In-text — Cyclones — Pressure, Winds, Storms, and Cyclones

1. 15 marksCuriosity Grade 8, Chapter 6, page 92, section 6.6

   Explain how a storm becomes a cyclone. What is a cyclone?

   Hint. Two steps are added to the ordinary storm chain — find both.

   Where cyclones form. Cyclones are large storms that form over warm ocean waters.

   The chain, as the chapter gives it:

   1. As the ocean water gets heated, the warm and moist air above it rises.
   2. As the moist air rises, the water vapour condenses to form raindrops.
   3. The first extra step — heat is released. We know that during evaporation, water takes up heat to change into vapour. When this water vapour condenses into raindrops, heat is released back into the atmosphere. This causes further warming of the ascending air leading it to rise even further, creating an even lower pressure.
   4. Air from the surrounding regions rushes in and it also starts rising.
   5. The second extra step — the spin. Earth's rotation causes the moving air to spin (Fig. 6.19).
   6. This cycle is repeated, resulting in the creation of a very low-pressure area with high-speed winds revolving around it.

   Definition. This spinning system of clouds, winds, and rain is called a cyclone.

   ✦ Step 3 is what makes a cyclone so much more violent than an ordinary storm, and it is a genuine feedback loop. Rising moist air condenses; condensing releases heat; the released heat warms the air further; warmer air rises faster; faster rising draws in more moist air, which condenses in turn. Each round of the cycle deepens the low pressure, and a deeper low means faster winds.

   Step 5 is what makes it a cyclone rather than just a very strong storm. Without the spin there is no revolving system and no eye.

   This is exercise question 8.

2. 23 marksCuriosity Grade 8, Chapter 6, page 92

   What is the eye of a cyclone? What is the weather like there?

   Hint. The answer is the opposite of what the word 'cyclone' suggests.

   Definition. In a cyclone, the region of lowest pressure is at the centre, known as the eye of the cyclone.

   The weather there. At the eye of the cyclone, the wind is calm, but the surrounding region experiences strong winds and heavy rainfall.

   	The eye	The surrounding region
   Pressure	Lowest in the whole system	Higher
   Wind	Calm	Strong
   Rain	—	Heavy rainfall

   ✦ The eye is calm even though it is the lowest-pressure point, which sounds contradictory. It is not: what drives wind is a pressure difference between two places, and the centre is the one place where you are not on a slope of pressure — the pressure is equally low all around you. The strongest winds are just outside it, where the pressure changes most steeply. Fig. 6.19 shows this as closely-spaced values falling from 1008 mb to 994 mb.

   Why this makes a cyclone dangerous in an unexpected way. People caught in a cyclone sometimes come out when the eye passes over, believing the storm has ended — and are then caught by the far wall of the cyclone, with winds as strong as before and blowing the opposite way.

   This is why exercise 2(iii) is false: Weather is stormy at the eye of a cyclone.

3. 34 marksCuriosity Grade 8, Chapter 6, pages 92-93

   What happens to a cyclone when it reaches land? Why?

   Hint. Ask what the cyclone was living on while it was over the sea.

   It weakens. As a cyclone moves from the ocean towards the land, it generates higher wind speeds compared to the wind speeds produced by regular thunderstorms. Once the cyclone reaches land, the source of moist air is cut off and it gradually loses its strength.

   Why the moisture is what matters. The feedback that drives a cyclone runs on condensation: moist air rises, its vapour condenses, heat is released, the air rises further, the pressure falls further. Warm ocean water keeps feeding moist air into that cycle. Over land there is no such supply, so the loop starves and the system winds down.

   ✦ But weakening is not the same as being harmless. The chapter is emphatic: Even as a cyclone loses its strength while travelling over land, it leaves behind a trail of destruction that can take months or even years to repair.

   The example the chapter gives: the Amphan cyclone in 2020 had peak wind speeds of 270 km/h.

   And the storm surge. Strong winds during a cyclone push ocean water towards the shore, creating a wall of water that can be as high as 3–12 metres. This surge of water can flood coastal areas and even areas far from the sea.

   Use the chapter's figures — 270 km/h for Amphan, 3–12 m for the surge — and do not add others from memory. The book names exactly one cyclone, and any further examples need a source you have actually checked.

4. 45 marksCuriosity Grade 8, Chapter 6, page 93

   List the kinds of damage a cyclone causes, as the chapter describes them.

   Hint. The chapter gives seven distinct consequences — several of them long after the wind has gone.

   The chapter's list:

   Damage	The chapter's words
   Storm surge and flooding	Strong winds push ocean water towards the shore, creating a wall of water ... 3–12 metres. It can flood coastal areas and even areas far from the sea
   Rivers overflowing	The heavy rainfall which accompanies a cyclone may cause rivers to overflow
   Landslides	It can also trigger landslides
   Drinking water contaminated	Seawater that rushes inland can contaminate drinking water sources
   Farmland damaged	It can damage farmland. The salt in seawater can make soil less fertile, affecting crops
   Roads blocked	Roads may get blocked due to fallen trees and debris, making it difficult for help to reach the affected areas
   Power outages	Power outages can last for days, disrupting emergency services and daily life

   ✦ Notice how many of these are not caused by the wind at all. Salt in the soil, contaminated wells, blocked roads and days without electricity are consequences that arrive after the cyclone has passed, and they are what make the recovery take months or even years. A cyclone is not simply a few hours of high wind.

   And the effects compound each other, which is why the recovery is so slow. Blocked roads mean help cannot reach the people who need it, and power failures disable the emergency services that would clear those roads. Salted farmland means crops fail in the following season too, because the salt stays in the soil long after the immediate damage has been repaired.

5. 54 marksCuriosity Grade 8, Chapter 6, page 93

   How can we protect ourselves during cyclones? What role does the India Meteorological Department play?

   Hint. Warning is one half of the answer; what you do with the warning is the other.

   The chapter's advice:

   1. It is important to stay updated on weather reports and periodic alerts, and warnings issued by the India Meteorological Department (IMD).
   2. If you live in a cyclone-prone area, keep an emergency kit ready with essential items.
   3. During a cyclone, quickly move to a nearby designated cyclone shelter.

   The IMD's role. The India Meteorological Department (IMD) constantly monitors cyclones and thunderstorms in India (Snapshots), and issues the alerts and warnings the public acts on.

   What makes the warnings possible. Thanks to the weather monitoring satellites, today we can track cyclones and predict their path, helping us reduce their impact on life and property. Several national and international organisations work together to monitor cyclone-related disasters.

   ✦ The three pieces of advice are deliberately in that order — and it is a before/before/during sequence. Staying informed and preparing a kit both have to happen before a cyclone arrives; once it is upon you there is only time to move to shelter. Preparation that is left until the warning comes is preparation that does not happen.

   And this is why tracking matters so much. A cyclone cannot be prevented or steered. What satellites and the IMD change is how much warning people get — which decides whether the shelters fill in time.

   The chapter names IMD and satellites and gives no other organisations, dates or statistics. Keep your answer to what it gives, and cite a source for anything more.

6. 63 marksCuriosity Grade 8, Chapter 6, page 92, Fig. 6.19

   Fig. 6.19 marks pressures of 994 mb, 996 mb, 998 mb and 1008 mb around a cyclone. Read the figure and explain what it shows.

   Hint. Where is the smallest number, and what does the size of the gap between numbers tell you?

   What the figure shows. Bands of decreasing pressure closing in on the centre, with arrows showing winds blowing from high pressure areas to low pressure areas:

   Value	Where
   1008 mb	The outer region, marked High pressure
   998 mb → 996 mb → 994 mb	Progressively closer to the centre
   994 mb	At the centre, marked Low pressure

   What it means. The centre is the lowest-pressure point — the eye. Since air moves from high pressure to low, air from all around rushes inward, and Earth's rotation makes that inrushing air spin.

   ✦ The total drop is only 14 mb — and that is the point worth noticing. Ordinary atmospheric pressure is about 1000 mb, so a cyclone's centre is roughly 1.4% below its surroundings. That tiny-looking difference produces winds that reached 270 km/h in Amphan. Wind speed depends on the pressure difference, and it does not take much of one to produce a great deal of wind.

   Reading it in pascal, using the A step further box (1 mb = 100 Pa): the drop is 1400 Pa, out of about 1,00,000 Pa. This is exactly why weather maps are drawn in millibars — in pascal the interesting difference would be buried in the last digits.

   And the closeness of the bands matters too. Where the values crowd together, the pressure changes steeply over a short distance, and that is where the strongest winds are — just outside the calm eye.

7. 74 marksCuriosity Grade 8, Chapter 6, page 93, Let us wrap up

   Set out the chapter's own summary chain from heated air to lightning, in order.

   Hint. Seven steps, given as a flow at the end of section 6.6.

   The chapter's Let us wrap up! sequence:

   1. Warm air rises, creating a low-pressure area.
   2. Cool air rushes to occupy the low-pressure area.
   3. Warm air rises, cools, and the water vapour condenses to form clouds.
   4. Bigger water drops in the clouds fall to the ground as rain, hail, or snow.
   5. Positive and negative charges are created in the clouds by strong winds blowing upwards and downwards.
   6. When positive and negative charges meet, they cause lightning. Lightning may occur within a cloud, between clouds, or between a cloud and the ground.
   7. Under certain weather conditions, storms may develop into cyclones.

   ✦ One idea runs through the whole list: air moving because of a pressure difference. Steps 1 and 2 are that idea stated plainly. Steps 3 and 4 are what happens to the moisture the rising air carries with it. Steps 5 and 6 are what happens to the water and ice when the winds are strong enough to rub them together. Step 7 is the whole process running away with itself over a warm ocean.

   Where the two ingredients enter. Important requirements for the formation of thunderstorms are moisture and strong winds — moisture at steps 3 and 4, strong winds at step 5.

   Use this chain as a checklist when answering exercises 8 and 11. Those questions ask for a process, and the marks are in the order and the completeness of the steps, not in any single sentence.

Solutions written by the tuition.in editorial team and checked against NCERT Curiosity, Textbook of Science for Grade 8, Chapter 6 'Pressure, Winds, Storms, and Cyclones', book pages 80-97 (hecu106.pdf, 18 pages, Reprint 2026-27), downloaded from ncert.nic.in and read page by page. Every activity number, figure number, quantity and quoted sentence below was checked against that PDF. THREE FIGURES WERE MEASURED, NOT EYEBALLED, because three exercise answers turn on them. Fig. 6.22 (exercise 1(iv)) was rendered at 900 dpi and the vessel walls located from the dark outlines: vessel A is 519 px wide and vessel B is 726 px, so B is 1.40x wider, while the water columns measure 660 px and 671 px - equal to within 1.7%, matching the question's premise of equal levels. Hence P_A = P_B but F_A < F_B, answer (b). Fig. 6.24 (exercise 7) was segmented by colour: the two balloons occupy identical vertical ranges (rows 1260-1403, centroids both at row 1334), so they are at exactly the same height and bulge equally. Fig. 6.25 (exercise 9) was measured by tracking the palm trunks: the leftmost trunk's centre moves from x=655 at the top to x=763 near the base, so the crown sits about 108 px LEFT of the base, and all four crowns stream leftwards - the wind blows from B to A. Since a summer afternoon gives a SEA BREEZE (sea to land), B is the sea and A is the land. Fig. 6.21 was also rendered and confirmed to show the three vessels JOINED BY TUBES near their bases, which is what makes answer (d) correct. The chapter's own atmospheric-pressure figure was checked rather than assumed: 2250 N over 15 cm x 15 cm = 0.0225 m^2 gives 1,00,000 Pa = 1000 hPa = 1000 mb, which sits squarely inside the 994-1008 mb range marked on Fig. 6.19, so the book's number is internally consistent. Two deliberate restraints. (1) The chapter names exactly ONE cyclone (Amphan 2020, peak winds 270 km/h) and one surge range (3-12 m), and gives no cyclone categories, no casualty figures, no monsoon rainfall percentages and no atmospheric composition percentages. None are supplied here; the research projects tell the student to cite IMD or an equivalent checked source and to report disagreement between sources rather than pick a number. (2) Lightning-safety advice is reproduced exactly as the book gives it, with nothing added, since an invented extra rule could put someone at risk.. Questions are referenced from the NCERT textbook for identification.