The largest volcanic eruptions of the 20th century are relatively well known.
Novarupta in 1912. Mount Saint Helens in 1980. Pinatubo in 1991.
However, there is another large eruption that is often forgotten about in Central America.
The eruption in question was the 3rd largest of the 20th century, and occurred from the Santa
Maria Volcano in 1902. Today, this volcano is erupting once again. This video will discuss
this active volcano, its massive eruption, and mention what its future hazards are.
The Santa Maria volcano can be found in the southwest portion of Guatemala,
where it is located 11 kilometers south of a major city known as Quetzaltenango.
Santa Maria is a relatively recent volcano, as it began forming 103,000 years ago when magma
related to plate subduction off the southern coast of Guatemala reached the surface.
The initial eruptions at Santa Maria were relatively explosive, but the composition
of lava was completely different than what is witnessed at the volcano today. These eruptions
produced a type of low silica volcanic rock known as basalt. Over the next 30,000 years, continued
eruptions slowly built the volcano's main summit with overlapping layers of lava and ash.
However, by 72,000 years ago, the composition of lava had changed. The type of lava which erupted
onto the surface now created lighter colored basaltic andesite instead of basalt. This
change in composition was marked by a series of eruptions which outputted a significant quantity
of lava in a short timespan. By 35,000 years ago, the summit of Santa Maria
had finished its construction, and stood at a height of 3750 meters above sea level.
Over the next 10,000 years, eruptions continued on the outskirts of the main cone through a
series of viscous lava flows on the flanks of Santa Maria. After the last of these eruptions,
the volcano became dormant for 25,000 years. During this period of time, the composition of
lava at depth changed and once again became more siliceous. Basaltic andesite became andesite,
which then became dacite. This highly siliceous magma caused pressure
to build beneath the volcano. Then, in April of 1902, a major earthquake hit near the volcano.
This magnitude 7.5 earthquake signaled that Santa Maria had awoken from its long dormancy.
Then, on October 24th at 17:00 local time, an incredibly loud noise was heard in central
Guatemala. This noise lasted for 5 minutes, and was described as similar to the loud roar of a
waterfall. Although it wasn't known at the time, what had just happened was the southwest flank
of Santa Maria had collapsed in a massive landslide. As a plume of ash was carried 34
kilometers into the atmosphere, pyroclastic flows raced downhill from the volcano.
Structures that were not destroyed by this pyroclastic flow were soon damaged as hot bombs
of lava began falling in a 14 kilometer radius. In total, 10 cubic kilometers of tephra
had been ejected from the volcano, marking it as the third largest eruption of the entire 20th
century. Although Santa Maria had not lost much height, it now had a massive scar in its southwest
flank which measured more than a kilometer across. In the aftermath of this eruption, small
explosions continued for another decade. Then, in 1922, dacite lava began erupting onto the surface.
This eruption still continues today, and over a century has created a series of overlapping
lava domes referred to as Santiaguito. Although the current eruption from Santa
Maria is considered to be relatively small, it still presents a number of hazards.
These hazards are significant enough that the United Nations designated Santa Maria as one of
the 16 most dangerous volcanoes on the planet by classifying the mountain as a "decade volcano".
Due to the frequent rainfall in the region, ash from eruptions are frequently swept downhill in
what is termed a lahar. These lahars are similar to flash floods, and have twice destroyed the town
of El Palmar. Another hazard is that every time Santa Maria produces a small explosion,
there is a chance that one of its lava domes could collapse and generate a pyroclastic flow.
The resulting pyroclastic flows could travel up to 10 kilometers. However,
the most significant hazard at Santa Maria is due to the unique scar caused by its 1902 eruption
which has left part of the volcano over steepened and prone to collapse. If it were to collapse,
the resulting landslide would travel outwards in every direction, impacting dozens of nearby
cities with large populations. Although this scenario is considered unlikely in the short term,
it cannot be truly ruled out in the long term. I hope that you enjoyed this video. If
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