Indeed it is. It is a caldera.
Yup... it is the remnant of Mount Mazama which blew itself to pieces in a pyroclastic event (think Mt. St. Helens times 1,000) about 20,000 years ago.
This just proves that we really are not positive about the meteoric origin of the extra-terrestrial craters. We have yet to see a crater formed by such means. We may see one tomorrow... or we may never be looking at the right time to see one being formed.