The Pumice Castle
Of the many colourful volcanic formations in the walls surrounding Crater Lake, The Pumice Castle, on the east wall, attracts the attention of many visitors viewing the crater walls from the rim, particularly when the afternoon sunlight emphasises the strong pattern of orange colour on the east wall.
The Castle is part of an extensive lenticular bed of fragmental pumice outcropping on the crater wall about 400m feet above the level of the lake, or 122m below the crater rim just south of Cloudcap Bay (on the left of the image).
The bed of pumice has a maximum thickness of 58m. Below it much of the section of the crater wall is hidden by talus, except for a few thin layers of lava and beds of fragmental material. Immediately above the lenticular bed of pumice is a thick, massive bed of andesite. Above the andesite occurs the pumice which mantles the remnants of Ancient Mount Mazama and the region extending for many miles beyond.
Although the Castle looks orange in the above image, there is in fact a much more sublte range of colours in it, including layers of brownish-red, light buff to pink, grey, black, and brown rocks, mainly pumice. It is the interspersing of harder, resistant materials such as andesite and obsidian amidst the layers of pumice that explains why erosion has produced the feature.
In addition to the scenic value of The Pumice Castle, it is a significant scientific feature in that it is evidence of a pumice eruption which occurred earlier than the ejection of material represented by the great thickness of pumice exposed at the top of the crater wall, and which mantles the region for miles beyond the crater rim.
On the far horizon in the left of the image can be seen Mount Thielsen. Some 2,800m tall, it is an extinct shield volcano that stopped erupting some 250,000 years ago. Glaciers have heavily eroded the volcano, creating precipitous slopes and the distinctive peak. The peak attracts lightning strikes and fulgurite (lightning-fused soils) can be found on its slopes.
The Pumice Castle
Of the many colourful volcanic formations in the walls surrounding Crater Lake, The Pumice Castle, on the east wall, attracts the attention of many visitors viewing the crater walls from the rim, particularly when the afternoon sunlight emphasises the strong pattern of orange colour on the east wall.
The Castle is part of an extensive lenticular bed of fragmental pumice outcropping on the crater wall about 400m feet above the level of the lake, or 122m below the crater rim just south of Cloudcap Bay (on the left of the image).
The bed of pumice has a maximum thickness of 58m. Below it much of the section of the crater wall is hidden by talus, except for a few thin layers of lava and beds of fragmental material. Immediately above the lenticular bed of pumice is a thick, massive bed of andesite. Above the andesite occurs the pumice which mantles the remnants of Ancient Mount Mazama and the region extending for many miles beyond.
Although the Castle looks orange in the above image, there is in fact a much more sublte range of colours in it, including layers of brownish-red, light buff to pink, grey, black, and brown rocks, mainly pumice. It is the interspersing of harder, resistant materials such as andesite and obsidian amidst the layers of pumice that explains why erosion has produced the feature.
In addition to the scenic value of The Pumice Castle, it is a significant scientific feature in that it is evidence of a pumice eruption which occurred earlier than the ejection of material represented by the great thickness of pumice exposed at the top of the crater wall, and which mantles the region for miles beyond the crater rim.
On the far horizon in the left of the image can be seen Mount Thielsen. Some 2,800m tall, it is an extinct shield volcano that stopped erupting some 250,000 years ago. Glaciers have heavily eroded the volcano, creating precipitous slopes and the distinctive peak. The peak attracts lightning strikes and fulgurite (lightning-fused soils) can be found on its slopes.