In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such that expelled lava violently froths into volcanic ash when

2024年1月16日 · Here are five of the most explosive volcanic disasters throughout history and where they rank on the volcanic explosivity index (VEI) — a scale used to measure how much volcanic material erupts from the volcano, how high the volcanic matter extends into the atmosphere and how long the eruption lasts.

Volcanic eruptions can be explosive, sending ash, gas and lava high up into the atmosphere, or the magma can form lava flows, known as effusive eruptions. Whether an eruption is explosive or effusive largely depends upon the amount of gas in the magma.

2023年12月8日 · Eruption of lava flows is the dominant style of activity at Kīlauea today, but layers of fragmented rocky deposits on the volcano record many explosive eruptions during the past 2,500 years. For example, between about 1500 and 1800, at least a dozen pyroclastic surges swept across the summit area.

2025年1月22日 · Effusive eruptions involve the outpouring of basaltic magma that is relatively low in viscosity and in gas content. Explosive eruptions generally involve magma that is more viscous and has a higher gas content. Such magma is often shattered into pyroclastic fragments by explosive gas expansion during an eruption.

Most explosive eruptions occur in volcanoes above subduction zones, where one tectonic plate dives beneath the other. Eighty to 120 kilometers below the surface, magma forms when the rocks of the mantle melt just above the subducting plate. The magma rises through the mantle, and erupts to form great composite volcanoes such as Vesuvius.

2021年1月11日 · An explosive eruption produces huge clouds of volcanic ash. Chunks of the volcano fly high into the atmosphere. Explosive eruptions can be tens of thousands of times as powerful as an atomic bomb (Figure below). Hot magma beneath the surface mixes with water. This forms gases. The gas pressure grows until it must be released. The volcano erupts ...

Explosive eruptions can occur when viscous magma, such as rhyolite or andesite, erupts at the surface. The eruptions are powered by expanding volcanic gases, and by expanding steam if magma interacts with water. Explosive eruptions yield pyroclastic material consisting of ash and coarser debris thrown into the air.

Some volcanic eruptions consist of mostly gas emissions, others are relatively quiet discharges of fluid lava, and yet others are cataclysmic explosions. Different kinds of eruptions leave characteristic deposits that, in turn, build different types of volcanoes.

Effusive eruptions build up gently-sloping Shield Volcanoes like Hawaii. Explosive eruptions occur where cooler, more viscous magmas (such as andesite) reach the surface. Dissolved gases cannot escape as easily, so pressure may build up until gas explosions blast rock and lava fragments into the air!