missions as relics of the raw materials (the 'primary magma') that built the Moon and Earth. Primary magma is like the DNA of geology, providing the code that enables scientists to decipher the evolution of planets."
"think of opening a can of soda that has been shaken. The magma is like the soda spraying out when you open the can."
"Basaltic magma is like the blood of the earth - it's what comes out when the earth's skin is cut the whole way through. As an eruption ends, the basalt "scab" heals the wound in the crust, and the earth adds some new seafloor crust. Because the magma comes out of the earth (and often into water) it cools very quickly, and the minerals have very little opportunity to grow. Basalt is commonly very fine grained, and it is nearly impossible to see individual minerals without magnification."
"One type of rock gets its start deep in the Earth in huge underground pockets. There, the rock is so hot that it melts. This molten rock, called magma, is like a soup of different minerals and elements."
"Magma is like the molten metal that gets literally poured into molds across the world in thousands of factories."
The first part of this analogy is pretty good. The rest, in the link, is not so great.
"The same substance emitted from a volcano is rhyolite, and characterizes the explosive Pelee-Krakatoa-St. Helens type of eruption. Actually, dacite is quite predominant at Mount St. Helens. The explosive nature of St. Helens is because the magma is like that of your mother's home-made fudge, as compared to the molasses-type magma emitted by the Hawaiian volcanoes. St. Helens eruptions are quite explosive because "the fudge" caps building pressures up to a point when all hell breaks loose."
"If the temperature of the rock is too cold, the magma is like peanut butter in a refrigerator," Kent said. "It just isn't very mobile. For Mount Hood, the threshold seems to be about 750 degrees (C) - if it warms up just 50 to 75 degrees above that, it greatly decreases the viscosity of the magma and makes it easier to mobilize."
METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.