Landforms

When observing the world’s topography, one sees the results, occurring over millennia, of  uplifts and erosions interspersed with advances and retreats of the world’s oceans.

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Helping to explain this and built on the concept of continental drift is the theory of Plate Tectonics. This theory describes 16 large and small rigid plates of the earth’s crust anywhere from 3 to 60 miles thick floating on the hot liquid mantle below. As our planet hurtles through space, these crustal plates run into each other, pull apart, run into each other time and again. The most famous of their unions was the super-continent, Pangaea.

What typically happens at the Plates’ conjoining is an Orogeny or mountain building phase, examples being the Himalayas formed by the butting of the Indian and Eurasian Plates, the Andes by the Nazca and South American Plate. When Plates pull apart the opposite happens. The earth’s crust is rent, ripped like taffy, one recent tear becoming the Atlantic Ocean. When earth’s Plates join or part, this contortion at the earth’s surface understandably creates opportunities for the mantle below to find weaknesses and bring its magma, molten rock, to the surface often in the form of volcanoes.

So volcanism as well as continental crunch is a player in mountain building. Among the present-day Rocky Mountains, formed during the Laramide Orogeny, there is an outlier in Colorado’s southwest corner, the San Juan Mountains. These are volcanic mountains comprised of some lava but mostly Welded Tuff formed during the Tertiary volcanic episode. Welded Tuff is hot ash that, when blown out of a volcano, falls and fuses as it lays then further solidifies as subsequent layers fall upon it. This is what the Easter Island Moai statues are made of and what buried Pompeii in 79 A.D. leaving corpses frozen in their agony. Following deposition, the Welded Tuff of the San Juans then saw as much as 5,000 feet of uplift giving rivers, streams and glaciers the power to create the landform we see today.

And so, unlikely to be found anywhere else in the Rocky Mountains, the Man from Welded Tuff appears high in the San Juans. With a wave of greeting, he makes his way towards us along a narrow cleft of rock looking like the mountain man, Bill Williams, for whom the creek below is
named.

He joins us every afternoon in shadow! 

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