Crater Lake NP, Southern Oregon

In our quest to pursue more evidence of volcanism we traveled to Crater Lake in southern Oregon on September 19th. This amazing natural feature preserves the remains of a large volcano (Mt. Mazama) which once stood over 12,000 feet. Geologists understand that mountain building began around 400,000 years ago with repeated lava flows and cinder cone development that formed a relatively broad (and not too steep) mountain. Intense temperature and pressure built up within the magma chamber underneath Mt. Mazama and led to a catastrophic eruption and subsequent collapse of the magma chamber around 7,700 years ago.

This eruption likely took place over several weeks, and the amount of ash spewed into the atmosphere was tremendous. It's estimated that 12 cubic miles of material was ejected into the atmosphere. This is enough material to cover the entire state of Oregon in 8 inches of ash! The eruption of Mt. Mazama is likely the largest volcanic event in North America for the last 500,000 years. Everything within a 30 mile radius would have been instantaneously obliterated by the power of this event.

After the magma chamber began to empty, fractures in the mountain formed in a ring and produced a very unique collapse event. Like a piston dropping in a cylinder, the mountain simply collapsed into the magma chamber. This is estimated to have been a short event on the order of 2-3 hours. Where once a 12,000 ft mountain stood, an enormous caldera was left. Over the next few thousand years snowmelt and rainwater filled in. It is exciting to contemplate the humans that would have witnessed this event. The local Klamath Indians include the eruption event in their own cosmology but it is hard to say exactly which Native American culture group would have been here so long in the past (8 millenia ago).

Crater Lake is a unique watershed with no river flowing in and none flowing out. The water is trapped and absolutely pristine.  Both the depth and the clarity of the water produce an electric blue color.  The picture below is unaltered.  Crater Lake is really that blue.  As sunlight passes into the water almost all wavelengths are absorbed except for the those from the blue spectra. These wavelengths bounce around the depths and ultimately reflect back out, entrancing viewers with its cobalt blue color.

 

For details on some of the features of this lake, see these tweets about the dimensions and the water clarity.

Because there is no river water flowing into the lake there are few living things in it.  Between the 1880's and 1940's several species of fish were introduced to create recreational opportunities for tourists. After that time conservationists recognized the natural lack of fauna present in the lake and sought to limit non-native species.  Today only two species of fish remain in the waters, rainbow trout and kokanee salmon.  People are allowed to fish in the lake, but they must use artificial bait to reduce the likelihood of contamination. The amount of water that fills the lake today is estimated to be 5 trillion gallons and it maintains this level because any surplus water seeps out through porous rock in certain spots around the caldera rim.



The island in the photo above is called Wizard Island due to its hat-like shape. This island is actually a newer cinder cone that erupted centuries after the described above. During the summer months the park maintains a boat service to bring tourists to the island. This was on our agenda but the tours stopped for the winter on September 15th. Julia was disappointed because she really wants to go on a boat ride, and we missed them in Glacier NP and now Crater Lake NP. Despite this, we still hiked the Cleetwood Trail down to the boat launch so we could touch the lake, conduct a new weather report, and test whether pumice floats.



In case you can't see it, it floats!

Crater Lake is also home to some overly friendly golden mantled ground squirrels. The absence of many predators combined with presence of many tourists means living is good for their kind. We assume that they receive plenty of handouts from hikers because one fellow was bold enough to climb right into our packs. These ground squirrels hibernate for the winter and put on a thick layer of fat in the fall. Perhaps this also helps explain their assertiveness.  In any case, this guy was almost in my lap more than once.