Volcanism

Contents

VOLCANISM

TYPES AND CAUSES

A volcano is a fissure in the crust of the earth through which eruptions can release gases, ash, steam, molten rock, and other materials. These vents or openings are found in the portions of the crust in which the rock layers are not as strong.

One illustration of an endogenic process is volcanic activity. Different land forms, like a plateau or a mountain, can form depending on how explosive the volcano is.

Different types of volcano :-

Based on the type of eruption and the shape that developed at the surface, volcanoes are categorized.

Shield Volcanoes

They are wider and farther apart, but not very steep. They reach considerable heights and lengths.
Because the lava flows a great distance, they are the largest volcanoes in the world. The most well-known examples are the volcanoes in Hawaii.
Low-sloped shield volcanoes are almost entirely composed of frozen lava.
Shield volcanoes get their name from the fact that they resemble a warrior’s shield when you fly over top of them.
Less viscous basalt, which erupts with great fluidity, makes up the majority of the lava in these volcanoes. These volcanoes are therefore not steep.
Generally speaking, they are not very explosive, but if water manages to get inside the vent, they could explode.
As it approaches, the lava shoots out of the of the opening like a fountain and turns into a cinder cone.

Cinder Cone Volcanoes:

Extrusive igneous rocks are called cinders. Scoria is a more contemporary term for cinder.
little volcanoes.
There is hardly any lava in these volcanoes; all that is left are loose, grainy cinders.
They typically have a tiny crater on top and extremely steep sides.

Composite Volcanoes:

cone-shaped, with somewhat steep sides and occasionally a few tiny craters at the top.
Because these volcanoes are made of layered solid lava flows combined with layers of volcanic rock that resembles sand or gravel, known as cinders or volcanic ash, volcanologists refer to these as “strato-” or composite volcanoes.
A cooler, more viscous lava eruption than basalt is what distinguishes them.
These volcanoes frequently erupt violently.
Massive amounts of ashes and other pyroclastic debris fall to the ground with the lava.

Caldera:

These volcanoes are among the most explosive on the planet.
Because of their extreme explosiveness, they often collapse on themselves during eruptions rather than erecting tall structures. Calderas are the collapsed depressions.
Their explosive nature suggests that there is a sizable magma chamber nearby.

Flood Basalt Provinces

Long-flowing, extremely fluid lava flows from these volcanoes.
India’s Deccan Traps are a much larger province of flood basalt that currently occupies most of the Maharashtra’s plateau.

Mid-Ocean Ridge Volcanoes

These volcanoes are located near oceans.
Entire ocean basins are traversed by a network of mid-ocean ridges, spanning over 70,000 km.
Eruptions occur frequently on the central section of this ridge.

Volcanic Landforms

When lava from volcanic eruptions cools, it condenses into igneous rocks.
Either from the inside or upon reaching the surface, the cooling process may occur.

Depending on where the lava cools down, volcanic landforms are created as a result of volcanic eruptions.

Intrusive Volcanic Landforms:

Batholiths

Inside the magma chamber, it is cooled magma.
In the deeper layers of the crust, this massive magma cools and takes the shape of a large dome.
It manifests on the surface of the earth following the denudation process.
It makes up the high mountain’s core.
A large area of upland is typically formed by granite.

Lacoliths

It is connected by a conduit or pipe channel from below and has a sizable dome shape with a level base.
Though it is above Batholiths, it is present at a deeper depth.
This portion of the Batholiths is exposed.
An illustration of this type of volcanic landform is the Karnataka hill.

Lopoliths:

It is wavy intrusive rocks parallel to the bedding plane.
It is found at the base of the syncline or the top of the anticline in folded igneous rocks.
It is found in lens shape.

Sills and Sheets:

Sills are the horizontal bodies of intrusive igneous rocks that remain after solidification and are caused by some lava moving in a horizontal direction.
Thinner deposits are referred to as sheets, and thicker deposits are called sills.
They are closer to the surface of the earth than they are at depth.

Dikes:

Lava travels through all potential directions in fissures and cracks during a volcanic eruption.
Dykes are wall-like formations created when magma cools in fissures and cracks.
Perpendicular to the crust of the earth, dykes are primarily located in western Maharashtra.
Lava erupting from these feeders creates decca cannels.

Extrusive Volcanic Landforms:

Cinder Cones:

It is low in height and composed of pyroclastic materials such as lava.
Gravity causes it to pile up in big no.
Its sides are straight and steep, and at the top is a crater.

Conical Vent:

a small, cylindrical opening that allows magma to burst during an explosion.
Volcanoes of the composite type are home to it.

Fissure Vent:

Similar to a conical vent, a small, linear vent releases magma without an explosion.
Shield-type volcanoes frequently experience it.
when a shield volcano—a massive mountain formed by the accumulation of basaltic lava flow in the area—occurs. Formerly Mauna Lao

Composite-type Volcanic Landforms:

Because of their pyroclastic and lava layers, these conical-shaped landforms are also referred to as stratovolcanoes.
Lava spews out in this formation along with a large amount of ash and pyroclastic debris. Andesitic lava predominates.
Examples are Mount Vesuvius and Mount Fiji.

Caldera:

When magma erupts from the earth’s surface, it creates an empty chambers inside the earth’s interior. Occasionally, external material disintegrates into the volcanic chamber, creating a caldera, which is shaped like a tube.
This becomes a caldera lake when rain or snowmelts into it.

Crater:

A crater is a vent that allows magma to escape during an eruption.
When it is dormant, it resembles an inverted cone and takes the form of a depression in the shape of a bowl.
A crater lake is created when snowmelts or rainwater collects. The world’s largest crater lake is called Lake Toba.

Flood Basalt:

It is large volume outpourings of basaltic magma from fissure vents.
It spread in large areas and builds up plateaus.

Hotspot Volcanism

A form of volcanism known as hotspot volcanism usually takes place inside the lithospheric plates as opposed to at the plate margins, or the point of areas of convergence and divergence.
The two hotspots at the divergent boundary, Iceland and Afar, are the exceptions.
The so-called anomalous volcanism, which can be found in Iceland or in excess along mid-ocean ridges in Iceland, or far from plate boundaries like in Hawaii and Yellowstone, is explained by hotspot volcanism.
The Hawaiian Hotspot, Yellowstone Hotspot, and Reunion Hotspot are a few well-known hotspots.
Mantle plumes, or unusually hot centers in the mantle, are the cause of hotspot volcanism.

Two primary theories that make an effort to explain their beginnings are as follows:-

The Mantle-Plume Theory: According to this theory, hot spots are caused by a permanent column of molten rock that is upwelling and coming from the asthenosphere, which is part of the Earth’s mantle.

Volcanic activity is produced when tectonic plates shift over this stationary plume, causing magma to rise through the Earth’s crust.

Additionally, the tectonic plate above may melt or become weaker due to the plume, causing the crust in the hot spot region to thin.

Follinger’s theory: also known as the Plate Weakness Theory, According to this theory, which was put forth by G. Foulger in 2003, hot spots can also be explained by tectonic plate weaknesses rather than just being connected to fixed mantle plumes.

This theory states that weak spots or “scars” on tectonic plates are the result of previous collisions, divergence, or additional geological events.

Volcanic activity can happen when sections of the crust of the earth with these pre-existing flaws cross over areas that contain subducted material that can melt at lower pressures.

Landforms Associated with Hotspots

Volcanic Islands:

When tectonic plates shift over the immobile mantle plume, these frequently result in chains of volcanic islands.
These islands can be shield volcanoes, stratovolcanoes, or cinder cone volcanoes, among other shapes.
The Canary Islands, Hawaii, and the Galápagos Islands are a few examples.

Large Igneous Provinces (LIPs)

Broad areas of intense volcanic eruptions are produced by certain hotspots, giving rise to sizable igneous provinces.
Large-scale strata of basaltic or others volcanic rock define LIPs.
LIPs include the Columbia River Basalt Group in the US Pacific Northwest and the Deccan Traps in India.

Rift Zones:

Rift zones are regions of tectonic extension and volcanic activity that are produced by hotspots.
Long fissures, broad lava flows, and occasionally even the creation of entirely new ocean basins can result from these zones.
One example of a rift zone is the East African Rift, which is connected to a hotspot.

Distribution of Earthquakes & Volcanoes across the World

The distribution of earthquakes and volcanoes around the world is extremely similar. Though they have the capacity to occur anywhere at any time, earthquakes generally follow three main zones on Earth. About seventy percent of earthquakes happen in the circum-Pacific region. About 20% are found in the Mediteranean-Himalayan belt, which includes parts of Northwest China, Asia Minor, and the Himalayas. Earth tremors can occur elsewhere on Earth’s crust, where it is less likely but still susceptible to them.

Circum-Pacific Seismic Belt: Approximately 81% of the world’s largest earthquakes occur in this seismic belt, which runs along the edge of the Pacific Ocean. The belt created by oceanic crust subducting along tectonic plate borders is referred to as the “Ring of Fire.” These subduction zones experience earthquakes as a result of plate rifts and slippage between plates.

Mid Continental Belt: The Alpine earthquake belt, which spans the Himalayas, the Mediterranean, and the Atlantic, extends from Europe to Sumatra. Approximately 17% of the biggest earthquakes in the world, which include some of the world’s most catastrophic ones, are located in this belt.

Mid-Atlantic Ridge: Submerged mid-Atlantic Ridge is followed by the third prominent belt. The divergent plate boundary known as the mid-Atlantic Ridge is located far from human development and is primarily under water.

India is located in the most seismically destructive earthquake belt, the Alpine earthquake belt.

The Mid-Atlantic belt’s volcanoes

The volcanic mountain range known as the Mid-Atlantic Ridge (MAR), or Mid-Atlantic Belt, stretches over 16,000 kilo meters from the Arctic up to the Antarctic

Similar to most other volcanic structures worldwide, the Mid-Atlantic Ridge is underwater; approximately 90% of the Mid-Atlantic Belt’s volcanic mountain ranges are submerged, with a depth of about 2500 meters.

Originally found in the nineteenth century, the range formerly encompassed both hemispheres. The Mid-Atlantic Ridge’s axial is visible in Iceland, but ninety percent of the range of mountains is underwater.

Circum Pacific Ring of Fire

The Pacific Ring of Fire is made up of numerous smaller volcanic structures, which is one of its most fascinating features. The belt’s volcanoes are dispersed individually, and eruptions and explosions take place at various times and places.

The following are some important details regarding the Pacific Ring of Fire:-

An estimated 850–1000 volcanoes that were active for the previous 11,700 years are thought to make up the Circum-Pacific region.
Within the Pacific Ring of Fire’s volcanic ranges happened the fourth-largest explosion in history.
The Circum-Pacific volcanic belt contains over 350 fully active volcanoes that date back to ancient times.
But the Pacific belt also contains ranges of dormant volcanoes that haven’t erupted in a millennium.

The following are a few of the Pacific Ring of Fire’s most well-known volcanoes:-

Volcano Agung is currently active.
The active volcano Sinabung
The active volcano Dukono

Geysers & Hot Springs

Hot springs known as geysers are defined by the erratic release of steam and geothermally heated water that is pushed from the earth’s surface with great force. On the contrary, hot springs are naturally occurring water bodies that have been heated by geothermal forces on the surface of the earth.

Despite their many similarities, geysers and hot springs differ only in that geysers eject water from the earth’s surface with tremendous force, whereas hot springs are merely naturally occurring water bodies that are heated by geothermal forces.

The US, the Russian Federation, Chile, New Zealand, and Iceland are the only five countries on Earth where geysers can be found. They are extremely uncommon geological formations. Conversely, hot springs are a fairly common geological formation that are primarily found near active volcanoes.

Hot springs are also more commonly known as hydrothermal springs and geothermal springs. These structures hold geothermally heated water present in craters on the earth’s surface. The water in the hot springs gets heated due to interacting with the hot mantle present below the earth’s crust.

The water in the hot springs is rich in minerals and iron with the presence of silica, carbon dioxide and carbonate minerals. People generally are attracted to the hot springs for relaxation and therapeutic purposes.