Edible geology #1 – The Earth is like a peach… sort of
by e_e_evans PhD student
As I wrote the title of this post I was reminded of a quotation from the Quandary Phase of The Hitch-hiker’s guide to the Galaxy:
“Life… is like a grapefruit. Well, it’s sort of orangey-yellow and dimpled on the outside, wet and squidgy in the middle. It’s got pips inside, too. Oh, and some people have half a one for breakfast.” – Ford Prefect
We could probably mull over how serious Douglas Adams was being when he gave that line to Ford but food analogies are a common metaphor, and geology abounds with them. So here’s a simple one to start of with:
The Earth is like a peach.
The similarities
The ratio of skin to flesh to stone is very similar to the ratio of crust to mantle to core (more anon on that!)
The fuzzy exterior of a peach at that scale represents quite nicely the hills and valleys of the planet, as does the non-perfect spherical shape. (The Earth is not actually a sphere but bulges slightly at the equator).
The differences
The crust of the Earth is broken into tectonic plates not one perfect, connected skin.
The flesh of a peach doesn’t illustrate well the plastic, solid-yet-it-flows, fluidity of the mantle (even if you wait until the peach is so soft the juice goes everywhere!)
The stone, while a good rough analogue for the diameter of the core, doesn’t illustrate that the core is made up of a liquid outer and solid inner core.
It also doesn’t show the correct temperature, pressure and phase boundaries but then that’s just splitting hairs. What can someone really expect for comparing fruit to the entire Earth!
So there we go, next like you eat a delicious peach you can contemplate its beautiful similarity to the layers inside the Earth.
Post-script:
“MY LIT REVIEW IS GOING FINE! STOP BOTHERING ME!!!!… ahem… I mean, my lit review is going fine, why do you ask?” (current word count: approximately 1700 words… ~1000 of which are references… oh dear…)
References:
For more info and further food based Earth analogies including boiled eggs and onions:
http://www.education.vic.gov.au/school/teachers/teachingresources/discipline/science/continuum/pages/earthstruc.aspx
My Geology Note-blog 