Thursday, 10 July 2014

Penitentes

THESE AMAZING ICE SPIKES, GENERALLY KNOWN AS PENITENTES DUE TO THEIR RESEMBLANCE TO PROCESSIONS OF WHITE-HOODED MONKS, CAN BE FOUND ON MOUNTAIN GLACIERS AND VARY IN SIZE DRAMATICALLY: FROM A FEW CENTIMETRES TO 5 METRES IN HEIGHT. INITIALLY, THE SUN’S RAYS CAUSE RANDOM DIMPLES ON THE SURFACE OF THE SNOW. ONCE SUCH A DIMPLE IS FORMED, SUNLIGHT CAN BE REFLECTED WITHIN THE DIMPLE, INCREASING THE LOCALIZED SUBLIMATION. AS THIS ACCELERATES, DEEP TROUGHS ARE FORMED, LEAVING PEAKS OF ICE STANDING BETWEEN THEM.

Penitentes, or nieves penitentes (Spanish for "penitent-shaped snows"), are a snow formation found at high altitudes. They take the form of tall thin blades of hardened snow or ice, closely spaced with the blades oriented towards the general direction of the sun.

The Maelstrom When you hear a name like maelstrom, you just know it’s about something wicked. Introduced in English by Edgar Allan Poe from the Nordic languages, from which it came from the Dutch word maelstrom (maalstroom in modern spelling), it literally means crushing current, which is quite a very good description.


These odd structures really catch the attention, so much so I became curious and researched the mechanism behind their formation and whatever else I could find out about these strange formations. Interestingly they are first described in the scientific literature by Charles Darwin who encountered penitentes near the Piuquenes Pass in the Andes Mountains. Called 'snow cups' or 'penitentes' due to their resemblance to pilgrims or hooded religious figures the results can be startling in their strangeness. The pillars can be taller than a person, but the tallest I have seen on Mauna Kea this winter are about one meter, mostly just half a meter, I suspect they could be taller if given a chance, but that is the depth of the remaining snow fields.

 The conditions for forming penitentes have been present at the summit for the last couple months, and the process has been carving at the deeper remaining snow fields on the tops of the ridges and north sides of the pu'us at the summit. Currently entire snow fields of acres in size are carved deeply with these penitentes in the summit area. This has resulted in entire gardens of penitentes along the roads at the summit and another reason why the summit continues to be such a beautiful and fascinating place.

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