Earthquakes and Volcanoes: Types, distribution and their impact

Earthquakes and Volcanoes-2/”>Volcanoes: 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.

(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.,

Earthquakes And Volcanoes are two of the most powerful and destructive natural forces on Earth. They can cause widespread damage and loss of life, and their effects can be felt for miles around.

Earthquakes are caused by the sudden release of energy along fault lines in the Earth’s crust. When two tectonic plates move past each other, they can grind together or stick together. If the plates stick together for too long, the Stress builds up until it is released in a sudden jolt, causing an earthquake.

There are three main types of earthquakes: tectonic earthquakes, volcanic earthquakes, and induced earthquakes. Tectonic earthquakes are the most common type, and they 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 oil and gas drilling.

Earthquakes can occur anywhere on Earth, but they are most common along tectonic plate boundaries. The most active earthquake zones are the Ring of Fire, which surrounds the Pacific Ocean, and the Alpide belt, which runs through Europe, Asia, and North Africa.

The impact of earthquakes can be devastating. Ground shaking can damage buildings and Infrastructure-2/”>INFRASTRUCTURE, and it can also cause landslides and liquefaction. Tsunamis, which are large waves caused by earthquakes, can also cause widespread damage.

Volcanoes are formed when magma, or molten rock, rises to the surface of the Earth. Magma can rise to the surface through cracks in the Earth’s crust, or it can erupt through a volcano.

There are four main types of volcanoes: shield volcanoes, cinder cones, composite volcanoes, and stratovolcanoes. Shield volcanoes are the most common type, and they are formed by the eruption of low-viscosity lava. Cinder cones are formed by the eruption of cinders, which are small pieces of volcanic rock. Composite volcanoes are the most destructive type, and they are formed by the eruption of both lava and pyroclastic material. Stratovolcanoes are similar to composite volcanoes, but they are larger and have a more complex structure.

Volcanoes are most common along tectonic plate boundaries. The Ring of Fire, which surrounds the Pacific Ocean, is the most active volcanic region on Earth.

The impact of volcanoes can be devastating. Lava flows can destroy buildings and infrastructure, and they can also cause fires. Pyroclastic flows, which are fast-moving clouds of hot gas and ash, can also cause widespread damage. Ashfalls can contaminate water supplies and make it difficult to breathe. Lahars, which are mudflows made up of volcanic ash, water, and rock, can also cause significant damage.

Earthquakes and volcanoes are both natural hazards that can cause widespread damage and loss of life. It is important to be aware of the risks posed by these hazards and to take steps to protect yourself and your property.

Here are some tips to stay safe during an earthquake:

• Drop, cover, and hold on. If you are indoors when an earthquake strikes, immediately drop to the ground, cover your head and neck with your arms, and hold on to something sturdy until the shaking stops.
• Stay away from windows and doors. Windows and doors can break during an earthquake, and flying glass can cause serious injuries.
• If you are in bed when an earthquake strikes, stay there and hold on until the shaking stops. Do not try to get out of bed, as you could be injured by falling objects.
• If you are outside when an earthquake strikes, move away from buildings, power lines, and trees. These objects can fall and injure you during an earthquake.

Here are some tips to stay safe during a volcanic eruption:

• If you live in an area that is at risk of volcanic eruption, it is important to have a plan in place. This plan should include evacuation routes, emergency supplies, and contact information for local authorities.
• If you are caught in a volcanic eruption, it is important to stay calm and follow the instructions of emergency personnel. Do not try to outrun the eruption, as it is much faster than you are.
• If you are caught in a pyroclastic flow, it is important to find shelter immediately. If you cannot find shelter, try to cover your mouth and nose with a cloth to protect yourself from the ash and gas.
• If you are caught in an ashfall, it is important to stay indoors and avoid breathing in the ash. If you must go outside, wear a mask or cloth over your mouth and nose.

Earthquakes and volcanoes are both powerful and destructive natural forces. However, by being aware of the risks and taking steps to protect yourself, you can reduce your chances of being injured or killed in an event.

What is an earthquake?

An earthquake is the shaking of the ground caused by a sudden release of energy in the Earth’s crust.

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 molten rock below. When these plates move, they can grind against each other or slide past each other. This friction can build up over time, and when it is released, it can cause an earthquake.

What are the different types of earthquakes?

There are two main types of earthquakes: tectonic earthquakes and volcanic earthquakes. Tectonic earthquakes are the most common type of earthquake, and they are caused by the movement of tectonic plates. Volcanic earthquakes are caused by the movement of magma beneath a volcano.

What are the different ways to measure earthquakes?

There are two main ways to measure earthquakes: the Richter magnitude scale and the Mercalli intensity scale. The Richter magnitude scale measures the size of an earthquake, while the Mercalli intensity scale measures the effects of an earthquake on the surface.

What are the effects of earthquakes?

Earthquakes can cause a variety of effects, including ground shaking, landslides, tsunamis, and fires. Ground shaking can damage buildings and other structures, and it can also cause injuries and deaths. Landslides can occur when the ground is shaken, and they can block roads and railways. Tsunamis are large waves that can be caused by earthquakes that occur near the coast. Tsunamis can cause extensive damage to coastal areas. Fires can be caused by earthquakes when power lines are knocked down or when gas lines are ruptured.

How can we protect ourselves from earthquakes?

There are a number of things that we can do to protect ourselves from earthquakes, including:

• Building our homes and other structures to withstand earthquakes
• Having a plan in place for what to do in the event of an earthquake
• Participating in earthquake drills
• Knowing the location of the nearest earthquake-safe room or shelter

What is a volcano?

A volcano is an opening in the Earth’s crust through which molten rock, ash, and gases erupt.

What causes volcanoes?

Volcanoes are caused by the movement of magma beneath the Earth’s surface. Magma is molten rock that is formed when the Earth’s mantle is heated. When magma rises to the surface, it can erupt through a volcano.

What are the different types of volcanoes?

There are two main types of volcanoes: shield volcanoes and stratovolcanoes. Shield volcanoes are broad, low volcanoes that are formed by the eruption of fluid lava. Stratovolcanoes are tall, steep volcanoes that are formed by the eruption of thick, viscous lava.

What are the different ways to measure volcanoes?

There are two main ways to measure volcanoes: the Volcanic Explosivity Index (VEI) and the Mercalli intensity scale. The VEI measures the size of a volcanic eruption, while the Mercalli intensity scale measures the effects of a volcanic eruption on the surface.

What are the effects of volcanoes?

Volcanoes can have a variety of effects, including lava flows, ash eruptions, and tsunamis. Lava flows can destroy buildings and other structures, and they can also cause injuries and deaths. Ash eruptions can block roads and railways, and they can also cause respiratory problems. Tsunamis are large waves that can be caused by volcanic eruptions that occur near the coast. Tsunamis can cause extensive damage to coastal areas.

How can we protect ourselves from volcanoes?

There are a number of things that we can do to protect ourselves from volcanoes, including:

• Building our homes and other structures to withstand volcanic eruptions
• Having a plan in place for what to do in the event of a volcanic eruption
• Participating in volcanic eruption drills
• Knowing the location of the nearest volcanic eruption-safe room or shelter

Earthquakes

1. What is an earthquake?
   (A) A sudden movement of the Earth’s crust
   (B) A volcanic eruption
   (C) A tsunami
   (D) A landslide

2. What causes earthquakes?
   (A) The movement of tectonic plates
   (B) The melting of magma
   (C) The release of pressure
   (D) The movement of water

3. What are the different types of earthquakes?
   (A) Tectonic earthquakes, volcanic earthquakes, and man-made earthquakes
   (B) Primary earthquakes, secondary earthquakes, and surface waves
   (C) Foreshocks, mainshocks, and aftershocks
   (D) All of the above

4. What are the effects of earthquakes?
   (A) Ground shaking, damage to buildings and infrastructure, and loss of life
   (B) Tsunamis, landslides, and wildfires
   (C) Volcanic eruptions and earthquakes
   (D) All of the above

5. How can earthquakes be predicted?
   (A) They cannot be predicted with certainty, but scientists can monitor seismic activity to identify areas that are at risk
   (B) They can be predicted with a high degree of accuracy using seismology
   (C) They can be predicted by looking at the weather patterns
   (D) They cannot be predicted at all

Volcanoes

1. What is a volcano?
   (A) A mountain that erupts lava, ash, and gas
   (B) A crack in the Earth’s crust through which magma erupts
   (C) A hot spot on the Earth’s surface where magma rises to the surface
   (D) All of the above

2. What are the different types of volcanoes?
   (A) Shield volcanoes, cinder cones, stratovolcanoes, and calderas
   (B) Active volcanoes, Dormant Volcanoes, and Extinct Volcanoes
   (C) Composite volcanoes, cinder cones, and shield volcanoes
   (D) All of the above

3. What causes volcanoes to erupt?
   (A) The movement of tectonic plates
   (B) The melting of magma
   (C) The release of pressure
   (D) The movement of water

4. What are the effects of volcanoes?
   (A) Lava flows, ash falls, and pyroclastic flows
   (B) Tsunamis, landslides, and earthquakes
   (C) Volcanic eruptions and earthquakes
   (D) All of the above

5. How can volcanoes be predicted?
   (A) They cannot be predicted with certainty, but scientists can monitor seismic activity to identify areas that are at risk
   (B) They can be predicted with a high degree of accuracy using seismology
   (C) They can be predicted by looking at the weather patterns
   (D) They cannot be predicted at all