The following blog is an excerpt from Active, Dormant, & Extinct Volcanoes of the National Park System by the National Park Foundation.
Scaling rocks that never peak, leaving a gaping hole capable of spewing rock, ash, molten lava, or boulders across the landscape. They’ve been known to end civilizations, or in modern times, cause flight pattern disruptions that lead to billion-dollar losses for airlines. Today, there are approximately 1,500 active volcanoes around the world. Many more are dormant or extinct. Though these fascinating landforms are not frequently discussed, they are more prevalent than one might expect. Of the 169 active volcanos existing in the U.S. today, many can be found within the boundaries of our national parks.
Put simply; volcanoes are areas where materials from within the earth come out. The material is fluid molten rock, or magma, which, once it reaches the surfaces, is referred to as lava. This material is originally part of the mantle, the largest layer in the Earth located beneath the outer crust.
Though the mantle is extremely hot, it remains solid in most cases due to extreme pressure. When the material does melt, magma forms and moves towards the outer crust. Once pressure has built, the magma pushes through a vent or fissure in the Earth’s surface, a weak area of the rock.
The Earth’s surface is cracked along several tectonic plates that are continually moving. Most active volcanoes form along the border of two plates. The plates create volcanoes and other geographical landforms based on the way they move against or alongside each other.
Scientists understand the causes of volcanoes but are still unable to predict the eruptions. They monitor signs such as earthquakes, deformation of land, or increased gas emission, all potential signs of an imminent eruption. Ultimately, the buildup of gas and pressure within magna results in an eruption, which can vary in type, from a slow emittance of lava to a devastating explosion of rocks and ash.
Continue reading Active, Dormant, & Extinct Volcanoes of the National Park System by the National Park Foundation here.