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Xu Jiandong and others of the Institute of Geology took part in field investigation to the Cascade volcanic area of USA

2015/12/29 10:19:02

The field investigation to the Cascade volcanic area of USA, organized by Prof. Shan de Silva of Oregon State University, was conducted from June 20 to 28, 2015. This area is one of the three largest active volcanic fields in the United States, which straddles the State of Washington, State of Oregon and State of California on the west coast of the United States. It is a part of Pacific Ring of Fire. The Pacific Plate dives eastwards below the North American plate with partial melting. The magma surges upwards along weak surfaces and erupts and forms the Cascade volcanic area. Its genesis bears resemblance with the China’s Changbaishan volcanic area and Japan’s island arc volcanoes, so this field study attracted the volcanic researchers of China and Japan. Researchers Xu Jiandong, Li Ni, Yu Hongmei and Assistant Zhao Bo of the Institute of Geology, CEA went to Portland, USA and attended the field study of the Cascade volcanic area at the invitation of Professor Shan de Silva (Figure 1).

Figure 1. Photos of the kickoff ceremony of the field study of Cascade volcanic area

1.       Field investigation of typical volcanoes

This field study has four typical objects:

(1).   Mount St. Helens: The most famous eruption of Mount St. Helens happened on May 18, 1980, which formed volcanic debris flow and airborne volcanic ash, claimed 57 lives and created destructive impact on the highways, railways, residences and other infrastructure facilities near the volcano. Later on, the volcanic mud-rock flow caused heavy economic loss to the cargo transport on the Columbia River. In this study, the discussed content includes the cone form of Mount St. Helens, the phase of the volcanic debris flow formed from the eruption in 1980, landform and other features (Figure 2-a).

(2).    Newberry Volcano: The Newberry volcano became active 600,000 years ago. In the crater, there are two crater lakes in the east and west, respectively and in the middle there is a parasite crater. The latest activity of the volcano was about 1300 years ago, which formed famous obsidian lava flow. The study group compared the pantellerite at Changbaishan Weather Station with the stratigraphic characteristics of the obsidian lava flow, and thought that they bear similarity in genesis (Figure 2-b) .

(3).    Crater lake: The Crater lake is a typical calderas. It was formed 7,700 years ago. The volcanoes in this region erupted along ring faults. As the inside of the magma chamber was hollow, the whole volcanic field collapsed and formed a crater lake. The volume of this eruption was 50km3, 100 times the eruption volume of Mount St. Helens. Volcanic debris flow and airborne volcanic ash were produced then. It is similar to the Chinese Changbaishan Tianchi Crater in morphology and geomorphic features of volcanic debris flow (Figure 2-c).

(4).      Lava butte Volcano: Lava butte Volcano belongs to Newberry Volcanic Field. Its eruption scale is much smaller than that of the latter. 7,000 years ago, basaltic explosive eruption and effusive eruption of Lava butte Volcano occurred, forming cinder-type lava flow and cinder cone. It is similar to the “flower-like lava” lava flow in Chinese Wudalianchi Volcanic Field. The study group and Prof. Shan de Silva of the organizer discussed its genesis and thought that they are both of “aa” lava (Figure 2-d);

Figure 2 Photos of typical volcanic deposit and landform taken during field study

a- Mount St. Helens; b-New berry Volcano; c-Crater Lake Calderas; d-Lava butte Volcano

2.       Volcano Monitoring Condition of “Cascade” Volcanic Field

Except the typical volcano field study routes, we also listened to the report of chief scientist John W. Ewert in “Cascade” Volcano Observation Station of USGS. He also showed us around the seismic data monitoring center, equipment production workshop and various kinds of volcano monitoring equipment in the volcano station (Figure 3).

After the visit, we felt that domestic equipment is not backward, but American scientific research personnel are superior to us in openness, innovation and the ability to redevelop original equipment. CVO independently researched and developed monitoring equipment, which integrates GPS, earthquake detection, view screen monitoring and other monitoring means (Figure 3-d). The equipment is deployed by helicopter. It is applicable to the volcanic areas where volcanic precursor activity is active and scientific research personnel are inaccessible.

Figure 3 Photos taken during visit to “Cascade” Volcano Station of USGS

a-group photo; b-volcanic earthquake data monitoring center; c- equipment production workshop; d-multifunction volcano monitoring equipment

Through this field study, we carried out extensive academic exchange with American and Japanese experts, showed our research findings on Changbaishan Volcano and compared them with Crater lake volcano and made clear of the direction of our future research focus. In the study, we also saw the shortfalls of China in volcano monitoring and research. For example, CVO does a solid job in disaster prevention and mitigation and particularly we have a large gap from them in real-time monitoring.