Volcanic activity detected beneath Turtle Island (Gueishan Island, 龜山島) and the Datun Volcano Group (大屯山火山群) prove that they are active groups, Taiwan Volcano Observatory Director Lin Cheng-horng (林正洪), who is also an earth science researcher at Academia Sinica, said yesterday.
An active volcano is defined as having a magma reservoir or having erupted in the past 10,000 years, Lin said as he told a news conference about his team’s research over the past decade at the observatory on Datunshan (大屯山) in Taipei’s Yangmingshan National Park.
Almost no geologists in Taiwan thought the volcano group might be active about 15 years ago, as earlier studies had suggested its latest eruption might have occurred about 100,000 years ago, he said.
Photo: Lu Chun-wei, Taipei Times
However, his team has documented the existence of magma chambers beneath Datunshan through the variations in primary waves (P waves) and secondary waves (S waves) of earthquakes since the observatory was set up in 2011, he said.
S-waves cannot penetrate a magma reservoir, which also slows the transmission of P-waves — and both phenomena have been observed in the areas beneath Datunshan and Turtle Island, Lin said.
The island, which is about 10km off the coast of Yilan County, is only populated by military personnel, he said.
Volcanic eruptions under the island were more likely than under Datunshan and might trigger small-scale tsunamis off the coast of Yilan, he said.
However, there is no reason for the public to panic, because volcanic eruptions, unlike earthquakes, can be forecast by monitoring increases in the concentrations of carbon dioxide and sulfate ions, he said.
Lin’s team found that several magnitude 4 earthquakes in Taichung and in Hualien County in 2015 triggered regular “tremors” — or as Lin said, “heartbeats” — beneath Datunshan every 18 minutes for more than a day after each quake.
The team is likely to have been the first to have documented such “regular” quake activities, but its monitoring of such activity was later discontinued.
The team’s findings were published in Scientific Reports, the Journal of Volcanology Geothermal Research and other journals between 2016 and last year.
While there have not been any volcanic eruptions in Taiwan during its recorded history, identifying new evidence about earlier volcanic activities is still exciting, he said.
He expects to improve the volcanic surveys on Turtle Island, where there are fewer monitoring devices, he said.
Volcanologists from around Asia are to meet in Taiwan in October for the 4th field camp of the Asian Consortium of Volcanology, which has previously been held in Japan and Indonesia, he added.
Lin said he was originally interested in earthquakes, but switched to volcanology about 15 years ago after visiting Japanese volcanologists.
The workings of lava and gaseous substances of volcanoes was more attractive than the breaks or fault lines of seismology, he said.
ANOTHER EMERGES: The CWA yesterday said this year’s fourth storm of the typhoon season had formed in the South China Sea, but was not expected to affect Taiwan Tropical Storm Gaemi has intensified slightly as it heads toward Taiwan, where it is expected to affect the country in the coming days, the Central Weather Administration (CWA) said yesterday. As of 8am yesterday, the 120km-radius storm was 800km southeast of Oluanpi (鵝鑾鼻), Taiwan’s southernmost tip, moving at 9kph northwest, the agency said. A sea warning for Gaemi could be issued tonight at the earliest, it said, adding that the storm is projected to be closest to Taiwan on Wednesday or Thursday. Gaemi’s potential effect on Taiwan remains unclear, as that would depend on its direction, radius and intensity, forecasters said. Former Weather Forecast
As COVID-19 cases in Japan have been increasing for 10 consecutive weeks, people should get vaccinated before visiting the nation, the Centers for Disease Control (CDC) said. The centers reported 773 hospitalizations and 124 deaths related to COVID-19 in Taiwan last week. CDC Epidemic Intelligence Center Director Guo Hung-wei (郭宏偉) on Tuesday said the number of weekly COVID-19 cases reported in Japan has been increasing since mid-May and surpassed 55,000 cases from July 8 to July 14. The average number of COVID-19 patients at Japan’s healthcare facilities that week was also 1.39 times that of the week before and KP.3 is the dominant
The Chinese Communist Party’s (CCP) working group for Taiwan-related policies is likely to be upgraded to a committee-level body, a report commissioned by the Mainland Affairs Council (MAC) said. As Chinese President Xi Jinping (習近平) is increasingly likely to upgrade the CCP’s Central Leading Group for Taiwan Affairs, Taiwanese authorities should prepare by researching Xi and the CCP, the report said. At the third plenary session of the 20th Central Committee of the CCP, which ended on Thursday last week, the party set a target of 2029 for the completion of some tasks, meaning that Xi is likely preparing to
US-CHINA TRADE DISPUTE: Despite Beijing’s offer of preferential treatment, the lure of China has dimmed as Taiwanese and international investors move out Japan and the US have become the favored destinations for Taiwanese graduates as China’s attraction has waned over the years, the Ministry of Labor said. According to the ministry’s latest income and employment advisory published this month, 3,215 Taiwanese university graduates from the class of 2020 went to Japan, surpassing for the first time the 2,881 graduates who went to China. A total of 2,300 graduates from the class of 2021 went to the US, compared with the 2,262 who went to China, the document showed. The trend continued for the class of 2023, of whom 1,460 went to Japan, 1,334 went to