Why Canada Doesn’t Boil

By Ann Finkbeiner | September 9, 2010 | 2 Comments

Boiling

Heat rises, cold falls, and like a pan of soup on a hot stove, the earth boils, exceedingly slowly.  The boiling is called convection:  columns of heat rise from the earth’s hot core, move up through the viscous solidity of the mantle, cool at the crust, roll over and fall back down.  The crust that rolls along the top of the mantle is broken into continental plates which move with the boil, pushing up and apart where heat is rising, sinking under and down where the cold falls.  And thus the continents are recycled.  It’s all just physics.  But certain parts of the continents called cratons – places in, for instance, Canada, South Africa, Australia  – don’t recycle.  They just sit there while their plates move around them, they’re a couple hundred kilometers deep, they’re like stable keels, and how they manage the stability has been a mystery.

Rolling With the Boil

The answer turns out to be not terrifically sexy.  The roots of the cratons, the bottom of the keels, are lined with minerals that are unusually dry, and the more viscous mantle just flows around them.  This research was published in a recent Nature magazine and the editors liked it in spite of its unsexiness.  They said that the work was difficult, measuring the water content of tiny grains of minerals, pulling samples up from the continent’s roots; and doing both while making “a compelling scientific case marks a triumph for those involved,” wrote the editors.  “The work may not make headlines, but it deserves recognition.”

So here it is.  Let’s recognize it.

Photo credits:

Boiling (gold paint on convecting acetone):   WikiRigaou

Rolling with the Boil (Digital Tectonic Activity Map) (click on it, it’s gorgeous):  NASA

Comments

What’s that quote?

Science is first of all about discovery (the first word on
everything). But the more science knows, the more it realizes what it doesn't know (the last word on nothing). Curiosity and humility: the human condition.

Our Readers

What’s on the Banner?

It's an illustration from a display at the Field Museum in Chicago. It shows the different types of symmetry of life forms on Earth.

New Book: Siesta and the Midnight Sun

Now that humanity has spread right to the Earth's poles and adopted a 24-hour business day, our internal clocks struggle against our urban schedules. And the cost of ignoring these circadian clocks is high. The Exxon Valdez oil spill, Three Mile Island, the Bhopal chemical plant explosion, and the Chernobyl disasters were all attributed to human error and all happened on the night shift.

Jessa Gamble travels the planet to answer an essential question: Do we want to construct our own artificial timetables or find a new connection with the body's internal one?

Blogroll

• Bad Astronomy
• Bioephemera
• Centauri Dreams
• Cocktail Party Physics
• Cosmic Variance
• Deep-sea News
• Digging the Dirt
• Ecogirl & Cosmoboy
• Ecotone
• Elfshot: Sticks and Stone
• Laelaps
• NeuroTribes
• Not Exactly Rocket Science
• Rogue Classicism
• Speakeasy Science
• Spotty Dog
• Surprising Science
• The Loom
• The Sieve
• Tooth and Claw
• Universe Today
• Worldwatch Blogs