What is Shield volcanoes, How it formed?
A shield volcano is a type of volcano named for its low profile, resembling a warrior’s shield lying on the ground. They are the largest volcanoes on Earth, and some of the most fascinating geological features on our planet.
Formation of Shield Volcanoes:
Shield volcanoes are formed by the eruption of highly fluid (low viscosity) lava, typically basalt. This type of lava flows easily and can travel long distances from the vent before cooling and solidifying. As numerous eruptions occur over time, layer upon layer of lava builds up, gradually creating the broad, gently sloping sides that characterize shield volcanoes.
Here’s a breakdown of the formation process:
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- Magma Chamber: Beneath the Earth’s surface, molten rock called magma collects in a chamber.
- Low Viscosity Magma: In the case of shield volcanoes, the magma is typically basaltic, which is less viscous (thicker) than other types of magma, allowing it to flow more easily.
- Eruption: The low-viscosity magma erupts from the vent and spreads out over a large area, forming thin lava flows.
- Solidification: As the lava cools and hardens, it forms a solid rock layer.
- Repeated Eruptions: Over hundreds of thousands, even millions of years, this cycle of eruption, spreading, and solidification repeats itself, gradually building up the volcano’s size and shaping its characteristic shield-like form.
Key characteristics of Shield Volcanoes:
- Gentle slopes: Due to the fluid nature of the lava, shield volcanoes have slopes that are typically less than 10 degrees. This is in stark contrast to stratovolcanoes, which have steeper slopes due to the accumulation of alternating layers of lava and ash.
- Large size: Shield volcanoes are the largest volcanoes on Earth. Mauna Loa in Hawaii, for example, is over 4,169 meters (13,677 ft) tall from its base on the ocean floor and encompasses an area of over 52,750 square kilometers (20,370 sq mi).
- Caldera: Many shield volcanoes have a caldera, which is a large depression at the summit formed by the collapse of the volcano’s peak.
Which type of Lave forms Shield Volcanoes
Shield volcanoes are primarily formed by basaltic lava.
Here’s why:
- Basalt’s Low Viscosity: Basalt is a type of lava with a low viscosity, meaning it’s relatively thin and runny. This characteristic allows it to flow easily over long distances from the volcanic vent before solidifying.
- Spreading and Building Layers: The fluidity of basaltic lava enables it to spread out into broad sheets, contributing to the wide, gently sloping sides of shield volcanoes. As repeated eruptions occur, layer upon layer of this basaltic lava builds up, gradually constructing the volcano’s massive form.
