The Architecture of a Cirque

A cirque is the building a glacier left behind. The headwall is the vertical face the ice carved as it pulled away from the rock above it. The bowl is the floor the ice plucked out. The tarn, when there is one, is the puddle that filled the bowl after the ice melted.

Knowing how the building was built changes what you photograph in it. The headwall is most photogenic when struck by morning light, because it was carved by light's opposite — pressure and dark. The tarn is most photogenic at dusk, because the same minerals the glacier left in it are what give the water its impossible color.

I have photographed the same cirque north of Aspen four times. The fifth visit will be in the spring, when the bowl is half-full of new snow and half-full of the previous year's, and the two snows will not be the same color.