Located just inside the South San Juan Wilderness near Pagosa Springs, Opal Lake is one of the shortest hiking destinations.  It's one of the quickest ways to experience a mature aspen stand, and a scenic mountain meadow surrounded by dramatic volcanic cliffs.  It's also a great place to take young kids or friends from out of town who want a short, scenic hike. The lake itself is small, shallow, and murky (keep reading to the end to find out why), but the setting is gorgeous.      

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Although the trail is short, it climbs steeply during the first 3/4 of a mile.  At 0.5 mile, you'll cross a small stream.  Then you'll climb steeply to the scenic aspen forest, at which point the grade of the trail mellows for the rest of the hike.  You'll exit aspens and enter meadow lined with corn lily and views of the surrounding cliffs.  At mile 1, you'll cross White Creek and climb the rest of the way to the lake, but just before you get there, there is one last stream crossing.   

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Initially, you may be unimpressed by the lake because unlike most lakes in the area, Opal Lake was not formed by glaciers.  My theory is that it's just a giant beaver pond (the beaver dam can be seen in the lake's outlet) although I haven't seen any beaver activity since 1999.  Like all lakes, it has a limited lifespan.  Over time, lakes fill in with sediment and transition to wetlands, and eventually meadows.  Opal Lake is shallow and is transitioning to a wetland.  

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Opal Lake sits at the base of the Chalk Mountains, is fed by White Creek, and is a tributary (as well as the neighboring Leche Creek) to the Blanco River.  The white theme can be attributed to a fine white layer of volcanic ash that is embedded in the surrounding Chalk Mountains.  The violent, Mt. Vesuvius-style eruptions that shaped this area blasted pulverized rock into the air, which later settled and accumulated into layers.  When this ash layer is eroded by running water, the material is so fine that it doesn't settle very fast.  As a result, the streams in the area run slightly cloudy even at low flow. 

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More impressive than the lake is the spring that feeds it, which emerges from the ground about 100 yards upstream of the inlet.  If you inspect the streambed where the spring emerges, you'll find it's made up of the white volcanic ash, which has turned into clay (and the presence of the layer may be why the spring emerges where it does).  The spring immediately splits, half of the flow goes to the lake and the other half bypasses the lake, and becomes the stream that you have to cross right before you reach the lake.  A little bit of this white clay is eroded as the spring water contacts it, which gives the streams the cloudy appearance.

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I wouldn't recommend hiking around the lake perimeter because the north side is extremely brushy, but there's a unique vantage point of Squaretop from the south shore.