My favorite analogies, Part 2
In October of last year, I presented a list of my favorite analogies for geological processes. Effjot followed up with a visualization of one that was presented in the comments.
Today, I'd like to add to that list with three more evocative analogies.
Hydrothermal disseminated deposits are sweat stains.
Certain types of ore bodies are thought to be "sweated out" from magma chambers as they intrude to shallow enough levels in the crust. The shallow depths have low pressures, and that encourages the magma to devolatilize. The resulting hydrothermal fluids pick up lots of consitituents like sulfur and metals and stream away from the pluton. As they cool off, the dissolved constituents become supersaturated and begin to precipitate out as mineral deposits. These hydrothermal disseminated deposits end up in the pore spaces of surrounding rocks, or filling in cracks. This is kind of like how your body sweats out a solution of dissolved salts in water. When the water evaporates, the salts precipitate out wherever they find the space:
Sills are a funny kind of peanut butter sandwich.
A dike is an igneous intrusion which cuts across local stratification of the host rocks. Sills, in contrast, exploit the weaknesses between strata and inject their magma parallel to bedding. I think of this as being like using peanut-butter-in-a-tube to make a peanut butter sandwich without separating two pieces of bread. Like this three part series:
Exotic terranes are roadkill.
I show the following sequence of images to my Physical Geology students when discussing how exotic terranes accumulate on the leading edge of a drifting continent:
... and I think you get the idea. That one kind of speaks for itself...
How about you? Got any good analogies for relaying geological concepts?
Today, I'd like to add to that list with three more evocative analogies.
Hydrothermal disseminated deposits are sweat stains.
Certain types of ore bodies are thought to be "sweated out" from magma chambers as they intrude to shallow enough levels in the crust. The shallow depths have low pressures, and that encourages the magma to devolatilize. The resulting hydrothermal fluids pick up lots of consitituents like sulfur and metals and stream away from the pluton. As they cool off, the dissolved constituents become supersaturated and begin to precipitate out as mineral deposits. These hydrothermal disseminated deposits end up in the pore spaces of surrounding rocks, or filling in cracks. This is kind of like how your body sweats out a solution of dissolved salts in water. When the water evaporates, the salts precipitate out wherever they find the space:
Sills are a funny kind of peanut butter sandwich.
A dike is an igneous intrusion which cuts across local stratification of the host rocks. Sills, in contrast, exploit the weaknesses between strata and inject their magma parallel to bedding. I think of this as being like using peanut-butter-in-a-tube to make a peanut butter sandwich without separating two pieces of bread. Like this three part series:
Exotic terranes are roadkill.
I show the following sequence of images to my Physical Geology students when discussing how exotic terranes accumulate on the leading edge of a drifting continent:
... and I think you get the idea. That one kind of speaks for itself...
How about you? Got any good analogies for relaying geological concepts?
3 Comments:
I must be a bit twisted: I like the exotic roadkill terrane one the best.
Silver Fox, I strongly disapprove of accreting cute kittens onto large trucks. :-)
Still, the analogy works quite well! And more funny than my time-arm. So count me among the twisted…
Callan, do you mind if I use this post for the new Accretionary Wedge topic, Out of the Box teaching ideas? Lockwood mentioned it to me and I think it is a good idea.
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