Tribune Print Share Text

Title

Volcanoes

Their beauty, their danger

Created date

March 22nd, 2018
photo of an erupting volcano

Volcano erupting!

They are beautiful, terrifying, and deadly. Volcanoes pepper the Earth’s surface.

Within the last 10,000 years, scientists have found evidence of some 1,500 land volcanoes that appear to have been active at some point in time—600 of them having blown in the span of recorded history. The number of underwater examples is practically too many to count.

The question remains, however: What are these majestic, yet catastrophic, giants?

Volcanoes are the product of the planet’s crust, which is broken into 17 tectonic plates.

In fact, fault lines—where Earth’s plates rub together—lace the globe.

Deep within the planet, conditions are extremely hot. At its core is a roiling, lava-like mass that emanates enormous heat and pressure, causing the upper layers of the planet’s crust to shift.

The faults that separate these plates become fissures through which Earth’s intense inner heat and liquid magma vent and ooze. The result is a mountain that acts much like a pimple on the face of our planet.

Volcanoes have been erupting for ages. Perhaps history’s most famous and deadly example is Mount Vesuvius, located near the Ancient Roman town of Pompeii.

On August 24, 79 A.D., Vesuvius blew its top with so much force that scientists believe it threw rock, scorching gasses, and ash 21 miles high.

The eruption, which lasted an entire day, dropped roughly six inches of ash every hour and killed an estimated 16,000 people in Pompeii and nearby Herculaneum. The incredible part is that, with knowledge, the victims actually would have had plenty of warning.

The early signs came by way of multiple earthquakes, one of the biggest hitting in 63 A.D.  Ironically, though, the denizens of Pompeii were still repairing the damage when Vesuvius erupted.

Earthquakes are often warnings in themselves because they signify a disturbance in Earth’s surface. As the planet’s crust shifts under the tension and pressure of its hot, liquid core, these forces rise up and, especially in mountainous regions, spew forth.

Different types

While the most popular image of a volcano is of the open-topped mountain, there are many different types.

Some, for instance, are mountainous formations but without the crater at the peak. This is due to lava that oozed so slowly during an eruption that it cooled at the structure’s top, hardening, and therefore, closing it off.

Others, known as shield volcanoes because of their resemblance to Ancient Greek warrior shields, are the result of long-flowing lava fields. Unlike stratovolcanoes, which blow their gasses and lava high into the atmosphere, shield volcanoes slowly but surely spill over.

Their lava, in turn, drifts outward in a series of rivulets that eventually accumulate into a shield-shaped mound, thus creating a volcanic formation.

Another species of volcano, this one present on the U.S. mainland, is called a cryptodome. In this case, subterranean pressures drive lava upward, forcing a mountain’s surface to bulge.

The massive 1980 eruption of Mount St. Helens in Washington State is an example.

But considering a volcano’s potentially deadly effects, warning is of the utmost importance. The people of Pompeii and Herculaneum had signs but possessed neither the knowledge nor the technology to recognize and heed them.

Today, things have changed quite a bit.

Modern warning systems

The United States Geological Survey (USGS), for one, uses a nationwide system that classifies the level of volcanic activity at domestic formations like Mount St. Helens. This system employs continual volcanic activity observation at known sites based on factors such as volcanic mudflows, evidence of airborne ash, or lava flows.

Depending on the amount of activity and the recorded characteristics of a particular site, the USGS may issue any one of four warnings: Normal, connoting brief activity that has totally subsided; Advisory, meaning that volcanic activity has settled but persisted; Watch, which entails heightened unrest; and Warning, when an eruption is clearly under way.

To be sure, such warning systems probably come as a comfort to those living in the potential path of destruction. But volcanoes are definitely here to stay.

Comments