List of Slides for Crater Lake NP
- The early observers of this area described a mysterious
deep blue lake in Oregon.
- The lake actually occupies a caldera, formed
when a volcano called Mount Mazama exploded and collapsed, about 6845 years
ago.
- This display summarizes the phases of formation
of Crater Lake.
- The caldera gradually filled with water from
rain and snow.
- It contained no vegetation or animal life until
fish were introduced about 60 years ago.
- Wizard Island is a small cinder cone that
formed within the caldera, after the collapse.
- An andesite dike forms Backbone Ridge.
- Pyroclastic eruptions produced tuff, which was cemented together in
places where gas and steam passed through pipes. These areas were more
resistant to erosion and stand today as The Pinnacles.
- Layers of volcanic ash in soil can be traced
for miles. The brown layer is Mazama ash, the white is Mt. St. Helens ash
from an eruption around 3400 years ago.
- Evidence of glacial erosion, such as this U-shaped
valley, can be seen along the rim of Crater Lake, although no glaciers
remain in the park today.
- The caldera measures about 5 miles across.