Mazuku

[1][3] Mazuku primarily occur on northern shores of Lake Kivu on both sides of the twin towns of Goma in the Democratic Republic of the Congo (DRC) and Gisenyi in Rwanda where local communities in these areas use this term in their vernacular (Kinyabwisha language) to describe the evil winds.

[15] It is divided into two main segments: the volcanically active Eastern branch, ~45Ma which passes through Djibouti, Eritrea, Kenya, and northeastern Tanzania, and the younger, seismically active Western branch, (~5 and 8Ma), that cuts through the Democratic Republic of the Congo (DRC), Uganda, Rwanda, Burundi, southwestern Tanzania, Zambia, Malawi, Zimbabwe and terminates at the Okavango Delta in Botswana.

[1][21][8] Isotopic signature from He and C gases analyses has confirmed that the origin of mazuku is mainly magmatic, as opposed to being derived from thermal decomposition of organic matter.

[2][3][12][22] These gases are temporarily trapped and stored in subsurface pockets, such as lava tubes formed during previous eruptions and remain isolated from the rest of the surrounding hydrothermal system.

[8][1] In the anoxic zones, methanogenic bacteria converts CO2 into CH4 through a process called methanogenesis, whereby over time, both CO2 and CH4 accumulate under extremely high pressure creating a potential future limnic eruption disaster.

[8][23][24] However, CH4 is currently extracted economically in Lake Kivu through degassing which reduces the risk of a dangerous limnic eruption while providing a valuable energy source for power generation.

[1][4] The bulk geochemical composition of the CO2-rich dry gases in mazuku consists of a mixture of variable proportions of other atmospheric components, such as N2, O2, and Ar, with smaller amounts of CH4, H2S and water vapour.

These gases accumulate in low-lying areas, valleys, or confined spaces or in the stratified water layers of meromictic lakes, creating hazardous conditions and deadly asphyxiation zones for humans, wildlife, and plants across different continents.

[1][36] The primary source of the gas was volcanic CO2 emissions, confirmed by C-isotope signatures, which had accumulated in the lake's stratified waters over time, leading to increased pressure.

[3][36] Seismic activity and an underwater landslide were responsible for the disturbance of the lake's stratification, releasing the trapped CO2 violently and causing a very dangerous gas outburst.

[23][8] The event was classified as a lake overturn which is a very rare phenomenon where dissolved volcanic gases are released from the stratified bottom layers of lakes after a mechanical disturbance[8] Mammoth Mountain, a dormant volcano in the Sierra Nevada region of California, United States, is underlain by a shallow dacitic dome that releases cold and dry CO2-rich gases (98v% CO2) through fumarolic vents and fractures located on the flanks of the mountain.

[40][41] These seismic events, combined with the mountain's bulging and exhumation, fracture the surface and allow high-pressure volatiles to escape, further contributing to the release of CO2 in the tree-kill zones.

Amiata is a dormant volcano located in Tuscany, Central Italy, and it is known for its significant emissions of dry and cold CO2-rich gases, which are primarily magmatic in origin.

[42] The gases originate from the deep geothermal system beneath the volcano and pass through a permeable network of faults and fractures by passive mechanism degassing processes.

In 1979 it experienced a tragic phreatic eruption disaster when a mixture of steam, lahar and toxic gases were released from the open cracks and fissures located near the crater and gushing down the valley asphyxiating insects, rodents, big animals like goats, dogs and cows as well as claiming lives of 172 people.

[36][23] If the concentration of CO2 is high enough and maintained in a prolonged outgassing event, even vegetation can be affected by the mazuku, as is the case on Mammoth Mountain in California, United States, where deforestation has occurred as well as CO2 poisonings, including the deaths of two skiers, one in 1995 and one in 1998.

Ngozi[20][48] Cava dei Selci[29] Gas blowouts, ground swells and roads collapses Azores The areas experiencing mazuku emissions are facing with multiple forms of hazards due to their proximity to active volcanoes.

[1] For instance, in regions near active volcanoes, such as the Virunga Volcanic Province, people, livestock, and wildlife in low-lying areas are silently killed by mazuku gases.

[23] However, if triggered by an external mechanical disturbance as volcanic activity, an earthquake, or landslide, a limnic eruption (also known as a lake overturn) could occur, releasing a cloud of these gases explosively.

[4] Mapping these areas through gas concentration and flux measurements can be of a great help during construction and settlement allocation decisions[7][29] Education and Sensitization campaigns: There should be continued scientific research on CO2 emissions in volcanic active regions that includes creation and improvement of existing CO2 dispersion models on the causes and occurrence of mazuku.