| Newberry Volcano |
Article Index for Newberry |
Shopping Newberry |
Website Links For Newberry |
Information AboutNewberry Volcano |
Newberry Volcano 7,985 ft (2,434 m) high is a large Shield Volcano located 40 miles (60 km) east of the Cascade Volcanic Belt , the Cascade Range and about 20 miles (30 km) southeast of Bend, Oregon . It is not a typical shield volcano in that, in addition to erupting Basalt ic lavas, it also has erupted Andesitic and even Rhyolitic lava. The Volcano is 20 miles (30 km) in diameter, has an approximate volume of 80 mile³ (330 km³), and it possesses a large oval-shaped Caldera four by five miles in diameter, called the Newberry Caldera . Within the caldera there are two Lake s (Paulina Lake and East Lake) many Pyroclastic Cone s, Lava Flow s, and Obsidian domes. A deep gash in the northern caldera wall, dubbed The Fissure, is the end of a 29 mile (47 km) long series of fractures called the Northwest Rift Zone . Approximately 6,100 years ago, fissure basalt flows erupted from the rift and covered part of Newberry's northwest flank. GEOLOGY A great deal of volcanic activity has occurred on Newberry's shield, which itself has one of the largest collections of cinder cones, domes, lava flows, and fissures in the world (local residents call these parasitic vents the "Paulina Mountains", thinking of them as a separate Mountain Range ). Most of the cinder cones are 200 to 400 ft (60 to 120 m) high and have shallow saucer-shaped summit craters. They are typically surrounded by basalt or andesite that erupted from their bases, forming large Lava Bed s. On the northwest flank of the volcano, Lava Butte , located next to Highway 97 south of Bend, is a good example of this kind of cinder cone and lava bed. There are also about 20 rhyolite domes or fissures on the eastern, southern, and western flanks. Larger examples include McKay Butte on the west flank (580,000 years old), China Hat (780,000 years old) and East Butte (850,000 years old) on the far eastern base. During the late Pleistocene and Holocene there have been six eruptive episodes; four Rhyolitic (east half of the caldera) and two Basaltic (on the flanks).
Newberry's highest point is located 1,500 ft (450 m) above the southern caldera floor on Paulina Peak, which is just one peak on the caldera rim. The volcano's south flank descends into the basaltic flatlands of central Oregon. During the Apollo Program , parts of the volcano that resemble the Moon 's surface were used to train Astronaut s. CALDERA Newberry Caldera has existed possibly as long as 500,000 years, when the cone of the volcano is thought to have first collapsed. Subsequent caldera-forming collapse events have further deepened the caldera, but volcanic material and lakebed Sediment s have largely filled in much of this depth. Within the caldera there are two Lake s (Paulina Lake and East Lake), many Cinder Cone s, Lava flows, and Obsidian domes. The land area of the caldera is heavily Forest ed except in areas where there are more recent volcanic flows and features. Paulina Lake is drained by Paulina Creek, which passes through a narrow gorge through the western part of the caldera rim. East Lake does not have a known outlet and is thus 40 feet (13 m) higher than Paulina Lake. 6700 year-old Basalt flows separate the two caldera lakes. Rising 700 feet (230 m) above this flow is the Central Pumice Cone. Both lakes have Hot Spring s and drilling in 1981 found that temperatures in the caldera reach 280 ° C (510 degrees Fahrenheit ) at 3057 feet (941 m) below the caldera floor. This is the highest temperature ever recorded at a dormant Cascade volcano (higher than even The Geysers of California, the world's largest producer of Geothermal Power ). Newberry has had a caldera for possibly as long as 500,000 years, when a large Plinian Eruption (on the VEI scale) sent so much Pyroclastic material gushing from its vent that the then emptied Magma Chamber collapsed. This was repeated for several eruptions; each forming a slightly smaller caldera. The half-million year old (estimated) Teepee Draw tuff covers much of the volcano's shield and was from an eruption with an estimated volume of 10 cubic miles (42 km&2). This is thought to be the first in a series of caldera-forming eruptions that issued from Newberry's main vent system. One of the later layers is cut by Newberry's only stream, Paulina Creek. Subsidence of the caldera through time has been partly offset by the deposition of Tephra , lava flows, and lake sediment. The USGS has drilled 950 meters (3000 ft) below the present surface of the caldera and has found that:
There are several large flows of obsidian in the caldera, one of which, Big Obsidian Flow, was created around 1400 years ago and is thus the most recent caldera eruption. This particular flow erupted from a vent or fissure near the southern wall of the caldera and partially engulfed the Lost Lake pumice ring. SEE ALSO REFERENCES
EXTERNAL LINKS |
|
|