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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