Formation of Volcano on Earth and their Types of Eruption

Formation of Volcano: Volcanoes, the ruptures in Earth’s crust, have played a vital role in shaping our planet for over 4 billion years. They are the remarkable geologic architects that have contributed to over 80 percent of Earth’s surface. Through their explosive eruptions, volcanoes have sculpted majestic mountains and created awe-inspiring craters.

The flow of hot lava has transformed barren landscapes, giving birth to rivers of molten rock that solidify into unique formations. Yet, the true significance of volcanoes lies beyond their raw power. Over time, the elements weather the volcanic rocks, releasing vital nutrients and minerals trapped within, resulting in remarkably fertile soils.

These nutrient-rich soils have provided a foundation for thriving ecosystems and enabled civilizations to flourish. Volcanic regions have become hotspots for agricultural productivity, supporting diverse plant and animal life.

Volcanic on Earth

• Volcanism on Earth occurs in various geologic settings.
• The majority of active volcanoes and related phenomena are found at plate boundaries.
• Convergent plate boundaries, where two plates collide, are a primary site of volcanism. One plate is forced beneath the other into the mantle, resulting in volcanic activity.
• Another significant site of volcanism is along the oceanic ridge system, where plates move apart, and magma rises from the mantle. This creates new oceanic crust and is predominantly underwater.
• Subaerial volcanism occurs when the oceanic ridges emerge from the ocean, allowing volcanic activity on land.
• Roughly 80 percent of active terrestrial volcanoes are located at convergent plate boundaries.
• Oceanic ridges account for a substantial portion of volcanic activity, primarily underwater.
• Volcanism at these sites is driven by the movement and interaction of Earth’s tectonic plates.
• The process involves the release of magma, lava, volcanic ash, and gases from a magma chamber beneath the Earth’s surface.
• Volcanic activity can lead to the formation of mountains, craters, and the creation of new land through the deposition of lava and volcanic materials.

Formation of Volcanic

Volcanoes and Tectonic Plates:

These are the key points regarding the formation of volcanoes along tectonic plate boundaries and hotspot volcanism.

• Majority of Volcanoes: Most volcanoes on Earth are formed along the boundaries of tectonic plates. These plates are large pieces of the Earth’s lithosphere that are in constant motion, interacting with one another.

• Subduction Zones: When tectonic plates collide, one plate can be forced beneath another in a process called subduction. As the descending plate sinks deep into the Earth, it experiences increasing temperatures and pressures, causing the release of water from the rocks.

• Water Release: The water released from the rocks in the subduction zone slightly lowers the melting point of the overlying rock. This reduction in melting point leads to the formation of magma, which can eventually rise to the surface and give rise to volcanic activity.

• Spark of Life: The release of magma from the subduction zone can reawaken a dormant volcano, providing the necessary “spark of life” for its eruption.

• Hotspot Volcanism: Not all volcanoes are formed due to subduction. Another mechanism is hotspot volcanism. In this case, a hotspot—a region of intense magmatic activity—exists in the middle of a tectonic plate.
• Pushing Up through Crust: The hotspot pushes up through the Earth’s crust, forming a volcano. While the hotspot itself is believed to be relatively stationary, the tectonic plates continue their slow movement, resulting in the formation of a volcanic chain or a series of islands on the Earth’s surface.
• Hawaii Volcanic Chain: The volcanic chain in Hawaii is often attributed to hotspot volcanism. As the Pacific Plate moves over the Hawaiian hotspot, a string of volcanoes has been formed, with each island representing a different stage in the volcanic activity.

 Eruption Types

The six eruption types are in order from least explosive to the most explosive; Icelandic, Hawaiian, Strombolian, Vulcanian, Pelean, and Plinian.

Icelandic

• Icelandic, flood, or fissure eruptions refer to volcanic eruptions that release massive amounts of hot, runny lava, which floods the Earth’s surface.
• These eruptions occur through long cracks in the surface known as fissures, which can extend up to 15 miles in length.
• The resulting volcanic cones from these eruptions are known as shield cones.
• Shield cones are characterized by their low and broad shape, unlike the steep and conical shape of stratovolcanoes.
• During Icelandic eruptions, volcanoes may erupt multiple times over the same area, leading to the formation of extensive lava plateaus.
• The Deccan Plateau in India is an example of a lava plateau formed by Icelandic eruptions. It spans approximately 100,000 square miles, slightly smaller than the state of Montana.
• The Columbia Plateau in the western United States is the largest lava plateau globally, covering nearly 100,000 square miles. It reaches a thickness of almost a mile in certain areas.

Hawaiian eruptions

It’s important to note that while there are similarities between Hawaiian and Icelandic eruptions, the differences in eruption style and resulting volcanic formations contribute to unique geological features in each region.

Similarities

• Hawaiian eruptions and their similarities and differences compared to Icelandic eruptions
• Hawaiian eruptions share similarities with Icelandic eruptions.
• Both types of eruptions involve multiple fissures through which lava is brought to the surface.
• Both eruption types are known for their spectacular fire fountains.

Differences

• In Hawaiian eruptions, the greatest quantity of lava typically pours out from the main vent at the summit of the volcano, rather than alongside fissures.
• Hawaiian eruptions tend to result in the formation of steeper and higher volcanic cones.
• The volcano formed from Hawaiian eruptions is often characterized by a distinct cone shape.

Strombolian eruptions

Strombolian eruptions are more explosive compared to Icelandic and Hawaiian eruptions. These points summarize the main features of Strombolian eruptions, including their explosive nature, the absence of significant lava flows, and the formation of steep-sided cinder cones.

• These eruptions are named after the volcanic island of Stromboli, located off the coast of Italy, which has been erupting consistently for centuries.
• Strombolian eruptions are characterized by short-lived explosive events that occur at regular intervals, often around every 20 minutes.
• During a Strombolian eruption, thick and pasty lava is forcefully ejected into the air, along with bursts of steam and gas.

• These eruptions typically produce little to no lava flow.
• The volcanic cones formed as a result of Strombolian eruptions are known as cinder cones.
• Cinder cones are steep-sided cones composed of fragmented volcanic material.

Shield volcanoes

• Shield volcanoes are a type of volcano characterized by their wide and low slopes.
• They are the largest volcanoes in the world, extending to great heights and distances.
• The lava flows from shield volcanoes can reach far distances. The Hawaiian volcanoes are famous examples of shield volcanoes.
• Shield volcanoes consist almost entirely of frozen lavas and have a shape resembling a warrior’s shield, hence the name.
• These volcanoes are primarily composed of basalt, a type of lava that is less viscous and very fluid when erupted.
• Due to the fluidity of basaltic lava, shield volcanoes have gentle slopes and are not steep.
• Shield volcanoes are typically low in explosivity. However, if water enters the vent, they may become explosive.
• The lava from shield volcanoes often moves in the form of fountains, which can throw out cones at the top of the vent and develop into cinder cones.

Cinder cone volcanoes

• Cinder cone volcanoes are small-sized volcanoes.
• They are composed mainly of loose, grainy cinders, which are extrusive igneous rocks. Another term for cinders is scoria.
• Unlike shield volcanoes, cinder cone volcanoes have little to no lava present.
• Cinder cone volcanoes are characterized by their steep sides, which give them a cone-shaped appearance.
• These volcanoes typically have a small crater at the top, which is the result of explosive eruptions.
• The cinders, or scoria, are fragments of volcanic rock that are ejected into the air during the eruption and fall back to the ground, building up the cone-shaped structure.
• Cinder cone volcanoes are often formed from short-lived, explosive eruptions.

Vulcanian eruptions

• Vulcanian eruptions are more violent and explosive compared to Strombolian eruptions.
• These eruptions are named after the island of Volcano off the coast of Italy, which also gave the term “Volcano.”
• Vulcanian eruptions are characterized by the emission of high dark clouds consisting of steam, ash, and gas.
• The ash plume produced during Vulcanian eruptions takes on a cauliflower-shaped head and a thinner, more tree trunk-like base.
• After the eruption of ash and gases, Vulcanian eruptions can also eject thick and pasty lava.
• The volcanic cones formed by Vulcanian eruptions are typically steep-sided and more symmetrical compared to cinder cones.
• These more symmetrical cones resulting from Vulcanian eruptions are referred to as “stratovolcanoes.”
• Vulcanian eruptions can generate ash plumes reaching heights of 2-9 miles.
• The photo mentioned is of the 1918 eruption of the Katla volcano in Iceland, which provides an example of Vulcanian eruption activity.

Stratovolcanoes

• Stratovolcanoes, also known as composite cones, are formed through a combination of explosive eruptions followed by lava ejections.
• The initial phase of a stratovolcano involves explosive eruptions that eject significant amounts of steam, gas, and ash into the atmosphere.
• After the explosive phase, the volcano undergoes lava eruptions, resulting in the deposition of layers of ash and lava.
• Stratovolcanoes are characterized by their tall and steep profiles, with a conical shape.
• They are the most common type of volcanic cone found on Earth.
• Many famous stratovolcanoes exist worldwide, including Mt. St. Helens and Rainier in Washington, Mt. Fuji in Japan, Mt. Pinatubo in the Philippines, and Mt. Etna in Sicily.
• Stratovolcanoes are typically associated with explosive eruptions and can pose significant hazards, including pyroclastic flows, lahars, and ashfall.

Pelean eruptions

Pelean eruptions and the catastrophic eruption on the island of Martinique in 1902:

• Pelean eruptions are highly dangerous and explosive volcanic eruptions.
• The name “Pelean” is derived from the devastating eruption that occurred on the island of Martinique in the Caribbean Sea in 1902.
• The eruption unleashed a pyroclastic flow, which is a fast-moving mixture of hot gases, ash, and volcanic materials.
• The eruption and subsequent pyroclastic flow resulted in the almost instantaneous death of approximately 29,000 people.
• During a Pelean eruption, “glowing clouds” comprised of gas and ash race down the mountainside at speeds exceeding 70 miles per hour.
• The pyroclastic flow is so heavily laden with ash that it becomes denser than air and hugs the ground as it approaches the coast.
• The temperatures within the pyroclastic flow were estimated to be around 700 degrees Fahrenheit (370 degrees Celsius), causing total devastation in its path.
• Astonishingly, the sole survivor of the Martinique eruption was a prisoner who was confined in a thick-walled cell with its only door facing away from the explosion.
• These points underscore the extreme danger and explosiveness associated with Pelean eruptions, as exemplified by the catastrophic eruption in Martinique in 1902. The eruption’s devastating pyroclastic flow, high speeds, heavy ash content, and scorching temperatures resulted in a massive loss of life, with only one individual surviving due to being imprisoned in a specific cell configuration.

Plinian eruptions

Plinian eruptions are the most explosive type of volcanic eruptions.

• The name “Plinian” is derived from Pliny the Elder, a Roman author and naturalist who died during the eruption of Mt. Vesuvius in 79 A.D.
• Plinian eruptions are characterized by a very high ash cloud that can rise upwards of 50,000 feet (almost 10 miles) into the atmosphere.
• These eruptions often produce deadly pyroclastic flows, which are fast-moving currents of hot gases, ash, and volcanic materials.
• The eruption of Mt. St. Helens on May 18, 1980, was a notable example of a Plinian eruption. The ash cloud generated by the eruption reached a height of over 50,000 feet.
• Another famous example of a Plinian eruption is the eruption of Mt. Vesuvius in 79 A.D., which resulted in the destruction of the ancient Roman cities of Pompeii and Herculaneum. The eruption caused hot ashfalls that buried the cities, leading to the tragic loss of thousands of lives.
• Plinian eruptions are characterized by their explosive nature, high ash cloud formation, and the potential for devastating pyroclastic flows.

Intrusive and Extrusive Volcanism

As per the movement of magma, volcanism can be classified into both intrusive and active volcanism.

Intrusive Volcanism

Intrusive volcanism is when magma is forced into the rocks that make up the Earth’s crust. When it cools and becomes solid while still underground, different features called plutons are formed. The rock formed is an intrusive igneous rock.

These plutons will be exposed at the surface of land when the overlying rocks are removed after a long time of denudation (laid bare by erosion).

The cooling and solidification of magma can happen both inside the earth and over the surface of the earth. In the process the following types of magma-based landforms are created inside of the earth:

• Batholiths: A formation of large-scale magma that has been solidified at the base of a mountain.
• Laccoliths: A small-scale magma that pushes the overlying layers of rocks to form a dome-shaped structure.
• Lapoliths: It is a small-scale magma cooled near the earth’s surface that lies horizontally to the existing rocks.
• Phacoliths: A phacolith is a pluton of igneous rock parallel to the bedding plane or foliation of folded country rock.
• Sills/Sheets: This is a small-scale magma cooled near the earth’s surface that lies horizontally to the existing rocks.
• Dikes: Is a small-scale magma cooled within the earth’s crust that stands vertically to the existing rocks.

Extrusive volcanism

Extrusive volcanism occurs when molten magma, under high pressure, reaches the Earth’s surface through fissures in the underground rocks. This volcanic activity gives rise to various landforms known as “igneous extrusions.” Extrusive volcanism and the associated landforms provide valuable insights into the Earth’s geothermal activity and volcanic processes. They also contribute to the formation of unique landscapes and play important roles in geothermal energy production and tourism.

Caldera: A caldera is a large, basin-like hollow that forms shortly after the emptying of a magma chamber or reservoir during a volcanic eruption. It results from the collapse of the ground above the emptied magma chamber. When a caldera is filled with water, it is referred to as a “caldera lake.” Examples of famous calderas include Crater Lake in Oregon, USA, and Lake Toba in Sumatra, Indonesia.

Composite Cones: Composite cones, also known as stratovolcanoes, are large volcanic mountains formed by layers of solidified lava and volcanic ash accumulating over time. These volcanoes typically have steep slopes and can reach great heights.

Geysers: Geysers are vents in the Earth’s surface that periodically eject columns of hot water and steam. They occur in areas with underground geothermal activity, where heated water is trapped and periodically released due to pressure buildup.

Hot Springs: Hot springs are springs produced by the emergence of geothermally heated groundwater from the Earth’s crust. These springs occur in areas with geothermal activity and are known for their higher temperatures compared to surrounding groundwater. Hot springs often have mineral-rich waters and can create unique ecosystems.

Volcanic Activity – Points to note down

• Volcanoes are often associated with areas of intense folding and faulting.
• They can be found along coastal mountain ranges, on islands, and in the middle of oceans.
• The interior parts of continents generally do not experience volcanic activity.
• The Pacific region, also known as the Pacific Ring of Fire, is home to a majority of the world’s active volcanoes.
• The Pacific Ring of Fire is characterized by a high concentration of volcanic eruptions and seismic activity.
• This region stretches in a horseshoe shape from the western coast of North and South America to the eastern coast of Asia, including the Philippines, Indonesia, Japan, and New Zealand.
• The Ring of Fire is associated with several tectonic plate boundaries, including the Pacific Plate, the Philippine Sea Plate, and the Indo-Australian Plate, which leads to the frequent occurrence of volcanic activity.
• The volcanic activity in the Pacific Ring of Fire is a result of subduction, where one tectonic plate is forced beneath another, creating intense heat and pressure that leads to magma generation and volcanic eruptions.
• The volcanoes in the Pacific Ring of Fire can range from explosive stratovolcanoes, such as Mount St. Helens in the United States and Mount Fuji in Japan, to shield volcanoes like Mauna Loa in Hawaii.
• The volcanic activity in this region poses significant hazards, including lava flows, pyroclastic flows, ashfall, lahars (mudflows), and volcanic gases, which can have impacts on nearby communities, infrastructure, and the environment.

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