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Earth: Volcanic Planet

There are ~1,350 potentially active volcanos on Earth. In 2022 people flocked to see the spectacle of volcanic eruptions in Iceland, Hawaii, Tonga and Indonesia, 4 of the 74 confirmed eruptions of the year. Earth has been volcanically active since it formed 4.6 billion years ago. In the tumultuous origins of our Solar System Earth was a giant sphere of magma tens of millions of kilometers from Sol (aka the Sun, our star), and it slowly grew and cooled forming a crust that trapped heat deep in the core of the planet.

Earth's molten core continues to cool slowly, the deep heat rises causing rock to melt and the tectonic plates of the crust to move. When that liquid rock is at depth it is called magma, and once it reaches the surface it is called lava. Millions and millions of years of cooling magma and lava built up the crust, and some of it still breaks through to the surface as lava flows, ash clouds, and volcanic gases. We pay attention to volcanic eruptions because they are hazardous to human communities and health. Yet the Earth as we know it would not exist without volcanic eruptions.

The chemistry and viscosity (fluidity) of the magma/lava is dependent on the chemistry of the source rock that melted, the temperature of the liquid, and the gas contents. Low viscosity lava flows like rivers. After 815 years of volcanic slumber, Mt. Fagradalsfjall on the Reykjanes Peninsula of Iceland began to erupt in 2021, producing lava fountains and lava flows that captivated people for months until the erupted went dormant. In August 2022 Mt. Fagradalsfjall began to erupt again, and though is not currently producing lava (as of December 2022), it is being monitored closely because there is no question that Iceland will produce more eruptions.

Iceland is an island built of lava. It sits atop a plate tectonic divergent boundary AND a volcanic hot spot, both of which bring magma to the surface thereby allowing the volcanic pile to rise above the waves. In contrast, Hawaii only sits atop a hot spot (it is nowhere near a tectonic plate boundary) and yet the Big Island of Hawaii is home to Mauna Loa, the largest active volcano on Earth, which started erupting on November 27, 2022 for the first time since is went dormant in 1984.

Much like the eruptions of Iceland, Mauna Loa is producing rivers of lava, and building spatter cones as lava flung into the air falls down around the vent. Aside from the danger of coming in contact with more than 900 degree Fahrenheit lava flows, thin strands of lava cool in the air forming golden string of glass called ‘Pele’s hair’ that can be carried by the wind and embed in people’s skin, eyes, and lungs. VOG (volcanic smog) is also closely monitored because sulfur dioxide and fine particles of volcanic gas are very dangerous to breathe. Asa result, Mauna Loa is closed to visitors but the eruption can be viewed from a distance.

The 1984 eruption of Mauna Loa was witnessed and studied by Maurice and Katia Krafft, 2 of the most famous and influential Volcanologists ever. They documented eruptions around the world scientifically and through photography and videography. They furthered the science of volcanic hazard assessment and eruption prediction, saving thousands of lives even after they lost their own lives to a high viscosity pyroclastic (super-heated ash cloud) eruption from Mt. Unzen in Japan on June 3, 1991. The documentary “Fire of Love” now available through Disney +/Nat Geo chronicles the Krafft’s love story, their research, their adventures, and is a compilation of the photos and videos they took during their travels. There are no other volcanic eruption videos like them in the world. In my opinion it is one of the most beautiful movies every created – but I’m biased because I have love volcanos since I was 10 years old. The picture below of a Mauna Loa lava flow on March 25 1984 was taken by Katia Krafft.

Katia Krafft also took the following picture, named 'Pele Dancing', one of the most famous lava flow pictures in the world - that can be purchased as a poster from the Maurice and Katia Krafft Memorial Fund.

A high viscosity pyroclastic eruption similar to the event that killed the Krafft’s in 1991 just occurred on December 4th, 2022 at Mt. Semeru on the island of Java in Indonesia, one of the Earth’s most active and deadly volcanos. Hundreds of people evacuated before the pyroclastic eruption and there have been no reported deaths, a much better outcome than almost exactly one year ago on December 4th, 2021 when Mt. Semeru killed 13 people. This most recent December 2022 pyroclastic eruption was caught on camera.

An even larger eruption, in fact the largest eruption of the 21st century thus far, was recorded by cameras and satellites. Hunga Tonga-Hunga Ha’apai erupted on January 15, 2022 destroying the island just north of New Zealand. It caused a tsunami that was up to 295 feet tall, and the sound of the eruption was heard in Alaska. The eruption injected a huge amount of water into the atmosphere, increasing the water content of the stratosphere by 10%, and water is a greenhouse gas. The climatic effects of this eruption are still being studied.

Volcanoes play an important role in Earth’s ever changing climate, adding greenhouse gases and particulates to the atmosphere. Greenhouse gases in and of themselves are not bad, it’s just a Golidlock’s problem…if the greenhouse gas levels are too low the planet cools/freezes and if greenhouse gas levels are too high the planet heats up, so the levels need to be just right for the present ecosystem to be stable and thriving. Water and carbon dioxide are the most abundant greenhouse gases in Earth’s atmosphere, and both are emitted by volcanoes and human activity. Volcanos only emit ~0.6 billion metric tons of carbon dioxide into the atmosphere each year, while humans emit at least 60 times that, at more than ~35 billion tons each year. Carbon dioxide levels are now higher than they have been in 3.6 million years and they continue to rise. Volcanic activity over the last couple centuries cannot be the source of the rising atmospheric carbon dioxide, because there hasn’t been enough volcanic activity to account for the increased levels of carbon dioxide in the atmosphere, or the increased quantity of particulates.

During eruptions, volcanic particulates like ash block sunlight like little umbrellas, an effect referred to as sun dimming. Some of the pollution emitted by human activity is having similar effects. We produce particulates through combustion from cars and coal burning, and other forms of pollution. The particulates block some sunlight from reaching the surface, at the same time that we produce greenhouse gases that absorb and retain the solar heat energy that does make it to the surface. However, the greenhouse gases stay in the atmosphere for decades, so their heat retention lasts much longer than the sun dimming effect of particulates that only stay in the atmosphere for days to months.

The atmosphere is a delicate balance of energy coming in, energy absorbed, energy emitted, and energy reflected. The thermal and reflective properties of gases, liquids, and solid particulates vary and their combined effect determines how much energy is retained in the atmosphere. The nature of every delicate balance is change, and thus the atmosphere and climate is always changing. In the past truly catastrophic volcanic eruptions have caused rapid climate change, plunging the world into volcanic winter (Examples: 1257AD & 1815AD), but at the moment humans are having the greatest effect on the climate by injecting billions of tons of greenhouse gases into the atmosphere causing the atmosphere and oceans to heat up. Yet a volcanic eruption could happen at any time compounding the atmospheric effects of human activity. The Earth is full of surprises, and has been for 4.6 billion years of ongoing change.

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