What is a mud volcano?

Mud volcano is a kind of "fake volcano" that looks like a volcanic eruption. The biggest difference between it and a volcano is that a volcano erupts magma, while a mud volcano erupts mud.

Mud volcanoes are mostly distributed on faults or anticline axes, and the exposed strata are mostly mud sandstone. When a large amount of underground fluid is subjected to huge pressure, the fluid carries mud and sand and gushes out from the weak zones of the crust such as faults, accumulating on the ground to form mud volcanoes.

The formation of a mud volcano requires three conditions: first, there must be head pressure of groundwater; second, there must be a fault or crack from the pressure point to the ground; and finally, there must be mudstone that can become slurry when it comes into contact with water.

▲Mud volcano erupting. Photo by George (Photo by Tuchong Creative)

01How much do you know about mud volcanoes around the world?

There are more than 2,000 mud volcanoes discovered on land and in shallow seas around the world, mainly distributed in the Alpine-Tethys suture zone and the Pacific Rim, and most of them are distributed in the South Caspian Basin. The Caspian Basin is the largest depression in the world, with many areas below sea level. It is also the lowest point in Europe, with the lowest point 28 meters below sea level. It is not only rich in oil, but also has more than 400 mud volcanoes, of which 220 are located on land and more than 170 are located in the ocean.

Famous mud volcanoes in the world include Yellowstone Park in the United States, Makran in Iran, Buza in Romania, etc. The Baku region of Azerbaijan is the place with the most mud volcanoes in the world, with about 220.

Mud volcanoes in my country are mainly distributed in Taiwan and Xinjiang. They are mainly small mud volcanoes. In addition, there are sporadic records of discoveries in the upper reaches of the Tata River on the edge of the Qaidam Basin in Qinghai, the Qujiang River area in the Sichuan Basin, and southern Jiangsu.

▲The crater of an active mud volcano. Photo by Tycson1Adobe Stock (Photo by Tuchong Creative)

02Taiwan Mud Volcano

64 mud volcanoes have been discovered on land, mainly distributed in Tainan, Kaohsiung, Pingtung and Taitung County in the southern part of Taiwan Province and the adjacent southwestern sea area. The regional tectonic position belongs to the Southwest Taiwan Basin.

Most mud volcanoes are distributed along the Gutingkeng anticline and the Qishan fault. Since many cracks are generated in the anticline axis and the fault, providing channels for the upwelling of materials, the main driving force of mud volcano eruptions is the abnormally high pore pressure. Earthquake activities, precipitation, etc. can cause a temporary increase in the pore pressure of the formation, thus causing the mud volcano to erupt.

▲Taiwan's Wudingshan mud volcano. Image from the Internet

03Xinjiang Mud Volcano

They are mainly located at the northern foot of the Tianshan Mountains, with the most representative being Nan Horgos, Dushanzi, Wusu City, Aktomuji and other places in Shawan County, each with several to dozens of eruption outlets. Among them, Baiyanggou Town in Wusu is home to the largest mud volcano group in Asia, and Sailiketi Ranch has the largest mud volcano pile in Asia. These mud volcanoes are all located in the Urumqi piedmont depression zone at the northern foot of the Tianshan Mountains, and are all located at the axis of the anticline fold. Obviously, their formation is also closely related to the structure here.

Dushanzi Mud Volcano

Huangtu Mountain, located 1 km southwest of the Dushanzi mining area of ​​the Xinjiang Petroleum Administration Bureau, once had 5 mud volcano vents, but now only 2 remain. One vent is a mud hole with strong activity, intermittently spraying mud. The mud is viscous, gray-green in color, and slightly smells of oil. The overflowing mud forms a mud volcano pile on the ground. The base diameter is about 10 meters, and the overflowing mud flows about 6.5 meters. The other mud volcano crater is pit-shaped, 1.1 meters deep, with thinner mud, more liquid in the upper layer, and oil spots on the surface. The smell of oil can be smelled at close range, but there is no obvious activity, and the bubbling interval is long.

▲Dushanzi mud volcano. Photo/Zhang Bo-Spinach Garden (TuChong Creative)

Khorgos Mud Volcano

Located in Jingou River, South Horgos, Shawan County, Xinjiang. Structurally located in the axis of the Horgos anticline, there are two mud craters exposed. One was renovated in 1990 and uses a Hongqi-1 water level meter for continuous liquid level observation. The other vent is about 1 meter in diameter, with weak activity, bubbling, but no mud overflowing. Green and reddish-brown oil flowers float on the liquid surface, the smell is strong, and the mud is thin.

Wusu Ni Volcano Group

Located about 40 kilometers south of Wusu City, Xinjiang, it is distributed in the hilly area on the northern slope of Tianshan Mountain. The strata are mainly Jurassic red, purple-red mudstone and sandy mudstone. Within a range of about 200 meters long and 100 meters wide, there are currently more than 40 mud craters erupting. The largest diameter of the mud crater here is 4 meters, and the smallest is only the size of a broad bean. Most of the craters are round, and a few are oval or pear-shaped. The colors of the ejected mud are mainly blue-gray and reddish-brown. There are also dark brown oily substances floating on the surface of the mud. The violent eruption craters erupt more than 60 times per minute. The Wusu mud volcano group is subdivided into five types according to different shapes and sizes: mud cones, mud shields, mud pools, mud basins, and mud caves.

▲Wusun mud volcano. Photo/from the Internet

Aiqigou Mud Volcanoes

Located in the western branch of Aiqigou in Wusu City, there are two mud cones distributed on the Aiqigou fault zone, covering an area of ​​3,200 square meters. It is the largest mud volcano in mainland my country and a rare conjoined "twin" mud volcano in the world.

Baiyanggou Mud Volcano

Located in the north of the Sikeshu Coal Mine in Wusu City and on the east bank of Baiyanggou, the distribution area is 1.8 kilometers long from east to west and 1.2 kilometers wide from north to south. There are 53 mud volcanoes of different sizes, mainly including mud pools, mud basins, mud caves and mud shields. It is the most densely distributed mud volcano group in my country.

▲The “twin” cones of the Aiqigou mud volcano.

Aktomuji Mud Volcano

"Muji" means "mud, sand and stones ejected from the volcano" in Kyrgyz.

Muji Township mud volcanoes are mainly distributed in the river valley of Muji Township, Akto County, in a linear distribution, concentrated within a range of 7 kilometers. The overall direction is 120°-300°, and more than 40 mud volcanoes of different sizes can be seen, mainly in cone and basin shapes. Some mud volcano pits have dried up, and the largest one has a diameter of about 56 meters. A lot of water plants have grown on the edge of the crater, and a lot of water is stored in the middle. The smallest one has a diameter of about 15 cm and bubbles come out from time to time.

However, some experts believe that they are not mud volcanoes, but a unique type of spring mound.

▲Muji Mud Volcano. Photographed by 4pm (Photo by Tuchong Creative)

04Mud volcanoes and earthquakes

As a unique natural landscape, mud volcanoes are not only ornamental, but also have great research value due to their close connection with tectonic activities and oil and gas generation belts.

Earthquakes and mud volcanoes are both significant signs of modern crustal movement, and the eruption of mud volcanoes is strongly correlated with earthquakes. For example, on October 5, 1948, a magnitude 7.3 earthquake occurred in Ashgabat, the capital of the Republic of Turkmenistan, which caused the re-activation of mud volcanoes in the epicenter. In 2004, a magnitude 6.2 earthquake occurred in Taiwan, China, and mud volcanoes in Kaohsiung County erupted several times before the earthquake. The mud volcano distribution zone in the northern Tianshan Mountains is also an area where medium and strong earthquakes frequently occur. Some scholars have shown that the mud volcanic activity in this area is closely corresponding to the strong earthquake activity in the Tianshan Mountains, especially before and after some earthquakes of magnitude 5.0 or above in the northern Tianshan Mountains, which are sometimes accompanied by mud volcanic eruptions.

▲The mud volcano Gobustan near Baku, Azerbaijan at sunset. Photo by Alex Green (TuChong Creative)