A volcano is a vent or fissure in the Earth’s crust that allows molten solids, liquids and gases to escape from the interior of the planet. The word “volcano” applies not only to the eruption of material but also to the conical mountain formed from the material previously expelled during eruptions. The volcano has a cup-shaped depression in the center which leads to the vent. The vent leads downward toward the earth’s core and provides an outlet for the magma (molten rock) and gases.
Volcanoes can be either on the surface or undersea. Undersea volcanoes are very misleading since, like an iceberg, the majority of the volcano is unseen below the water. The highest mountain on earth is the Mauna Loa volcano on Hawaii. The volcano is over 14,000 feet above sea level; however it stretches another 16,000 feet below the water to the seabed. (By comparison, Mount Everest is just over 29,000 feet, all above ground.)
Volcanoes are normally considered active, dormant or extinct. Due to the geological age of the Earth and volcanoes and the recorded history of various locations on Earth, there is no precise definition of these terms. A volcano is normally considered active if it is either currently erupting or showing signs of restless activity such as earthquakes or significant gas discharge. A volcano is considered dormant if it is not currently active, but could erupt again in the future. An extinct volcano is a volcano which was active in the past; however, it is unlikely to ever erupt again in the future. Volcanoes are usually found where the Earth’s tectonic plates have collided or pulled apart, but not where two plates “slide” past each other.
Some of the very many dangers associated with volcanoes are: pyroclastic flows, airborne debris, toxic gases, lava flows, and possible tsunamis from undersea volcanic eruptions.
Believe it or not, there are benefits to be derived from volcanic activity. Some of the benefits include:
- Lands surrounding older dormant volcanoes have some of the richest soil on Earth.
- Geothermal energy from areas such as Yellowstone is being used as an alternative to petroleum.
- Volcanoes provide recreational sources for hiking, tourism, and scientific instruction.
- Sources for precious gems and metals.
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