Types of volcanic eruptions

Understanding the Diverse World of Volcanic Eruptions

Imagine a world where nature’s fury is unleashed in myriad forms, each with its own unique characteristics and consequences. From the calm, effusive Hawaiian eruptions to the explosive Plinian events that can reach heights of 45 kilometers into the sky, volcanologists have meticulously classified these phenomena. Let’s dive into this fascinating realm and explore how different types of volcanic eruptions shape our planet.

Magmatic Eruptions: The Calm Before the Storm

Have you ever wondered what it’s like when magma decompresses, releasing gases that create a powerful eruption? This is precisely what happens in magmatic eruptions. These events are characterized by the release of gas within magma, leading to explosive activity. However, not all eruptions are as dramatic; some can be relatively quiet and effusive.

Hawaiian Eruptions: The Gentle Giants

When we think of Hawaiian eruptions, images of smooth, flowing lava come to mind. These eruptions are driven by the decompression of gas within very fluid basaltic magma. They often start as a line of vents along a fissure, creating what is known as a ‘curtain of fire.’ Central-vent eruptions can produce spectacular lava fountains that reach hundreds of meters into the air.

While these eruptions are generally calm and effusive, they have produced some of the most awe-inspiring geological formations. For instance, Pele’s tears—small glassy droplets formed during lava fountaining—and reticulite, a porous volcanic rock, are unique to Hawaiian activity. Despite their name, Hawaiian eruptions can be found in other locations too; Mount Etna in Italy once produced the highest recorded lava fountain.

Strombolian Eruptions: The Noisy Giants

Now, let’s shift our focus to Strombolian eruptions. These are characterized by short-lived and explosive eruptions of viscous basaltic lava. Think of it as a loud, noisy eruption where gas bubbles within the magma burst with a loud pop, ejecting lava high into the air.

Stromboli itself is named after these eruptions, but they can be observed in other volcanoes like Mount Etna and Parícutin in Mexico. These eruptions are similar to Hawaiian ones but produce fewer molten lava flows due to their explosive nature. The accumulation of small fragments builds cinder cones, creating well-ordered rings of tephra around the vent.

Vulcanian Eruptions: Explosive and Violent

Next up are Vulcanian eruptions, which involve the buildup of high gas pressure due to intermediate viscous magma. These eruptions are explosive, characterized by short-lived explosions that form lava domes. The deposits from these eruptions include large blocks and bombs near the source vent, along with fine-grained ash elsewhere.

Volcanoes like Sakurajima in Japan and Tavurvur in Papua New Guinea have shown Vulcanian activity at various times. These eruptions can be destructive, causing widespread damage due to their explosive nature and fast-moving pyroclastic flows.

Peléan Eruptions: The Fast-Moving Giants

Now, let’s talk about Peléan eruptions, named after the devastating 1902 eruption of Mount Pelée. These eruptions involve the collapse of lava domes, creating large eruptive columns and fast-moving pyroclastic flows that can travel at extreme speeds.

The 1951 eruption of Mount Lamington in Papua New Guinea resulted in over 3,000 deaths, while Mount Sinabung in Indonesia has been experiencing frequent pyroclastic flows since 2013. These eruptions are characterized by incandescent pyroclastic flows that can cause widespread destruction and loss of life.

Plinian Eruptions: The Skyward Giants

Finally, we have Plinian eruptions, which are among the most dramatic. These massive eruptive columns reach up to 45 kilometers into the atmosphere, often associated with volatile-rich dacitic to rhyolitic lavas. Major Plinian eruptions include Mount Vesuvius in AD 79 and Mount St. Helens in 1980.

These events are not just visually stunning; they can have far-reaching impacts. For instance, the Lake Toba eruption (Ultra-Plinian) around 75,000 years ago is estimated to have covered an area of up to 2,000 cubic kilometers with ash and pumice.

Phreatomagmatic Eruptions: The Water-Magma Interaction

Lastly, let’s explore phreatomagmatic eruptions. These occur when magma interacts with water, leading to explosive activity. Surtseyan eruptions are a prime example of this, named after the 1963 eruption that formed Surtsey island in Iceland.

Surtseyan eruptions involve shallow-water interactions between lava and water, resulting in explosive ash and pyroclastic surges. The densest part of these clouds is nearest to the vent, creating a wedge shape. Over time, they form maars and tuff rings, associated with single-vent eruptions or fractures along plate boundaries.

Submarine Eruptions: The Hidden Giants

Now, let’s turn our attention to submarine eruptions. These occur underwater, often near mid-ocean ridges, and can form seamounts that may break the surface and create volcanic islands. They are driven by processes like decompression melting of mantle rock and subducting plates adding volatiles to rising plates.

Submarine eruptions produce pillow lava, glassy flows, and volcaniclastic sediment rocks in shallow water. Eruption rates decrease as plate movement carries volcanoes away from their source. With over 100,000 deepwater volcanoes worldwide, examples include Kamaʻehuakanaloa, Bowie Seamount, and Axial Seamount.

Subglacial Eruptions: The Ice Giants

Finally, subglacial eruptions occur under glaciers at high latitudes. These events generate meltwater that can produce jökulhlaups (glacier outburst floods) and lahars. Early study of glaciovolcanism began with William Henry Mathews’ 1947 paper on tuyas in northwest British Columbia, Canada.

These eruptions begin with pillow lava formation, followed by glassy breccia and eventually columnar jointing as the lava cools slowly. Examples include volcanic activity in S. states and Alaska, such as Mauna Kea in Hawaii, Antarctica (2008), Iceland (Vatnajökull ice cap), and even on Mars.

Phreatic Eruptions: The Steam Giants

Lastly, phreatic eruptions occur when steam explodes from hot rock, fracturing surrounding rock and ejecting fragments. These eruptions are often weak but can be precursors to larger volcanic activity. Examples include Mount St. Helens, Taal Volcano, La Soufrière, Soufrière Hills volcano, Poás Volcano, Mount Bulusan, Mount Ontake, and Mount Kerinci.

Conclusion

The world of volcanic eruptions is vast and varied, each type offering a unique glimpse into the power and beauty of nature. From the calm Hawaiian flows to the explosive Plinian columns, these phenomena continue to shape our planet in profound ways. Understanding these eruptions not only helps us appreciate their beauty but also prepares us for the challenges they pose.