HAYLI GUBBI ERUPTS
On November 23, 2025 a surprisingly violent eruption of the volcano Hayli Gubbi brought world attention to this volcano and the seminal earth processes that caused its eruption in the geologically active Afar Triangle in Ethiopia.
Ethiopia is a modest sized landlocked nation in Eastern Africa with an exceptionally diverse terrane and of enormous geologic interest and importance. The Afar Triangle region of Africa is the site of a “hot spot” where the Earth’s crust is splitting apart to form new isolated continental masses as well as new ocean basins! This process, known as—Plate Tectonics—describes the active rupturing of continents, their movement or “drift” over the Earth’s surface, their convergence to form mountains and their submergence and subduction into the mantle at points of convergence. Plate Tectonics is a theory of extraordinary significance in the understanding of our dynamic Earth, its history and its life forms. Plate Tectonics explains why the Himalayas are so high, the Marianna Ocean Trench so deep, why Japan has so many earthquakes, why world-wide glaciers formed in the Pleistocene Ice Age more than a million years ago, why Elephants are found both in Africa and India and why marsupials are the dominant mammals in Australia.
Ethiopia’s Afar Triangle and Hayli Gubbi are part of an outdoor Plate Tectonics laboratory where scientists can study how and why continents fracture and move over the Earth’s surface.
The geological process at the Afar Triangle is initiated by rising hot (1000C -1200C) plumes of molten magma toward the surface. As it reaches the base of the crust the dense, hot, rising plume “domes up” (pushes up) and thins the Earth’s crust above it. Τhis now thin, domed -up crust is subject to fracture and separation. Highlands such as the Ethiopian plateau may form on either side of the fracture zone as a result of uplift. At the fracture zone, lateral movements (perhaps by convective flow in the mantle or gravitational drag of the uplifted crust plate itself). However it occurs, widening the fracture takes place and initiates the ultimate splitting off of masses of continental bodies and the formation of ocean basins in the new depressed zone between continental masses.
Thus it is in Ethiopia’s Afar Triangle that we can observe and study this process of Plate Tectonics which occurs worldwide. See note on Pangaea below.*
Hayli Gubbi is located in an isolated, difficult to , area of north-eastern Ethiopia. Most reports emphasize the fact that Hayli has been dormant for more than 12,000 years.What was unusual was the explosive and violent eruption of this seemingly inconsequential, shield cone volcano located in a poorly known part of the world.
ASH CLOUDS
The violence of the Hayli Gubbi eruption was remarkable and the height of the gas and ash cloud generated towered up to 45,000 feet, an elevation well into the stratosphere and at heights where commercial passenger aircraft regularly cruise. This incursion into areas which affect safety of international travel caused consternation in transportation management and air travelers around the world. Planetary winds caused ash clouds generated by Gubbi to drift across the Arabian peninsula and over Pakistan and India, causing flight cancellations and disruptions in those nations.
ETHIOPIA—AN OUT DOOR GOLOGY LABORATORY
Let’s start with Ethiopia. This ancient nation known as “the Land of Cush” in the Old Testament, is a modern landlocked country in east Africa and about twice the size of France. If one begins in Egypt’s Nile River and continued upstream (south) passing through the nation of Sudan would reach Ethiopia. The high plateaus of Ethiopia are the source of a major branch (the Blue Nile) of headwaters of the Nile River. Geographically Ethiopia lies across the Red Sea from Saudi Arabia and occupies a major part of the inland area of what is known as the Horn of Africa, a promontory which thrusts` out into the Indian Ocean. To the south of Ethiopia and occupying the Indian Ocean shoreline is the nation of Somalia (and it neighbor further southwest is Kenya); while to the northeast, the nation of Eritrea, hugs the shore of the Red Sea. To the east, blocking Ethiopia from access to the Red Sea is the tiny state of Djibouti (about the size of the Italian island of Sardinia).
THE AFAR HOTSPOT
Hotspots at the Earth surface form when exceptionally hot plumes of hot magma rise up from the mantle and melt their way into the crust. Ethiopia is the site of one of the three largest hot spot plumes in the Northern Hemisphere: the Hawaii Hot spot, Yellowstone Hotspot, the Canary Islands Hot Spot, Iceland and the Afar Hotspot in Ethiopia. The Afar Hotspot is perhaps the largest.
Three crustal plates, the African Plate, Somali Plate and the Arabian Plate are pulling apart to form the “triple point” which is centered at the Afar hot spot. Ethiopia is the site of one of the planet’s largest and most active hot spots (Afar Hotspot) where hot plumes of magma rise up toward the surface forcing the Ethiopian crust upward as much as 5,000 feet to produce a highlands called the Ethiopian Plateau. This central highland of diverse flora and fauna in Ethiopia is cut across by a long, wide depression (the Great Rift Valley (GRV) and the o. These rifts or splits in the Earth crust are moving apart as a result of the upwelling of hot maga and its movement.
The GRV and Danakil Depression form one leg of a triple point where three crustal rifts intersect. The intersection point occurs just off the coast of the tiny nation of Djibouti, at the Bab el Mandeb Strait -the narrowest point in the Red Sea.
The Red Sea rift and the Gulf of Aden rift form two legs of the triple point, while the less apparent, younger, but just as active leg is formed by the Great Rift Valley and Dankil Depression in Ethiopia (and its neighbors). (See Google Maps or Google Earth to visualize this more clearly.)
The GRV is a more recent crustal fracture, or split in the Earth crust or rift which is moving to separate the Somali Plate from Africa (we assume Africa is stable). Nearby, the Arabian Plate is separating from the latter two plates as the Red Sea rift grows wider. (Take a look at Google Maps or Google Earth in this region to actually see the rift in the Red Sea sea-bed itself.)
The entire rift system in Ethiopia is affected by “geothermal features” such as large shield cone volcanos like Erta Ali, thermal or hot-springs, hot mud lakes, and rift zones with depressed regions such as the Dankeli Depression and the Great Rift Valley, as well as the Ethiopian Highlands which are the result of doming of sub crustal upwelling which have pushed up the Earth crust and caused thinning as well. The highlands are the source area for the waters of the Blue Nile River—a tributary to the Nile of Egypt. As well as its geological exceptionalism, Ethiopia has a long and ancient cultural and religious history.
DANAKIL DEPRESSION AND EAST AFRICAN RIFT
Of great interest to geologists is the Danakil Depression a vast, elongate, north-south oriented depression located in the extreme northeast corner of Ethiopia, bordering Djibouti and Eritrea. The base of the depression drops to about 375 feet below sea level. Here, at about 8 degrees north of the equator, solar radiation is intense and cooling winds are blocked in by the steep surrounding cliffs of the depression. But besides those sources of heat, hot Earth Mantle materials i.e. magma, wells up below the rocks at the base of the depression. These geothermal sources of heat are a source of heat as well as magma..and when it exits onto the surface—of lava of volcanoes, lava of flood basalts and the heat of hydrothermal fields which produce steaming gysers, hot springs, hot mud pools, and colorful salt deposits dissolved by the hot water from surrounding bedrock. The Danakil Depression is often claimed to be the hottest place on Earth, where temperatures often average about 35C (95 F) and may often reach 48C (118F).
The Earth’s rigid rocky continental crust is composed of low density, lighter colored silica-aluminum rich (felsic) rocks which form the crust which is between 9-12 miles thick. The ocean crust is thinner and composed of mafic or dark colored, dense, iron-magnesium rich rocks. Below the solid crust lies the hot mantle which is comprised of mafic “magma”, which is so hot that at the surface (where pressure is low) it can flow like hot asphalt—though its temperatures are much higher. Mantle material is cooler near the base of crust at about 500 C-1000C but heats up to about 4,000 C at depth..
Like a heated pot of maple syrup, hot syrup in the bottom of the pot is buoyant and rises toward the surface. In the Earth’s deep mantle magma is eight times hotter than that near the surface. Hot plumes are buoyant and rise toward the crust- mantle boundary. There, these hot plumes (some claim the existence of “super plumes”) can push up or “dome” the crust. These cause elevated surface features such as highlands and plateaus (See Ethiopian Plateau and the Ahmad Mts in Ethiopia) and bordering these domed up structures are regions of earth fracturing such as the Danakil Depression and the Great Rift Valley.
Magma arising as it does from depth is hot @ 3,000-4,000 C. At the crust-mantel boundary it comes in contact with felsic crustal rocks (Granite a felsic rock can melt at 1,220C-1,300C) which the hot plume may partially melt. This molten felsic rock material may drain away from the overlying crust (1) causing thinning of the crust and making it more subject to fracturing and (2) form pools of molten magma which can undergo physical and chemical alteration.
HAYLI GUBBI
How did Hayli Gubbi become an explosive volcano? The magma chambers of explosive volcanoes are composed of felsic magma rich in silica and water. But most of the base rocks in this region are mafic. Some theorize that as plumes of maga rise toward the crust they may melt some of the overlying rock (‘plume head melting process”) to form a magma pool (or magma chamber) below the surface where chemical changes and other processes can alter the mineral composition over time. Mafic magmas can undergo physical and chemical reactions (called fractional crystallization) to form more silica, water and gas rich felsic magmas. Were that to happen below Hayli Gubbi that might result in more viscous, gaseous and violent eruption prone magma to form in its magma chamber. Perhaps this is the source of the violent eruption of Hayli Gubbi.
FLOOD BASALTS
Crustal fractures resulting from the doming and thinning caused by magma plumes may produce elongate crust fractures which may release the hot magma through long fissures in the crust to the surface. The lava may spread out to cool and solidify forming a low-slope lava terrane covering vast areas of the Earth’s surface. These areas covered in volcanic lava flows are called “flood basalts” (Note that fine grained mafic rocks are classed as basalt). In the USA state of Washington, ancient Columbia River flood basalts cover vast areas estimated to have spread over more than half of that state. Similar features are found in Siberia (Siberian Traps) and India (Deccan Traps)
If the rising magma finds a narrow fissure through the fractured crust which reaches the surface it may generate a shield cone type volcano such as Mona Loa and Kilauea in Hawaii and Erta Ali in Ethiopia. These volcanoes erupt from a magma source of mafic, hot, highly fluid low-gas-low silica magma. They form low slope “scab like” or shield like eruptions on the surface.
Note: Lower Mantle= 4,000C, compare to Sun surface which is @ 5,500 C
*PANGAEA
A supercontinent which formed in Paleozoic and began to break apart—in similar fashion to that what we are observing in the Afar Triangle A hotspot formed somewhere along the boundary between what is now Africa and South America pushing up and thinning the crust and subcrustal magma currents generated by the upwelling plume slowly caused the break up of the supercontinent.
Today continents comprise about 29% of Earth surface and ocean covers about 71% with most (2/3) of the continents spread across the Northern Hemisphere. Between about 300mya to 200 mya years ago…all of Earth’s continents were cobbled together into one giant “C” shaped continent called Pangaea. Pangaea covered an area of about one-third of the Earth surface in a more or less north-south orientation with the remaining two-thirds, an ocean called Panthalassa. There was no Atlantic, Indian or Arctic Ocean—only Panthalassa. At its widest part Pangaea, may have been @ 6,300 miles from west to east coast, creating a Panthalassa of as an uninterrupted @18,600 miles of open ocean. Compare that to today’s 12,300 miles wide ocean of the present Pacific Ocean. .
Pangaea’s core area was located close to the equator, while other parts stretched toward the higher latitudes in a “C” shape with no polar ice caps. As a result of its orientation, a great central desert formed near the equator. Land dwelling animal and plant species of that era were spread widely across the continents, and ocean currents and winds were altered as well.
But the Earth did not remain with only a single supercontinent. About 200 million years ago fissures developed in the central part of Pangaea and the “supercontinent” began to split apart.
NB note; End of Paleozoic @ 250 mya, 250=66 mya Mesozoic, 66 mya to present Cenozoic…Pleistocene 2.6-mya to 12,000 ya
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