Natural Disasters (Cyclones, Earthquakes, Volcanoes)
Natural Disasters (Cyclones, Earthquakes, Volcanoes) MCQ Questions
7.
Cyclones which cross 20°N latitude generally exhibit which characteristic, according to NCERT?
A.
They lose the Coriolis force completely
B.
They dissipate immediately without causing damage
C.
They convert into extra-tropical cyclones instantly
D.
They recurve and become more destructive
ANSWER :
D. They recurve and become more destructive
Approach
The question asks about the characteristic behavior of cyclones that cross 20°N latitude, according to NCERT. This relates to the general movement patterns of tropical cyclones and the influence of atmospheric circulation.
Step-by-step
- Understanding Cyclone Movement: Tropical cyclones generally form in the tropics and initially move westward due to the easterly trade winds.
- Influence of Latitude: As they move poleward (away from the equator), especially around 20°N or 20°S latitude, they encounter the subtropical high-pressure belts and the prevailing westerlies.
- Recurving Mechanism: The influence of the subtropical high and the westerlies causes the cyclone's track to change direction. Instead of continuing westward, they tend to "recurve" or turn northeastward in the Northern Hemisphere (and southeastward in the Southern Hemisphere).
- Impact of Recurving: This recurving often brings them closer to landmasses or into regions where they can interact with other weather systems, potentially intensifying or becoming more destructive due to factors like increased moisture, cooler waters, or interaction with upper-level troughs.
- NCERT Reference: NCERT textbooks on Physical Geography (e.g., Class 11) describe this phenomenon, stating that tropical cyclones generally move from east to west but recurve poleward around 20° latitude, often intensifying or becoming more destructive.
Correct Option:
D) They recurve and become more destructive. This option accurately describes the typical behavior of tropical cyclones as they cross 20°N latitude, where they often turn poleward (recurve) and can become more intense or destructive due to changes in environmental conditions and interaction with other weather systems.
Incorrect Options
- A) They lose the Coriolis force completely — This is incorrect. The Coriolis force is present at all latitudes except the equator. While its effect changes with latitude, it does not disappear at 20°N. In fact, it is crucial for the rotation and maintenance of the cyclone.
- B) They dissipate immediately without causing damage — This is incorrect. Cyclones crossing 20°N latitude often continue to be powerful and can cause significant damage. Dissipation usually occurs over land or colder waters, not immediately upon crossing a specific latitude.
- C) They convert into extra-tropical cyclones instantly — While tropical cyclones can undergo a process called "extra-tropical transition" at higher latitudes, this is not an instant conversion at 20°N. It's a gradual process that typically occurs much further poleward (e.g., 30-40°N) as they interact with mid-latitude weather systems and lose their tropical characteristics.
8.
The calm region with subsiding air at the centre of a mature tropical cyclone is called the:
Approach
The question asks to identify the specific region within a mature tropical cyclone characterized by calm conditions and subsiding air. Understanding the structure and dynamics of a tropical cyclone is key to answering this question.
Step-by-step
- Recall the structure of a tropical cyclone: A mature tropical cyclone consists of several distinct regions: the eye, the eyewall, and spiral rain bands.
- Analyze the characteristics of the 'eye': The eye is the central, relatively calm, and clear area at the center of a tropical cyclone. It is characterized by light winds, clear skies (or scattered clouds), and subsiding (sinking) air. This subsidence warms the air and dries it out, leading to the calm conditions.
- Analyze the characteristics of the 'eyewall': Surrounding the eye is the eyewall, which is a ring of intense thunderstorms. This is where the strongest winds, heaviest rainfall, and most violent weather occur. Air here is rapidly rising.
- Analyze the characteristics of 'rain bands': These are spiraling bands of thunderstorms and rain that extend outward from the eyewall. While they bring rain and wind, they are generally less intense than the eyewall.
- Analyze the characteristics of the 'outflow region': This is the upper-level region where air that has risen in the eyewall flows outward away from the storm's center. It is not characterized by subsiding air at the center of the storm.
- Match the description to the correct region: The description "calm region with subsiding air at the centre of a mature tropical cyclone" perfectly matches the characteristics of the eye.
Correct Option:
D) Eye — The eye of a tropical cyclone is a circular area of calm weather, light winds, and often clear skies, found at the center of a mature tropical cyclone. It is formed by strong winds rotating around the storm's center, which causes air to subside (sink) in the middle, leading to warming and drying.
Incorrect Options
- A) Rain band — Rain bands are spiraling bands of thunderstorms and rain that extend outward from the eyewall. While they are part of the cyclone, they are not the central calm region with subsiding air.
- B) Outflow region — The outflow region refers to the upper-level atmosphere where air that has risen in the eyewall flows outward from the storm. It is not the calm, subsiding region at the center.
- C) Eye wall — The eyewall is the most dangerous part of a tropical cyclone, characterized by the strongest winds, heaviest rainfall, and rapidly rising air, directly surrounding the calm eye. It is not a calm region with subsiding air.
9.
In the eye wall of a mature tropical cyclone, wind velocity can reach a maximum of approximately:
ANSWER :
A. 250 km per hour
Approach
The question asks about the maximum wind velocity in the eye wall of a mature tropical cyclone. This requires knowledge of the typical characteristics and intensity of tropical cyclones.
Step-by-step
- Understand Tropical Cyclones: Tropical cyclones are intense low-pressure weather systems that form over warm tropical oceans. They are characterized by strong winds, heavy rainfall, and storm surges.
- Identify Key Regions: A mature tropical cyclone consists of several distinct regions: the eye (a calm, clear center), the eye wall (a band of intense thunderstorms surrounding the eye), and spiral rainbands.
- Locate Maximum Wind Speed: The strongest winds in a tropical cyclone are found in the eye wall, immediately surrounding the calm eye. This is where the most vigorous convection and lowest atmospheric pressure occur.
- Recall Typical Wind Speeds: The wind speeds in the eye wall of a mature tropical cyclone can be extremely high. For a major hurricane or super typhoon, these speeds often exceed 200 km/h. Some of the most powerful cyclones can have winds well over 250 km/h.
- Evaluate Options:
- A) 250 km per hour: This speed is consistent with the maximum wind velocities observed in the eye wall of powerful tropical cyclones.
- B) 50 km per hour: This is a relatively low wind speed, more typical of a tropical depression or a weak tropical storm, not a mature tropical cyclone's eye wall.
- C) 1,000 km per hour: This speed is far too high and unrealistic for atmospheric winds on Earth. It approaches the speed of sound.
- D) 10 km per hour: This is a very light breeze, not associated with any part of a tropical cyclone, let alone its eye wall.
- Conclusion: Based on the typical characteristics of mature tropical cyclones, 250 km per hour represents a realistic maximum wind velocity in the eye wall.
Correct Option: A) 250 km per hour is the correct answer because the eye wall of a mature tropical cyclone is known for its extremely high wind velocities, which can often reach or exceed 250 km/h in strong systems.
Incorrect Options
- B) 50 km per hour: This speed is too low for the eye wall of a mature tropical cyclone. It is more characteristic of a weak tropical storm or a tropical depression.
- C) 1,000 km per hour: This speed is astronomically high and impossible for sustained winds in Earth's atmosphere. It is roughly the speed of sound and not observed in any weather phenomenon.
- D) 10 km per hour: This is a very light wind speed, equivalent to a gentle breeze, and is completely uncharacteristic of a tropical cyclone's eye wall, which experiences the most destructive winds.
10.
The diameter of the circulating system of a mature tropical cyclone can typically vary between:
ANSWER :
C. 150 and 250 km
Approach
The question asks about the typical diameter of the circulating system of a mature tropical cyclone. This requires knowledge of the general characteristics and scale of tropical cyclones.
Step-by-step
- Understand Tropical Cyclones: Tropical cyclones are large-scale weather systems characterized by a low-pressure center, strong winds, and heavy rainfall. They form over warm ocean waters.
- Identify Key Dimensions: A tropical cyclone has several distinct parts, including the eye, eyewall, and spiral rainbands. The "circulating system" refers to the overall extent of the organized cyclonic circulation.
- Recall Typical Sizes: The diameter of the eye of a tropical cyclone can range from a few kilometers to tens of kilometers. However, the entire circulating system, which includes the spiral rainbands extending outwards, is much larger.
- Consult Meteorological Data: According to standard meteorological definitions, the diameter of a typical mature tropical cyclone's circulating system can range from about 100 km to over 2,000 km, with many falling in the 150-250 km range for the most intense wind circulation.
- Evaluate Options:
- A) 5 and 10 km: This is too small, possibly representing only the eye or a very small part of the storm.
- B) 10 and 50 km: This is still too small for the entire circulating system, though it might represent the eye and eyewall region.
- C) 150 and 250 km: This range accurately represents the typical diameter of the strong circulating winds of a mature tropical cyclone.
- D) 1,000 and 2,000 km: While some very large cyclones can reach this size, this is generally considered the upper limit for the entire cloud shield, not the typical diameter of the strong circulating system. Mid-latitude cyclones (extratropical) are often much larger, but the question specifies tropical cyclones.
Correct Option: C) 150 and 250 km
Incorrect Options
- A) 5 and 10 km — This range is too small and typically corresponds to the diameter of the eye of a tropical cyclone, not its entire circulating system.
- B) 10 and 50 km — This range is also too small for the overall circulating system, though it might encompass the eye and eyewall region.
- D) 1,000 and 2,000 km — This range is generally too large for the typical circulating system of a tropical cyclone. While the entire cloud shield can sometimes extend this far, the region of strong, organized circulation is usually smaller. This size is more characteristic of mid-latitude (extratropical) cyclones.
11.
Tropical cyclones generally move in which direction, as per NCERT?
A.
From north to south only
C.
They remain stationary at all times
ANSWER :
D. From east to west
Approach
The question asks about the general direction of movement of tropical cyclones, as per NCERT texts. This requires knowledge of the typical paths taken by these weather phenomena, which are influenced by global wind patterns.
Step-by-step
- Tropical cyclones form over warm ocean waters near the equator.
- In the Northern Hemisphere, these cyclones are initially steered westward by the trade winds, which blow from east to west in the tropical regions (approximately between 5° and 30° latitude).
- As they move poleward (away from the equator), they often encounter the westerlies (winds blowing from west to east) and may recurve, changing their direction towards the east. However, their initial and predominant movement in the tropical regions is westward.
- NCERT texts typically emphasize this initial westward movement due to the influence of the easterly trade winds.
Correct Option:
D) From east to west. Tropical cyclones in the Northern Hemisphere generally move from east to west in their initial stages due to the influence of the trade winds.
Incorrect Options
- A) From north to south only — This is incorrect. Cyclones generally move poleward (away from the equator) and then often recurve.
- B) From west to east — While some cyclones may recurve and move west to east at higher latitudes, their initial and general movement in the tropics is not from west to east.
- C) They remain stationary at all times — This is incorrect. Cyclones are dynamic weather systems that are constantly moving, driven by atmospheric currents.
12.
Why are tropical cyclones generally NOT formed near the equator?
A.
Mountain ranges block all storms near the equator
B.
There is no moisture available at the equator
C.
The Coriolis force is zero at the equator, so the low pressure gets filled instead of intensifying
D.
Sea-surface temperatures are always below 27°C at the equator
ANSWER :
C. The Coriolis force is zero at the equator, so the low pressure gets filled instead of intensifying
Approach
Tropical cyclones require specific atmospheric and oceanic conditions to form and intensify. One crucial factor is the Coriolis force, which is essential for the rotational motion characteristic of these storms. We need to evaluate how the Coriolis force behaves near the equator and its impact on cyclone formation.
Step-by-step
- Understanding Tropical Cyclone Formation: Tropical cyclones are intense low-pressure systems that form over warm tropical oceans. They are characterized by strong winds spiraling inwards towards the center and rising air, leading to heavy rainfall.
- Role of Coriolis Force: The Coriolis force is an inertial force that deflects moving objects (like air currents) in a rotating reference frame. It is responsible for the cyclonic (counter-clockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere) rotation of tropical storms. Without this force, air would flow directly into a low-pressure center, filling it up rather than spiraling and intensifying.
- Coriolis Force at the Equator: The magnitude of the Coriolis force is given by the formula \(F_c = 2mv\Omega \sin(\phi)\), where \(m\) is mass, \(v\) is velocity, \(\Omega\) is the angular velocity of Earth's rotation, and \(\phi\) is the latitude. At the equator, \(\phi = 0^\circ\), and \(\sin(0^\circ) = 0\). Therefore, the Coriolis force is zero at the equator.
- Impact on Cyclone Formation: Because the Coriolis force is negligible or zero at the equator (typically within 5 degrees latitude of the equator), the initial rotation required for a tropical cyclone to develop cannot be sustained. Air parcels attempting to converge into a low-pressure system at the equator would not be deflected into a spiral; instead, they would flow directly towards the low, quickly filling it and preventing intensification. This is why tropical cyclones generally do not form between approximately 0-5 degrees North or South latitude.
Correct Option: C) The Coriolis force is zero at the equator, so the low pressure gets filled instead of intensifying
Incorrect Options
- A) Mountain ranges block all storms near the equator — This is incorrect. While mountain ranges can influence local weather, they do not universally block storm formation across the entire equatorial belt. The primary reason is atmospheric dynamics, not topography.
- B) There is no moisture available at the equator — This is incorrect. The equator is known for abundant moisture due to high evaporation rates from warm ocean waters and the Intertropical Convergence Zone (ITCZ), which is a zone of convergence and rising moist air, leading to frequent rainfall and high humidity.
- D) Sea-surface temperatures are always below 27°C at the equator — This is incorrect. Tropical cyclones require sea-surface temperatures of at least 26.5°C (often rounded to 27°C) to a depth of about 50 meters. Equatorial waters are typically among the warmest on Earth, often exceeding 27°C, providing ample thermal energy for cyclone development. The lack of Coriolis force, not insufficient temperature, is the limiting factor.
