The West Thumb is an "appendage" of the enormous Yellowstone Lake within the park. Adjacent to the thumb is its namesake geyser basin. This is one of the first spots that you can witness the hydrothermal activity of Yellowstone Park if you've entered from the south. This particular feature isn't actually a geyser, but rather a fumerole that bubbles and steams but does not erupt like a geyser. Visually I was struck by the relationships between the foreground rocks, the reflections, and the cloud-filled blue sky: they appear to be all parts of the same whole, a continuum from earth to sky.