Mountain formation

Mountain formation

Mountain formation refers to the geological processes that underlie the formation of mountains. These processes are associated with large-scale movements of the earth's crust (plate tectonics).

Thrust and reverse fault movement are an important component of mountain formation.

Mountain formation is related to plate tectonics. Folding, faulting, volcanic activity, igneous intrusion and metamorphism are all parts of the organic process of mountain building.

The understanding of specific landscape features in terms of the underlying tectonic processes is called TECTONIC GEOMORPHOLOGY.

The study of geologically young or ongoing processes is called NEOTECTONICS.

Types of mountains

There are three main types of mountains:

1. volcanic,

2. fold, and

3. block

Volcano

A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface.

Movements of tectonic plates create volcanoes along the plate boundaries which erupt and form mountains. A volcanic arc system is a series of volcanoes that form near a subduction zone where the crust of a sinking oceanic plate melts.

Most volcanoes occur in a band encircling the Pacific Ocean (the Pacific Ring of Fire), and in another that extends from the Mediterranean across Asia to join the Pacific band in the Indonesian Archipelago.

Pacific Ring of Fire

The Ring of Fire has 452 volcanoes and is home to over 75% of the world's active and dormant volcanoes. It is sometimes called the circum-Pacific belt or the circum-Pacific seismic belt.

About 90% of the world's earthquakes and 81%[3] of the world's largest earthquakes occur along the Ring of Fire. The next most seismic region (5–6% of earthquakes and 17% of the world's largest earthquakes) is the Alpide belt, which extends from Java to Sumatra through the Himalayas, the Mediterranean, and out into the Atlantic. The Mid-Atlantic Ridge is the third most prominent earthquake belt

Types of Volcanic Mountain

Stratovolcano

Shield Volcano

Guyot

Stratovolcano

also known as a composite volcano, is a tall, conical volcano built up by many layers (strata) of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions and quiet eruptions. The lava

that flows from stratovolcanoes typically cools and hardens before spreading far due to high viscosity.

Mount Fuji, an active stratovolcano in Japan that last erupted in 1707–08

Stratovolcano scheme

1. Magma chamber2. Bedrock3. Conduit (pipe)4. Base5. Sill6. Branch pipe7. Layers of ash emitted by the volcano8. Flank9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater

15. Ash cloud

Shield volcano

a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes. This results in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form. Shield volcanoes contain low viscosity magma making it have flowing mafic lava.

Shield Volcano Scheme

1. Ash plume2. Lava fountain3. Crater4. . Lava lake5. Fumaroles 6. Lava flow7. Layers of lava and ash8. Stratum9. Sill10. Magma conduit 11. Magma chamber 12. Dike

Guyot

also known as a tablemount, is an isolated underwater volcanic mountain (seamount), with a flat top over 200 meters (660 feet) below the surface of the sea. The diameters of these flat summits can exceed 10 km (6.2 mi).

Guyots are most commonly found in the Pacific Ocean.

There are thought to be an estimated 2,000 seamounts in the Pacific basin.

Erupted Material

Material erupted by a volcano is called as lava. Lava is just a name given to magma, once it gets erupted from the mouth of volcano.Now this magma can be classified into 4 types-

1. Magma containing large amounts (>63%) of silica. This type of lava is called as felsic.2. Magma having 52–63% of silica.3. Magma having 45-52% of silica. It is called mafic, because of high composition of iron and magnesium.4. Magma having <=45% of silica.

Effects of Volcanic Eruptions

Different volcanic eruptions produce different sort of effects on environment and society. General eruption contains gases like water vapors, SO2, HF, CO2, HCl and ashes of melted rocks. Explosive eruptions supply these materials directly to the stratosphere at the heights of 16–32 kms. Now in stratosphere SO2 gets converted into H2SO4, this H2SO4 gets condensed into the sulfate aerosols. Accumulation of sulfate aerosols in earth’s atmosphere increases its reflection for the rays of sun; as a result temperature gets decreased in lower layer of atmosphere called troposphere, but due to accumulation of aerosols in stratosphere, temperature gets increased here. This temperature cuts and fluctuations produce large effects on overall earth’s temperature. Accumulation of sulfate aerosols also causes chemical reactions which eventually cause destruction of protective ozone layer of earth’s atmosphere. Acid rain is also a common effect of volcanic eruptions. Moreover when a volcanic eruptions occurs the flow of lava destroy all the surrounding crops of the region and people need to migrate from that zone because flow of lava destroy each and each every thing coming on its way. Ash and rain of molten rocks are other effects of volcanic eruptions.

Popular classification of volcanoes

A popular way of classifying magmatic volcanoes is by their frequency of eruption, with those that erupt regularly called active, those that have erupted in historical times but are now quiet called dormant or inactive, and those that have not erupted in historical times called extinct. However, these popular classifications—extinct in particular—are practically meaningless to scientists.

Active

There is no consensus among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes meaningless when compared to the lifespans of humans or even civilizations. For example, many of Earth's volcanoes have erupted dozens of times in the past few thousand years but are not currently showing signs of eruption. Given the long lifespan of such volcanoes, they are very active. By human lifespans, however, they are not.

Extinct

Extinct volcanoes are those that scientists consider unlikely to erupt again, because the volcano no longer has a magma supply. Examples of extinct volcanoes are many volcanoes on the Hawaiian – Emperor Seamount chain in the Pacific Ocean, Hohentwiel, Shiprock and the Zuidwal volcano in theNetherlands. Edinburgh Castle in Scotland is famously located atop an extinct volcano. Otherwise, whether a volcano is truly extinct is often difficult to determine.

Dormant

It is difficult to distinguish an extinct volcano from a dormant (inactive) one. Volcanoes are often considered to be extinct if there are no written records of its activity. Nevertheless, volcanoes may remain dormant for a long period of time. For example, Yellowstone has a repose/recharge period of around 700 ka, and Toba of around 380 ka.[7] Vesuvius was described by Roman writers as having been covered with gardens and vineyards before its famous eruption of AD 79, which destroyed the towns of Herculaneum and Pompeii. Before its catastrophic eruption of

1991, Pinatubo was an inconspicuous volcano, unknown to most people in the surrounding areas

Traditional beliefs about volcanoes

Many ancient accounts ascribe volcanic eruptions to supernatural causes, such as the actions of gods or demigods. To the ancient Greeks, volcanoes' capricious power could only be explained as acts of the gods, while 16th/17th-century German astronomer Johannes Kepler believed they were ducts for the Earth's tears.[26] One early idea counter to this was proposed by Jesuit Athanasius Kircher (1602–1680), who witnessed eruptions of Mount Etna and Stromboli, then visited the crater of Vesuvius and published his view of an Earth with a central fire connected to numerous others caused by the burning of sulfur, bitumen and coal.

Various explanations were proposed for volcano behavior before the modern understanding of the Earth's mantle structure as a semisolid material was developed. For decades after awareness that compression and radioactive materials may be heat sources, their contributions were specifically discounted. Volcanic action was often attributed to chemical reactions and a thin layer of molten rock near the surface.

Fold Mountains

When plates collide or undergo subduction (that is ride one over another), the plates tend to buckle and fold, forming mountains. Most of the major continental mountain ranges are associated with thrusting and folding or orogenesis. Examples are the Jura and the Zagros mountains.

Block Mountains

When a fault block is raised or tilted, Block Mountains can result. Higher blocks are called horsts and troughs are called grabens. A spreading apart of the surface causes tensional forces. When the tensional forces are strong enough to cause a plate to split apart, it will do so such that a center block will drop down relative to its flanking blocks.