Wednesday, July 16, 2008

Former Mt. Mazama - Crater Lake, the Pinnacles

The history of the "pinnacles" below began about 7,700 years ago when the eruptions of Mt. Mazama were reaching their climax. Torrents of red-hot, gas-charged pumice poured down Mazama's slopes at speeds of up to 100 mph (160kph). On top of this came a flow of heavier rocks called scoria. These glowing avalanches flooded downslope for many miles, leaving deep deposits in their wake.

Temperatures in the deposits may have exceeded 750 F (400 C). Plumes of vapors appeared, as gasses escaped from the settling rocks through vents called fumaroles. Minerals in the gasses, combined with extreme heat, welded the sides of the fumaroles in the shape of slender cones. Since then, streams have eroded a canyon through the deposits, exposing the cones. Many of these fossil fumaroles are hollow.

The glowing avalanche deposits took years to cool. Hot gasses escaped through fumaroles whose shapes are preserved in the pinnacles.

Glowing avalnches from Mt. Mazama filled surrounding valleys with deposits of pumice and scoria. Today, streams are cutting new valleys.

Pinnacles Overlook
Located at the end of a 7 mile (11-km) spur road, the Pinnacles are well worth the detour from the Rim Drive. A colorful collection of 100 foot (30 Meter) spires are being eroded from the canyon wall. The spires are "fossil furmaroles", each marking a spot where volcanic gas rose up through hot ash deposits, cementing the ash into solid rock.

The Pinnacles Overlook is not visible from Rim Drive and the Pinnacles Overlook is easy to miss.

Another view of the Pinnacles at Crater Lake National Park.

Closer view of some of the Pinnacles.

The distinct layers of in the ash at the Pinnacles.

Just a small gust of wind and this happens.

We definitely would come back here , when John & Sarah are a bit older.

No comments: