Earthquakes And Volcanoes

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: Types, distribution and their impact:-

Earthquake:-

The study of seismic waves provides a complete picture of the layered interior. An earthquake in simple words is shaking of the earth. It is a natural event. It is caused due to release of energy, which generates waves that travel in all directions.

Why does the earth shake?

The release of energy occurs along a fault. A fault is a sharp break in the crustal rocks. Rocks along a fault tend to move in opposite directions. As the overlying rock strata press them, the friction locks them together. However, their tendency to move apart at some point of time overcomes the friction. As a result, the blocks get deformed and eventually, they slide past one another abruptly. This causes a release of energy, and the energy waves travel in all directions. The point where the energy is released is called the focus of an earthquake, alternatively, it is called the hypocentre. The energy waves  travelling in different directions reach the surface. The point on the surface, nearest to the focus, is called epicentre. It is the first one to experience the waves. It is a point directly above the focus.

Earthquake Waves:-

All natural Earthquakes take place in the lithosphere. It is sufficient to note here that the lithosphere refers to the portion of depth up to 200 km from the surface of the earth. An instrument called ‘seismograph’ records the waves reaching the surface.

Earthquake waves are basically of two types — body waves and surface  waves. Body waves are generated due to the release of energy at the focus and move in all directions travelling through the body of the earth.  The body waves interact with the surface rocks and generate new set of waves called Surface Waves. These waves move along the surface. The velocity of waves changes as they travel through materials with different densities. The denser the material, the higher is the velocity. Their direction also changes as they reflect or refract when coming across materials with different densities. There are two types of body waves. They are called P and S-waves. P-waves  move faster and are the first to arrive at the surface. These are also called ‘primary waves’. The P-waves are similar to Sound waves. They travel through gaseous, liquid and solid materials. S-waves arrive at the surface with some time lag. These are called secondary waves. An important fact about S-waves is that they can travel only through solid materials. This characteristic of the S-waves is quite important. It has helped scientists to understand the structure of the Interior Of The Earth. Reflection causes waves to rebound whereas refraction makes waves move in different directions. The variations in the direction of waves are inferred with the help of their record on  seismograph. The surface waves are the last to report on seismograph. These waves are more destructive. They cause displacement of rocks, and hence, the collapse of structures occurs.

Propagation of Earthquake Waves:-

Different types of earthquake waves travel in different manners. As they move  or propagate, they cause vibration in the body of the rocks through which they pass. P-waves vibrate parallel to the direction of the wave. This exerts pressure on the material in the direction of the propagation. As a result, it creates density differences in the material leading to stretching and squeezing of the material. Other three waves vibrate perpendicular to the direction of propagation. The direction of vibrations of S-waves is perpendicular to the wave direction in the vertical plane. Hence, they create troughs and crests in the material through which they pass. Surface waves are considered to be  the most damaging waves.

Emergence of Shadow Zone:-

Earthquake waves get recorded in seismographs located at far off locations. However, there exist some specific areas where the waves are not reported. Such a zone is called the ‘shadow zone’. The study of different events reveals that for each earthquake, there exists an altogether different shadow zone.

 

Types of Earthquakes

(i) The most common ones are the tectonic earthquakes. These are generated due to sliding of rocks along a fault plane.

(ii) A special class of tectonic earthquake is sometimes recognised as volcanic earthquake. However, these are confined to areas of active Volcanoes-2/”>Volcanoes.

(iii) In the areas of intense mining activity, sometimes the roofs of underground mines collapse causing minor tremors. These are called collapse earthquakes.

(iv) Ground shaking may also occur due to the explosion of chemical or nuclear devices. Such tremors are called explosion earthquakes.

Effects of Earthquake

Earthquake is a NATURAL HAZARD. The following are the immediate hazardous effects of earthquake:

(i) Ground Shaking

(ii) Differential ground settlement

(iii) Land and mud slides

(iv) Soil liquefaction

(v) Ground lurching

(vi) Avalanches

(vii) Ground displacement

(viii) Floods from dam and levee failures

(ix) Fires

(x) Structural collapse

(xi) Falling objects

(xii) Tsunami

 

Volcanoes:-

Volcanoes are classified on the basis of nature of eruption and the form developed at the surface. Major Types of Volcanoes are as follows:

Shield Volcanoes:-

Barring the basalt flows, the shield volcanoes are the largest of all the volcanoes on the earth. The Hawaiian volcanoes are the most famous examples. These volcanoes are mostly made up of basalt, a type of lava that is very fluid when erupted. For this reason, these volcanoes are not steep. They become explosive if somehow water gets into the vent; otherwise, they are characterised by low-explosivity. The upcoming lava moves in the form of a fountain and throws out the cone at the top of the vent and develops into cinder cone.

Composite Volcanoes

These volcanoes are characterised by eruptions of cooler and more viscous lavas than basalt. These volcanoes often result in explosive eruptions. Along with lava, large quantities of pyroclastic material and ashes find their way to the ground. This material accumulates in the vicinity of the vent openings leading to formation of layers, and this makes the mounts appear as composite volcanoes.

Caldera

These are the most explosive of the earth’s volcanoes. They are usually so explosive that when they erupt they tend to collapse on themselves rather than building any tall structure. The collapsed depressions are called calderas. Their explosiveness indicates that the magma chamber supplying the lava is not only huge but is also in close vicinity. Flood Basalt Provinces. These volcanoes outpour highly fluid lava that flows for long distances. Some parts of the world are covered by thousands of sq. km of thick basalt lava flows. There can be a series of flows with some flows attaining thickness of for hundreds of km. The Deccan Traps from India, presently covering most of the Maharashtra plateau, are a much larger flood basalt province. It is believed that initially the trap formations covered a much larger area than the present.

Mid-Ocean Ridge Volcanoes

These volcanoes occur in the oceanic areas. There is a system of mid-ocean ridges more than 70,000 km long that stretches through all the ocean basins. The central portion of this ridge experiences frequent eruptions.

VOLCANIC Landforms

Intrusive Forms

The lava that is released during volcanic eruptions on cooling develops into Igneous Rocks. The cooling may take place either on reaching the surface or also while the lava is still in the crustal portion. Depending on the location of the cooling of the lava, igneous rocks are classified as volcanic rocks cooling at the surface) and plutonic rocks (cooling in the crust). The lava that cools within the crustal portions assumes different forms. These forms are called intrusive forms.

Batholiths

A large body of magmatic material that cools in the deeper depth of the crust develops in the form of large domes. They appear on the surface only after the Denudational Processes remove the overlying materials. They cover large areas, and at times, assume depth that may be several km. These are granitic bodies. Batholiths are the cooled portion of magma chambers.

Lacoliths

These are large dome-shaped intrusive bodies with a level base and connected by a pipe-like conduit from below. It resembles the surface volcanic domes of composite volcano, only these are located at deeper depths. It can be regarded as the localised source of lava that finds its way to the surface. The Karnataka plateau is spotted with domal hills of granite rocks. Most of these, now exfoliated, are examples of lacoliths or batholiths. Lapolith, Phacolith and Sills As and when the lava moves upwards, a portion of the same may tend to move in a horizontal direction wherever it finds a weak plane. It may get rested in different forms. In case it develops into a saucer shape, concave to the sky body, it is called lapolith. A wavy mass of intrusive rocks, at times, is found at the base of synclines or at the top of anticline in folded igneous country. Such wavy materials have a definite conduit to source beneath in the form of magma chambers (subsequently developed as batholiths). These are called the phacoliths.  The near horizontal bodies of the intrusive igneous rocks are called sill or sheet, depending on the thickness of the material. The thinner ones are called sheets while the thick horizontal deposits are called sills.

Dykes

When the lava makes its way through cracks and the fissures developed in the land, it solidifies almost perpendicular to the ground. It gets cooled in the same position to develop a wall-like structure. Such structures are called dykes. These are the most commonly found intrusive forms in the western Maharashtra area. These are considered the feeders for the eruptions that led to the development of the Deccan traps.



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Earthquakes and volcanoes are two of the most powerful forces on Earth. They can cause widespread destruction and loss of life, but they also play an important role in shaping the planet’s surface.

Earthquakes

An earthquake is the shaking of the ground caused by a sudden release of energy in the Earth’s crust. The energy released by an earthquake can travel through the Earth’s crust in waves, causing the ground to shake.

The most common cause of earthquakes is the movement of tectonic plates. Tectonic plates are large pieces of the Earth’s crust that float on the molten rock below. When these plates move, they can grind against each other or collide. This friction can build up energy, which is released when the plates suddenly move.

Other causes of earthquakes include volcanic eruptions, landslides, and nuclear explosions.

There are three main types of earthquakes: tectonic, volcanic, and induced. Tectonic earthquakes are the most common type and are caused by the movement of tectonic plates. Volcanic earthquakes are caused by the movement of magma beneath a volcano. Induced earthquakes are caused by human activity, such as the construction of Dams or mining.

The strength of an earthquake is measured on the Richter magnitude scale. The Richter magnitude scale is a logarithmic scale, which means that each whole number increase on the scale represents a tenfold increase in the earthquake’s energy. For example, an earthquake with a magnitude of 6 is ten times more powerful than an earthquake with a magnitude of 5.

The effects of an earthquake can be devastating. Earthquakes can cause buildings to collapse, roads to buckle, and bridges to fall. They can also trigger landslides and Tsunamis. Earthquakes can also cause injuries and deaths.

There are a number of things that can be done to reduce the risk of earthquake damage. These include building earthquake-resistant structures, installing early warning systems, and developing evacuation plans.

Volcanoes

A volcano is an opening in the Earth’s crust through which molten rock, ash, and gases erupt. Volcanoes are formed when magma rises to the surface through cracks or fissures in the crust.

The magma that erupts from a volcano is made up of molten rock, gas, and crystals. The molten rock is called lava. The gas is mostly water vapor, but it also contains other gases such as carbon dioxide, sulfur dioxide, and hydrogen sulfide. The crystals are made of Minerals such as olivine, pyroxene, and feldspar.

There are three main types of volcanoes: shield volcanoes, stratovolcanoes, and cinder cones. Shield volcanoes are the most common type of volcano. They are formed by the eruption of low-viscosity lava that flows long distances. Stratovolcanoes are tall, conical volcanoes that are formed by the eruption of high-viscosity lava. Cinder cones are small, steep-sided volcanoes that are formed by the eruption of cinders and ash.

Volcanoes can be active, dormant, or extinct. Active Volcanoes are volcanoes that have erupted in the past 10,000 years. Dormant Volcanoes are volcanoes that have not erupted in the past 10,000 years, but are still considered to be a threat. Extinct Volcanoes are volcanoes that are not expected to erupt again.

The effects of a volcanic eruption can be devastating. Volcanic eruptions can cause ashfalls, lava flows, pyroclastic flows, and tsunamis. Ashfalls can cause respiratory problems, crop damage, and power outages. Lava flows can destroy buildings and Infrastructure-2/”>INFRASTRUCTURE. Pyroclastic flows are hot, fast-moving clouds of ash, gas, and rock that can travel at speeds of up to 700 kilometers per hour. Pyroclastic flows can incinerate everything in their path. Tsunamis are large waves that can be caused by volcanic eruptions, earthquakes, or landslides. Tsunamis can cause widespread damage and loss of life.

There are a number of things that can be done to reduce the risk of volcanic damage. These include building volcanic-resistant structures, installing early warning systems, and developing evacuation plans.

Conclusion

Earthquakes and volcanoes are two of the most powerful forces on Earth. They can cause widespread destruction and loss of life, but they also play an important role in shaping the planet’s surface. By understanding these natural hazards, we can take steps to reduce the risk of damage and loss of life.

1. What is the difference between an earthquake and a volcano?

An earthquake is the shaking of the ground caused by a sudden release of energy in the Earth’s crust. A volcano is an opening in the Earth’s surface through which lava, ash, and gases erupt.

2. What causes earthquakes?

Earthquakes are caused by the movement of tectonic plates, which are large pieces of the Earth’s crust that float on the Earth’s mantle. When these plates move, they can grind against each other or collide, causing the ground to shake.

3. What causes volcanoes?

Volcanoes are caused by the movement of magma, which is molten rock that lies beneath the Earth’s surface. Magma can rise to the surface through a volcano when it is pushed up by tectonic plates or when it is heated by the Earth’s core.

4. What are the effects of earthquakes?

The effects of earthquakes can vary depending on the magnitude of the earthquake and the distance from the epicenter. Earthquakes can cause damage to buildings, infrastructure, and natural features. They can also cause injuries and deaths.

5. What are the effects of volcanoes?

The effects of volcanoes can also vary depending on the size of the eruption and the distance from the volcano. Volcanic eruptions can release ash, lava, and gases into the Atmosphere. This can cause Air Pollution, Acid Rain, and Climate change. Volcanic eruptions can also cause damage to buildings, infrastructure, and natural features. They can also cause injuries and deaths.

6. How can earthquakes and volcanoes be prevented?

Earthquakes and volcanoes cannot be prevented, but their effects can be mitigated. Earthquake-resistant buildings and infrastructure can be built to reduce the damage caused by earthquakes. Volcanic eruptions can be monitored to predict when they are likely to occur. This allows people to evacuate the area and take precautions to protect themselves from the effects of the eruption.

7. What are some interesting facts about earthquakes and volcanoes?

  • The largest earthquake ever recorded was the 1960 Valdivia earthquake in Chile, which had a magnitude of 9.5.
  • The most active volcano in the world is KÄ«lauea in Hawaii, which has been erupting continuously since 1983.
  • The largest volcanic eruption in history was the Toba eruption in Indonesia, which occurred about 74,000 years ago and is estimated to have killed 60-70% of the human Population at the time.
  • Earthquakes and volcanoes can be beneficial to humans. Earthquakes can help to create new landforms, and volcanoes can provide us with valuable Resources such as metals and minerals.

8. What are some safety tips for earthquakes and volcanoes?

  • If you are in an earthquake, stay calm and drop, cover, and hold on.
  • If you are in a building during an earthquake, get under a sturdy piece of furniture or against an interior wall.
  • If you are outside during an earthquake, move away from buildings and power lines.
  • If you are in a car during an earthquake, pull over to the side of the road and stop.
  • If you are near a volcano, stay away from the volcano and listen to the instructions of local officials.
  • If you are in an area that is prone to earthquakes or volcanoes, have a plan in place and make sure you have supplies such as food, water, and a first-aid kit.

Sure, here are some multiple choice questions about the topics of earthquakes and volcanoes:

  1. What is the most common type of earthquake?
    (A) Tectonic earthquakes
    (B) Volcanic earthquakes
    (C) Induced earthquakes
    (D) Seismic waves

  2. What is the Richter magnitude scale?
    (A) A scale that measures the energy released by an earthquake
    (B) A scale that measures the intensity of an earthquake
    (C) A scale that measures the depth of an earthquake
    (D) A scale that measures the frequency of earthquakes

  3. What is the Mercalli intensity scale?
    (A) A scale that measures the energy released by an earthquake
    (B) A scale that measures the intensity of an earthquake
    (C) A scale that measures the depth of an earthquake
    (D) A scale that measures the frequency of earthquakes

  4. What is the epicenter of an earthquake?
    (A) The point on the surface of the Earth directly above the focus of an earthquake
    (B) The point on the surface of the Earth directly below the focus of an earthquake
    (C) The point on the surface of the Earth where the earthquake is most intense
    (D) The point on the surface of the Earth where the earthquake first occurs

  5. What is the focus of an earthquake?
    (A) The point on the surface of the Earth directly above the epicenter of an earthquake
    (B) The point on the surface of the Earth directly below the epicenter of an earthquake
    (C) The point on the surface of the Earth where the earthquake is most intense
    (D) The point on the surface of the Earth where the earthquake first occurs

  6. What is a fault?
    (A) A break in the Earth’s crust along which movement has occurred
    (B) A crack in the Earth’s crust along which movement has not occurred
    (C) A fold in the Earth’s crust
    (D) A dome in the Earth’s crust

  7. What is a volcano?
    (A) A mountain formed by the eruption of molten rock, ash, and gas from the Earth’s interior
    (B) A crack in the Earth’s crust through which molten rock, ash, and gas erupt
    (C) A mountain formed by the accumulation of sediment
    (D) A mountain formed by the erosion of rock

  8. What is a lava flow?
    (A) A stream of molten rock that flows down the side of a volcano
    (B) A cloud of ash and gas that erupts from a volcano
    (C) A cloud of hot gas that erupts from a volcano
    (D) A cloud of steam that erupts from a volcano

  9. What is a pyroclastic flow?
    (A) A stream of molten rock that flows down the side of a volcano
    (B) A cloud of ash and gas that erupts from a volcano
    (C) A cloud of hot gas that erupts from a volcano
    (D) A cloud of steam that erupts from a volcano

  10. What is a tsunami?
    (A) A large wave caused by an earthquake or volcanic eruption
    (B) A small wave caused by a storm
    (C) A long wave caused by the wind
    (D) A short wave caused by the wind

I hope these questions were helpful!