Newberry Volcano—Central Oregon’s sleeping giant

U.S. GEOLOGICAL SURVEY and the U.S. FOREST SERVICE—OUR VOLCANIC PUBLIC LANDS

Rising gradually southward to 4,000 feet above the City of Bend, Oregon, Newberry Volcano appears from Bend as a broad ridge on the horizon. Extending approximately 75 miles north to south and 27 miles east to west, the shield-shaped volcano and its extensive apron of lava flows cover almost 1,200 square miles, an area about the size of the State of Rhode Island, making it the largest volcano of the Cascades volcanic chain. This giant volcano is unlike a typical Cascade Range cone-shaped volcano (called a “stratocone”), such as South Sister to the west of Bend or Mount Rainier in Washington. Instead, Newberry is a “composite volcano” formed by diverse styles of eruption and has as many as 400 volcanic vents scattered across its slopes. Numerous lava flows drape its flanks, and some that were very fluid when erupted—like those typical of Hawaiian volcanoes—extend well beyond its base.

Very explosive eruptions, similar to that of Mount St. Helens in 1980, have occurred near Newberry’s summit and produced high plumes and flows of hot volcanic gases and ash (jagged tiny particles of rock and volcanic glass). A much bigger explosive eruption produced the large volcanic depression or “caldera” at the summit; its associated volcanic-ash deposits can be found as far away as the San Francisco Bay Area in California.

Volcanic activity at Newberry has created a unique and spectacular landscape, and in 1990 the Newberry National Volcanic Monument was established within Deschutes National Forest. Operated by the U.S. Forest Service, the monument encompasses all of the Newberry caldera, parts of the upper slopes of the volcano, and most of the volcano’s “Northwest Rift Zone.” Newberry caldera holds two beautiful lakes, Paulina Lake and East Lake, popular for fishing, boating, swimming, and camping.

How Did Newberry Grow to be the Largest Volcano in the Cascades?

Newberry Volcano lies east of the Cascades volcanic crest at the west margin of a broad volcanic region known as the High Lava Plains. The high-standing part of Newberry covers about 40 miles north-south by 25 miles east-west and encompasses nearly all of the volcano’s vents. However, Newberry’s lava flows extend much farther than this high part and to the north include the area of what is now downtown Bend, as well as the Redmond Municipal Airport. About 350,000 years ago, an early lava flow erupted from Newberry and flowed north until it reached Smith Rock, where it filled and moved down the channel of the Crooked River and also shifted the channel of the Deschutes River.

Growth of the broad Newberry shield began about 500,000 years ago. Newberry caldera was created about 65,000 years ago by a major explosive eruption and collapse event. This was the most recent of at least five caldera-forming eruptions that lofted pumice (frothy volcanic glass) high into the air and spread flows of extremely hot gases, ash, and pumice, called “pyroclastic flows,” across the volcano’s surface. Later lava flows have partly buried the deposits from this eruption, but one exposure can be seen at Paulina Creek Falls, where a deposit of pyroclastic flow and fall material was so hot that ash and pumice particles were welded together and then cooled into solidified rock.

Before formation of the caldera, Newberry’s summit was 500 to as much as 1,000 feet higher than present-day 7,984-foot Paulina Peak. Shortly after the most recent caldera-forming eruption, vents on the north side of Newberry fed large lava flows westward, which created and then flowed through Lava River Cave, diverting the Deschutes River. The lava flow that

Newberry Volcano Quick Facts

underlies downtown Bend is from that same eruption. Once the caldera was formed, more eruptions began to fill it with lava flows, and lava also erupted at numerous sites outside the caldera, covering much of the volcano’s north and south flanks. Between the end of the last Ice Age (about 12,000 years ago) when ice melted off the volcano and 7,700 years ago, Newberry Volcano erupted at least a dozen times.

Eruption that Formed Crater Lake Covers Newberry with Ash

About 7,700 years ago, a massive eruption caused the collapse of ancient “Mount Mazama,” forming a caldera that holds present-day Crater Lake, Oregon. Winds blew volcanic ash from that eruption northeast over Newberry Volcano, which is 75 miles away, covering much of it in a blanket of dusty ash and pumice as much as 6 feet thick on the volcano’s south flank. In Newberry caldera, the foundation of a Native American house was discovered underneath this ash layer, known as the Mazama ash, suggesting that the eruption disrupted an ancient human occupation. The ash sharply separates lava flows of Newberry’s older eruptions from lava flows produced by the volcano’s younger eruptions. The

Volcanic vents less than 12,000 years old

younger rocks attest to Newberry’s many geologically recent eruptions and are a warning that this “sleeping giant” could awaken again at any time.

The first eruptions after deposition of the Mazama ash came from a fissure that opened through the middle of Newberry caldera. The eruption

Ash, Pumice, and Lava Flow Hazards from Newberry Volcano

formed a ridge that divides East Lake from Paulina Lake. Along the fissure are the Interlake Obsidian Flow and Central Pumice Cone. The cone rises 700 feet above East Lake. It was built explosively when hot molten rock (magma) cooled and shattered after entering the lake water.

Cinder Cone and Lava Flow Northwest Rift Zone and Caldera Eruptions Form Frequently Visited Newberry Landmarks

Shortly after the eruptions that formed the Interlake Obsidian Flow and Central Pumice Cone, less explosive, more fluid lavas erupted

Pyroclastic Fall and Flow

from numerous cinder and spatter cones—conical hills formed of cooled blobs of ejected frothed lava. About 7,000 years ago, a 20-mile-long fissure system extending northwest from the caldera opened up, forming the Northwest Rift Zone. Numerous vents erupted, including 500-foot-high Lava Butte, which spawned a lava flow that temporarily dammed the Deschutes River. In places, fluid lavas surrounded and burned trees, leaving behind hollow molds, like those found along the trail at Lava Cast Forest.

The most recent eruption at Newberry, about 1,300 years ago, took place within the caldera. Explosive plumes of volcanic ash and pyroclastic flows were followed by slower lava flows of volcanic glass (obsidian) that created the spectacular Big Obsidian Flow. Not only did more than 10 feet of ash and fragments of volcanic rock fall inside the eastern caldera, but the ash can be found as far to the east as Idaho.

Both caldera lakes, Paulina Lake and East Lake, have hot springs with temperatures as high as 135° Fahrenheit. In 1981, temperatures higher than 500° Fahrenheit at a depth of 3,000 feet were found in a U.S. Geological Survey (USGS) drill hole sited in the center of the caldera. These

Why Monitor Newberry Volcano?

temperature measurements indicate that an active magma system lies beneath Newberry Volcano.

Research and Monitoring Reduce Risk in Future Eruptions

Because Newberry Volcano has erupted relatively recently (within the past 1,500 years) and more than 200,000 people live nearby, the USGS considers it a very high threat volcano. USGS scientists are studying Newberry’s geologic history to further understand the volcano’s past behavior and to make better assessments of future long-term volcanic hazards. Geologic research about a volcano’s past history allows scientists to make assessments of potential future hazards, thus enabling communities to make wise land-use planning decisions and to prepare emergency-response plans. Because volcanoes often have long periods of quiet that are punctuated by eruptive activity, scientists are also monitoring Newberry to detect any signs that this sleeping giant is reawakening. Seismometers that are installed on and around the volcano can measure earthquakes associated with the movement of magma and volcanic gas beneath the surface of Newberry, and Global Positioning System (GPS) instruments can detect and measure swelling of the volcano caused by magma accumulation underground.

Newberry Volcano is certain to erupt again. If signs of volcanic unrest at Newberry are detected, the USGS will issue advisories on the likely courses of events. The work of USGS scientists at Newberry is only part of the USGS Volcano Hazards Program’s ongoing efforts to protect people’s lives and property in all of the volcanic regions of the United States.

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