Volcanoes: Nature At Work
Nature can give us wonders sometimes. In the spring, flowers bloom. In autumn, gardens are a variety of colorful leaves. However, nature can also get quite violent, like when a volcano erupts.
On January 15th this year, an underwater volcano in the island nation and archipelago Tonga erupted with the explosive force of a nuclear bomb, sending shock waves around the world. The Hunga-Tonga-Hunga-Ha’apai volcano’s eruption in the South Pacific launched a towering mushroom cloud of ash and dust into the stratosphere and got heard in Alaska. It also triggered tsunamis that traveled thousands of miles and got seen throughout the Pacific. So how did a sound wave travel 6,000 miles, the equivalent of almost 10,000 kilometers? And more importantly, what was the science that created such a big eruption?
To understand a volcano, we need to look at the layers that make up Earth. For easier comparison, let’s look at an egg. The egg’s shell is Earth’s crust, the ground on which we live. Inside, the egg white is the mantle, a layer of molten rock. Lastly, we have the egg core. That equals Earth’s core, a molten layer of iron and nickel, the outer core, and an inner core, a solid ball. Temperatures here could be as hot as the sun’s surface. Now let’s meet magma, a molten mixture of rocks, metals, and various stuff. Sometimes, this substance could build up in big pockets underneath the crust, creating magma chambers, and gases create pressure. The magma gets spewed up when the pressure exceeds the weight of the rock above it. That could happen due to landslides or displacement of the rock, leaving the spot vulnerable to the pressurized magma below.
Think about when you shake a bottle of carbonized soda. The carbon dioxide in the bottle gets pushed to the surface, battling against the sides of the container, trying to break free. And with enough pressure inside, when you open the cap, the drink inside would come spewing out and is what happens inside a volcano. When the magma reaches the surface and contacts air, it’s known as lava. And every time the volcano erupts, the lava builds up around it. As the substance hardens, it turns into rock, and the volcano “grows.”
OK, so when volcanoes erupt, they can be equal parts amazing and terrifying. However, not all volcanoes are what most think they look like, cone-shaped and shooting lava towards space. Some are flat, with the magma inside flowing out, like syrup or honey. Others have multiple vents, and not all are in mountain ranges. There are volcanoes under ice or underwater like the Tonga one. There are three types of volcanoes. Active volcanoes constantly erupt. Dormant ones are active but don’t erupt as much. And then there are extinct volcanoes, which haven’t erupted in a long time, probably thousands or millions of years, and wouldn’t likely erupt again in the future.
Some volcanoes can build up so much pressure that it erupts simultaneously, spewing giant ash clouds that blanket the sky and flinging rocks. These are supervolcanoes, the worst of the worst, that could lead to famine, pollution of drinking water, and more disastrous outcomes. These eruptions can make the magma chamber underneath it collapse under its weight. Thankfully, blasts like the Tonga volcano don’t happen too often. And satellite images post-eruption show that the volcano and the surrounding island have disappeared. Currently, help is being sent from New Zealand and Australia, though that has proved difficult since the only cable providing communications and internet to Tonga was severed.
So back to the question: How did the explosion sound get heard that far away? Well, think of a foghorn. The horn’s low-frequency sound can travel very far. Higher frequencies get absorbed and filtered by the medium they travel through. In other words, high-pitched noises don’t travel far. However, the Tonga blast was so big that even a high-frequency signal audible to the human ear got able to travel such a distance. Data from University of Alaska Fairbanks researchers found that the sound wave from the blast was moving at roughly 700 mph, or more than 1,100 kph.
It seems by now that these volcanoes, and the surprises nature bring, could be catastrophic. But as technology to detect these sudden eruptions and the volcanologists that monitor them are getting better at predicting the movements of volcanoes, we maybe could evacuate residents before the ash and lava reach them. That’s the end of this production from the New News Newsminute. Thank you, and tune in next time for more explosive updates.