This earthcache was developed at the request of the staff of the Deschutes National Forest on the occasion of the 25th anniversary of the establishment of Newberry National Volcanic Monument. After orienting yourself and and visiting the Visitor Center (if open), drive east to the Big Obsidian Flow and hike to the highest viewpoint. This is one of the better and most easily reached viewpoints on the floor of Newberry Crater.
Given the following information:
A - N 43° 44.500 W 121° 14.135
B - N 43° 40.900 W 121° 14.205
C - N 43° 42.180 W 121° 13.620
To log this cache e-mail me the answers to the following 5 questions:
#1 - Coordinates at the highest viewpoint on the Big Obsidian Flow trail.
#2 - Use your GPS to determine the distance to Pt. A.
#3 - Use your GPS to determine the distance to Pt. B.
#4 - Use your GPS to determine the distance to Pt. C.
The recognized geographic name for the feature at the summit of Newberry Volcano is Newberry Crater.
Although the first use of caldera in geologic literature was in 1815, the term’s definition has evolved over time and the modern definition of a caldera dates to 1979 when Williams and McBirney redefined calderas as “large collapse depressions, more or less circular in form, the diameter of which is many times greater than any included vent.” A more general description of a caldera is that it is a large collapse feature and can be many miles in diameter while a crater is generally a constructional feature that is typically less than a mile in diameter.
Answer #2 plus #3 is the minimum diameter of Newberry Crater.
Answer #4 is the diameter of the largest exposed vent in Newberry Crater.
#5 - What do you think the summit feature of Newberry Volcano should be called?
Caldera collapse is associated with large-scale magma eruption. The eruption can be non-explosive and feed large volume lava flows or it can be explosive and erupt large volumes of pumice and ash. The caldera forming eruption often begins from a single vent and expands to a ring vent phase during which the caldera collapse occurs. Following caldera formation future eruptions can be scattered across the caldera or localized along structural trends. In smaller calderas later eruptions can fill the caldera and build a new summit.
The following description of Newberry Volcano and Newberry Caldera is based on ongoing research by the U.S. Geological Survey and is summarized in USGS Fact Sheet 2011-3145 “Newberry Volcano—Central Oregon’s Sleeping Giant.
The growth of Newberry Volcano began about 400,000 years ago. 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 (Paulina Peak Earthcache - GCQ0Z1). Newberry caldera was created about 75,000 years ago by a major explosive eruption and collapse event. This was the most recent of at least three caldera-forming eruptions that erupted 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 (Paulina Creek Falls Earthcache - GCQ36T), 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 (“tuff of Paulina Creek Falls”).
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 (Lava River Cave Earthcache - GCQ5FJ) , diverting the Deschutes River. The lava flow that underlies downtown Bend and the Redmond airport 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) and 7,700 years ago, Newberry Volcano erupted at least a dozen times.
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.
The first eruptions after deposition of the Mazama ash came from a fissure that opened through the middle of Newberry caldera. The eruption 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.
About 7,000 years ago, a 20-mile-long fissure system extending northwest from the caldera opened up, forming the Northwest Rift Zone from which fluid lavas erupted from numerous cinder and spatter cones. Numerous vents erupted, including 500-foot-high Lava Butte (Lava Butte Summit Earthcache - GCQ9GZ) and (Lava Butte Breach Earthcache - GCQ7YG), which spawned a lava flow that temporarily dammed the Deschutes River at Benham Falls (Benham Falls Earthcache - GCQ5FP) . In places, fluid lavas surrounded and burned trees, leaving behind hollow molds, like those found along the trail at Lava Cast Forest (Lava Cast Forest Earthcache - GCPW9X).
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 obsidian (volcanic glass) that created the spectacular Big Obsidian Flow (Big Obsidian Flow Earthcache - GCQ36N). 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 temperature measurements indicate that an active magma system lies beneath Newberry Volcano.