China not only has the "Black Myth Monkey King", but also the "Millennium Floating Turtle"!

There is an ancient myth that the Monkey King was born from the crack of the immortal stone in the Flower and Fruit Mountain, which is talked about by people all over the world. Little do people know that in the real world, there is a "thousand-year-old floating turtle" suspended in the sea on Taiwan, my country's treasure island. This "turtle" is actually a volcanic island with a unique shape. There are two round peaks on the island. The small peak on the east looks like a turtle head, the large peak in the middle looks like a turtle shell, and the strip of stone beach on the west looks like a turtle tail. People call it "Turtle Mountain Island". People from all over the world come here to admire this island miracle created by the magic of nature.

Guishan Island Volcano is a Holocene composite active volcano, geographically located about 12 kilometers east of Yilan County, Taiwan Province, China. Its tectonic position is at the junction of the Taiwan Fault System formed by the fracture and subsidence of the continental crust caused by the subduction of the Philippine Sea Plate to the Eurasian Plate, and the extension of the southern rift system of the Okinawa Trough. It has typical characteristics of the Western Pacific-arc-basin system.

Location map of Guishan Island volcano and surrounding structures (left, original map); aerial view of Guishan Island volcano (right, original map)

The Guishan Island volcano has not experienced a large-scale eruption in modern times. Scientists have discovered baked quartz sandstone in the breccia of the Guishan Island volcano. After thermoluminescence dating, it was found that the eruption time was about 7,000 years ago, and it belongs to a volcano that has erupted in the Holocene. In addition, above the accumulation layer of luminescence dating, there is also an accumulation layer of lava flow, which shows that the Guishan Island volcano still has overflow eruption activities after the eruption in 7,000 years, and sulfur jets and hot spring activities in the volcanic area are also relatively active. The Guishan Island volcano had a sulfur smoke (sulfur smoke) eruption 67 years ago, and smaller-scale eruptions continued in the following decades. In October-November 2021, the Guishan Island volcano experienced a large-scale sulfur smoke eruption, which erupted about 230 meters above sea level when the eruption was strong.

Existing volcanic and seismic observation and research data show that sulfur fumaroles and hot springs are relatively developed in the Guishan Island volcano and the surrounding sea areas. According to statistics, there are more than 30 hydrothermal fountains distributed in a water depth range of about 10-30 meters. The temperature of the hydrothermal fluids ejected from these hydrothermal fountains is as high as 116°C, the pH value (25°C) is as low as 1.52, and the flow rate is as high as 158 tons/hour. The main components of the ejected gas are H2O, followed by H2S, SO2, HCl, CH4, N2, etc. The sources of these gas components are diverse, mainly from the mantle, ocean lithosphere and seabed sediments. Volcanic hydrothermal fluids are ejected from these vents, forming sulfur-rich hydrothermal dispersion zones in the seawater. These dispersed hydrothermal fluids extend a long distance in the ocean, and the hot spring vents on the island will continue to release volcanic gases, which, combined with the geothermal anomalies in the volcanic area and the regional tropical marine climate, form strange clouds. This also explains the strange phenomenon of the "divine turtle" spitting smoke and wearing a hat on Guishan Island, which is mainly caused by local climate anomalies caused by thermal anomalies in the volcanic area.

Strange clouds appearing above the Guishan Island volcano (left picture, sourced from the Internet); the submarine hydrothermal diffusion area around Guishan Island (right picture, sourced from the Internet)

The "head" of Guishan Island is a volcanic cone left over from a volcanic eruption. Sulfur gas is still erupting today. The gas formed by the sulfur gas does not dissipate until mid-air. From a distance, the "head" looks like it is smoking. The "tail" of Guishan Island is a strip of gravel beach composed of andesitic volcanic rocks and gravel, which extends for more than 1,000 meters and is 3 meters high. Looking at Guishan Island in the sea from Yilan County, it is as if you can see the "turtle head" smoking and the "turtle tail" swinging left and right. The broken rocks around the island float and sink, just like the turtle claws swimming. Therefore, the locals also call it "Turtle Island that spits smoke and swings its tail."

"Turtle Island with smoke and tail" (Photo from the Internet)

In Yilan County, Taiwan Province, my country, you can see the Guishan Island volcano wherever there are no hills blocking it. It is well-deserved to be one of the most eye-catching landmarks in Taiwan Province. Guishan Island has always been famous for the eight wonders of Guishan. As early as the Qing Dynasty, "Guishan Rising Sun" was listed as the first of the eight scenic spots in Lanyang. The scenery on the island is most distinctive with the eight wonders of "Guishan Rising Sun", "Guishan Smoke", "Guishan Rock Cliff", "Guishan Egg Viewing Wonder", "Divine Turtle Wagging Tail", "Divine Turtle Wearing Hat", "Spectacle Cave Stalactite Wonder" and "Undersea Hot Springs Flowing Upstream". Except for "Guishan Rising Sun" and "Divine Turtle Wearing Hat" which are meteorological landscapes, the remaining six scenes are special volcanic landscapes formed by volcanic action and wave erosion.

The most interesting of the Eight Wonders is the "Turtle Egg Viewing". There is a small group of rock islands in the southwest of Guishan Island, quite close to the tail of Guishan Island. They are called Turtle Egg Island because they look like turtle eggs. There are some large rocks in the sea water around Turtle Egg Island that are not exposed to the water, which look like eggs laid by a giant turtle. In the past, two small islands could be vaguely seen on the southwest side of Guishan Island at low tide. Unfortunately, one night in 1943, the turtle eggs disappeared after a loud bang. Local residents speculated that they were hit by a mine. Now this landscape no longer exists, leaving only the story of "Turtle Egg Viewing".

In addition to these unique volcanic geological landscapes, the Guishan Island volcano has also developed two very distinctive tourist resources: one is the "401 Highland". The highest point of Guishan Island is 398 meters above sea level, plus the 3-meter-high two-story observation deck, the total height is 401 meters. It is called "401 Highland" by the locals. It is the second highest mountain in Taiwan's outlying islands, second only to Lanyu. The second is the "whale watching holy land". The waters near Guishan Island are one of the three major fishing grounds in Taiwan Province. March to September is the whale watching season on Guishan Island. During this season, on the way to the island by boat, there is a high probability of seeing dozens of whales and dolphins in groups, jumping and playing on the sea.

"401 Highland" of Guishan Island (left picture, sourced from the Internet); dolphins swimming in groups in the waters of Guishan Island (right picture, sourced from the Internet)

There are steep cliffs, hot springs, mountains, sea caves, lakes, special cliff plants and rich marine ecology on Guishan Island. Visitors can enjoy the different landscape changes of Guishan Island in different locations, climates and tidal conditions, which is also the charming charm of Guishan Island. Guishan Island has special geological conditions, and weathering and collapse of rocks on the island have been common in recent years. On July 23, 2019, the turtle head rock collapsed, and the falling rocks rolled down from the height of the turtle head, raising bursts of dust. The most recent collapse occurred on April 3, 2024. Due to a magnitude 7.3 earthquake in the waters of Hualien County, Taiwan, a small part of the rocks on the turtle head of Guishan Island, about 117 kilometers away from the epicenter, collapsed, and a large amount of dust was splashed from the bottom of the mountain, but the shape of Guishan Island did not change significantly.

The epicenter of the 7.3-magnitude earthquake in Hualien County, Taiwan, has a similar geological structure to the location of the Guishan Island volcano, and the two are relatively close. Existing seismic activity and geochemical monitoring data in the volcanic area show that the Guishan Island volcano has not yet shown obvious abnormalities, and the possibility of an earthquake triggering an eruption of the Guishan Island volcano is low.

This issue of science popularization ends! Friends, see you next time!

References in this issue:

[1] Song Yujia, Pan Xiaodong, Gu Guohui, et al. Analysis of the possibility of a magnitude 7.3 earthquake in the waters of Hualien County, Taiwan and its triggering of volcanic activity[J]. Advances in Earthquake Science, 2024, 54(4): 292-298.

[2] Chen Yugao, Wu Wenxiong, Liu Conggui, et al. Thermoluminescence dating of Guishan Island[J]. Nuclear Technology, 1999, 22(10): 633-634.

[3] Chen Xuegang, Qiu Zhongyan, Duan Wei, et al. Element enrichment characteristics of microscopic inclusions in hydrothermal natural sulfur in Guishan Island, Taiwan, China [J]. Earth Science, 2018, 43(5): 1549-1561.

[4] Lu Donghua. Research on shallow seismicity model in Taiwan[D]. Institute of Geophysics, China Earthquake Administration, Master's thesis, 2023.

[5] Zhang Haiyan. Hydrothermal gas composition and element diffusion distribution in Guishan Island and Green Island, Taiwan[D]. Zhejiang University, Master's thesis, 2013.

[6] Li Haiyan, Shao Zhigang, Ma Hongsheng, et al. Analysis of the movement characteristics of the Huadong Longitudinal Valley Fault in eastern Taiwan, China based on deformation observation [J]. Earth Science Frontiers, 2018, 1: 240-251.

Author of this issue: Song Yujia, Assistant Engineer, Institute of Volcanology, China Earthquake Administration, Jilin Province Earthquake Bureau

Gu Guohui, Engineer, Institute of Volcanology, China Earthquake Administration, Jilin Province Earthquake Bureau

Xu Zhitao, Institute of Volcanology, China Earthquake Administration, Jilin Province Earthquake Bureau, PhD

Sun Liying, Assistant Engineer, Jilin Earthquake Station, Jilin Province Earthquake Bureau

Ren Fangyu, Jilin Earthquake Station, Jilin Province Earthquake Bureau, Assistant Engineer

Ye Xiqing, Engineer, Institute of Volcanology, China Earthquake Administration, Jilin Province Earthquake Administration

Sveva·R·M PhD, University of Florence, Vesuvius Observatory, Naples, Italy

Li Haiyan, PhD, Fujian Seismological Bureau

Zhang Xin Guangdong Provincial Earthquake Administration PhD, University of Science and Technology of China

Li Mengmeng, Engineer of the Institute of Volcanology, China Earthquake Administration, Jilin Province Earthquake Bureau

Nikos S. Researcher, Institute of Geophysics and Volcanology, Rome, Italy; Feng Jingqiao, Senior Engineer, Jilin Earthquake Disaster Risk Prevention and Control Center, Jilin Province Earthquake Administration

Ma Fei, Engineer of Jilin Province Earthquake Disaster Risk Prevention and Control Center, Jilin Province Earthquake Bureau

Yan Hengqi, Jilin Earthquake Station, Jilin Province Earthquake Bureau, Assistant Engineer

Stefano C. Senior Researcher, Vesuvius Observatory, Naples, Italy

Guan Sheng, Engineer, Institute of Volcanology, China Earthquake Administration, Jilin Province Earthquake Bureau

Xu Zhikai, Postdoctoral Fellow, Institute of Oceanology, Chinese Academy of Sciences

Francesco L Senior Engineer, Vesuvius Observatory, Naples, Italy

Disclaimer: All pictures and texts in this article are for public benefit and do not have any commercial value.