Geography

Earthquakes and Volcanoes

By Examguru / 06 Oct, 2023 / Download PDF

Earthquakes and Volcanoes

Earthquakes

  • The sudden tremors or shaking of the earth's crust is called an earthquake. When a part of the earth's surface moves backward and forward or up and down, the earth's surface 'quakes', and these are called the 'earthquake'.
  • The earth's crust is made up of different parts of various sizes. They are called plates. Most of the earthquakes in the world are caused by the movements of the plates (Tectonism),
  • 'Seismology' the special branch of Geology, It deals with the study of earthquake.
  • 'Richter scale' and 'Mercalli scale' are the instruments to measure/record the magnitude and the intensity of an earthquake respectively.

Seismic Waves

  • The place where the seismic waves originate beneath the earth's surface is called the focus of the earthquake.
  • The epicenter is that point on the ground surface which is closest to the focus.
  • Seismic waves are recorded on the seismograph Seismic waves are mainly of three types-1. Primary waves, 2 Secondary waves and 3. Surface or Long waves.

NASA launched first ever INSIGHT (Interior Exploration using Seismic Investigation, Geodesy and Heat Transport) Mission (on 5 May, 2018) to explore the deep interior of Mars. It was launched by United Launch Alliance (ULA) Atlas V rocket from space launch complex 2 at Vandenberg Air force Base in California.

The earthquake zones in India

  • The Indian plate is moving from south to north. That is why there are earthquakes in the Himalayan region.
  • Earthquakes occur in Assam, Arunachal Pradesh, Nagaland, Tripura, Manipur, Mizoram, Andaman and Nicobar Islands, Jammu and Kashmir, the northwestern region of Uttar Pradesh, the northern region of Bihar etc.
  • During the last few years, there have been several earthquakes of varying intensities in Maharashtra and Gujarat.

Volcanic Activity

  • Magma or molten rock is formed beneath the ground surface due to various reasons.
  • This molten rock ruptures the ground and pours out Sometimes, it cools down beneath the ground surface instead of pouring out.
  • All these activities are called volcanic activities.
  • Volcanic activities have been taking place since times immemorial.

There are three types of Volcanoes:

1. Active Volcanoes 2. Dormant Volcanoes 3. Extinct Volcanoes.

1. Active Volcanoes:

These volcanoes constantly eject volcanic lavas, gases, ashes and fragmental materials. It is estimated that there are more than 500 active volcanoes in the world. Etna and Strombol are the most significant examples of this category. Stromboli is known as the Light house of the Mediterranean. Other volcanoes of this category are - Cotopaxi of Ecuador (World's highest active volcano), Mt. Erebus of Antarctica (the only active volcano of the continent) and the active volcano in the Barren Island of the Andaman and Nicobar Islands, India.

2. Dormant Volcanoes:

These volcanoes become quiet after their eruptions for some time and there is no indication for future eruptions but suddenly they erupt very violently and cause enormous damage to human health and wealth. Important examples of this category are Vesuvius (Italy), Fujiyama (Japan) Krakatao (Indonesia) and Dormant volcanoes in the Narcondam Island, now believed to be active after Tsunami of December 2004, (Andaman & Nicobar).

3. Dead or Extinct Volcanoes:

These are those volcanoes which have not erupted since thousands of years and there is no indication of future eruption as well. Main examples of this category are - Mt. Kenya and Mt. Kilimanjaro (Eastern part of Africa), Chimborazo (Ecuador), Popa (Myanmar), Damavand (Iran) and Koh-i-Sultan (Pakistan) and Aconcagua in Andes mountains.

Volcanic Eruptions

  • The pouring out of the magma or molten rock through ground surface is called a volcanic eruption.
  • At the time of eruption, the magma, steam, fragments of rock, dust and gaseous substances are ejected with great force from under the ground surface through a pipe like passage.
  • The opening of this pipe on the earth's surface is known as the vent which forms a crater.
  • The lava which is thrown into the sky during an eruption, falls to the ground in the form of solid fragments. Dark clouds gather in the sky and it begins to rain heavily.
  • The volcanic ash and dust mixes with the rainwater giving rise to hot mud flows.

Types of Volcanic Eruptions

  • Volcanic eruptions are classified into two types depending on the manner of ejection of the magma

1. Central eruption, 2. Fissure eruption.

Central Eruption

  • This type of eruption gives rise to conical or domeshaped hills. Some examples of volcanic mountains formed due to central eruption are Mt. Kilimanjaro in Africa, the Fujiyama in Japan and the Vesuvius and Mount Etna in Italy.
  • It is basically poured acidic lava.

Fissure Eruption

  • These eruptions take place at a very slow speed. Since this lava is more fluid, it spreads over longer distances.
  • The lava cools down on the ground over a period of time, increasing the thickness of the surface in that area Basalt plateaus are formed due to these eruptions.
  • Basalt plateaus are also found in Brazil in South America and Saudi Arabia in West Asia and Deccan plateau in India.
  • In Maharashtra, the fertile black regur soil has beer formed from basalt rocks. It is also called black cotton soil.

The opening of exploded volcano is of different types Some important types are—

Crater this is funnel or cup-shaped opening at the top of the volcanic cone. It gets filled up with rain water then it forms a crater lake, e.g.- Loner Lake in Buldhana district (Maharashtra). Sometimes many small craters are formed in a single crater. This take place when the exposition was of less intensity than that of pre-existing crater, these are known as Nested craters, e.g. the three small craters of Mountain (Philippines).

Caldera this is widened form of crater which is formed due to depression of the crater or expansion of volcanic mouth or vent due to successive eruptions. Depending on their intensity and duration, volcanic eruptions can create calderas as much as 100 km (62 miles) wide. Mt. Aso of Japan is an example of Caldera. The Toba Caldera on the Indonesian island of Sumatra is the newest resurgent caldera.

 

World Distribution of Volcanoes

The explanation of volcanic regions of the world, rased on the Plate tectonic theory, is the most accepted one. According to this theory destructive plate boundaries account for about 80% of the volcanic regions, constructive plate margins for about 15% of the volcanic regions and remaining are in the interior parts of the plates which are not yet explained by the Plate tectonic theory.

Major Volcanoes of the World

S.

Volcano

Country

1

Ojos del Salado

Argentina-Chile

2

Cotopaxi

Ecuador

3

Chimborazo

Ecuador

4

Popocaepetl

Mexico

5

Mauna Loa

Hawaii Island

6

Mt. Cameroon

Cameroon (Central Africa)

7

Mt. Erebus

Ross Island (Antarctica)

8

Mt. Etna

Sisily (Italy)

9

Mt. Pelee

Martinique Island (France)

10

Hekla

Iceland

11

Mt. Vesuvius

Gulf of Neples, Compnia (Italy)

12

Stromboli

Stromboli Island, Sisily (Italy)

13

Krakatoa

Indonesia

14

Mt. Katmai

Alaska (US)

15

Mt. Rainier

Washington (US)

16

Mt. Shasta

California (US)

17

Mt. FujiorFuji-San(Fujiyama)

Japan

18

Taal

Luzon Island, Philippines

19

Mt. Pinatubo

Philippines

20

Mt. Mayon

Luzon Island, Philippines

21

Damavand

Iran

22

Koh-i-Sultan

Balochistan (Pakistan)

23

Mt. Popa or Popa Hill

Myanmar

24

Mt. Elbrus

Russia

25

Kilimanjaro

Tanzania

26

Mt. Kenya

Kenya

More Related Articles

Introduction - Geography

The word Geography was first used by a Greek scholar Eratosthenes (276-194 B.C.). The word Geography has been derived from two Greek words- Geo and Graphos, which jointly means the description

examguru by ExamGuru

The Solar System & Universe

Universe The universe is commonly defined as the totality of everything that exists, including all physical matter and energy, the planets, stars, galaxies and the contents of intergalactic

examguru by ExamGuru

Continents of the World

Asia, Africa, North America, South America, Europe, Australia and Antarctica are the seven continents. Asia: The word 'Asia' is derived from the word 'Asu' (of Hibru language), w

examguru by ExamGuru

Oceans on The Earth

There are four oceans. In order of their size, they are: Pacific Ocean, Atlantic Ocean, Indian Ocean and Arctic Ocean. Pacific Ocean The explorer Ferdinand Magellan, who circumnaviga

examguru by ExamGuru

Biosphere: Lithosphere, Hydrospher

Biosphere The part of the Earth where life exists is called the Biosphere ('bios'means 'life'). The Earth is the only planet of the solar system that supports life. Life is pos

examguru by ExamGuru

Time & Zones (Latitude and Longitude)

Latitude and Longitude Any location on Earth is described by two numbers- its latitude and its longitude. Latitude On a globe of the Earth, lines of latitude are circles of different siz

examguru by ExamGuru

Coriolis & Different Effect

Coriolis Force The invisible force that appears to deflect the wind is the Coriolis force. The Coriolis force applies to movement on rotating objects. It is determined by the mass of the object

examguru by ExamGuru

Atmosphere

The envelope of air that completely surrounds the earth is known as atmosphere. The atmosphere extends to about 1000 km from the surface of the earth. But 99% of the total mass of the atmosphere

examguru by ExamGuru

Winds, Clouds, Rainfall, Islands & Rocks

Winds Wind is the movement of air caused by the uneven heating of the Earth by the Sun. Sometimes wind blows gently, refreshing us. At other times, it blows strongly creating storms th

examguru by ExamGuru

Various Landforms – Mountains, Plateaus, Plains, Glaciers, Rivers, Groundwater etc. / India Physical Features

Mainly there are three types of landforms - Mountains, Plateaus, Plains. Mountains The height of mountains is over 600 m and haveconical peaks. On the basis of origin there are four types of

examguru by ExamGuru

Toppers

anil kumar
Akshay kuamr
geeta kumari
shubham