Last week, we saw Heaven Lake at Baekdu volcano in Asia.**
Now let’s look at Crater Lake, which fills a caldera that also formed in a VEI 7 eruption.
Per the Smithsonian’s Global Volcanism Program report on this volcano,
The spectacular 8 x 10 km Crater Lake caldera in the southern Cascades of Oregon formed about 6850 years ago as a result of the collapse of a complex of overlapping shield and stratovolcanoes known as Mount Mazama…The explosive eruptions triggering collapse of the 8-10 km wide caldera about 7500 years ago were among Earth’s largest known Holocene eruptions, distributing tephra as far away as Canada and producing pyroclastic flows that traveled 40 km from the volcano. A 5-km-wide ring fracture zone is thought to mark the original collapse diameter. The deep blue waters of North America’s second deepest lake, at 600 m, fill the caldera to within 150-600 m of its rim. Post-caldera eruptions within a few hundred years of caldera formation constructed a series of small lava domes on the caldera floor, including the partially subaerial Wizard Island cinder cone, and the completely submerged Merriam Cone. The latest eruptions produced a small rhyodacitic lava dome beneath the lake surface east of Wizard Island about 4200 years ago.
A natural lab
The volcano is still active and monitored closely. It also is a teacher, according to the USGS:
Excellent preservation and easy access make Mount Mazama, Crater Lake caldera, and the deposits formed by the climactic eruption constitute a natural laboratory for study of volcanic and magmatic processes. Research relating to the caldera-forming eruption has been of fundamental importance to volcanologists, helping them to understand large explosive eruptions, compositional zonation in magma chambers, and collapse caldera mechanisms. The climactic eruption is also the source of the widespread Mazama ash, a useful Holocene stratigraphic marker throughout the Pacific Northwest, adjacent Canada, and offshore.
Tourism and hazards
Crater Lake is such a popular tourist attraction, most of us tend not to think overmuch of the hazards there. Certainly those who live nearby are aware of them, though!
**Of note, many people live around and visit Changbaishan/Baekdu in North Korea and China, too, but contrast how little is known about that volcano compared to Crater Lake. Yet the hazards are similar – in fact, Baekdu’s “big one” happened much more recently. As well, it has had periods of restlessness in this century as well. This amateur thinks that might mean the Korean/Chinese volcano is the more dangerous of the two. In any event, so much more needs to be done there!