Seasons, Atmosphere and Global Warming | Marvel Semester Series Social Studies Grade 4 | Periwinkle

Key Concepts

Seasons, axial tilt, hemispheres, spring, summer, autumn, winter, climate, weather, equator, water bodies, altitude, atmosphere, troposphere, stratosphere, mesosphere, thermosphere, exosphere, sea breeze, land breeze, water cycle (hydrologic cycle), evaporation, condensation, precipitation, rain, snow, hail, dew, frost, fog, mist, smog, global warming, greenhouse gases, deforestation, fossil fuels, erosion, industrial waste.

Seasons

The Earth experiences seasons due to its axial tilt and its orbit around the sun. The tilt causes different hemispheres to receive varying amounts of direct sunlight throughout the year.

• Axial Tilt: The Earth's axis is inclined, causing different parts of the Earth to receive direct sun rays at different times of the year.
• June Solstice: The North Pole tilts towards the sun, resulting in summer in the Northern Hemisphere.
• December Solstice: The South Pole tilts towards the sun, resulting in summer in the Southern Hemisphere.
• March and September Equinoxes: Both hemispheres receive equal amounts of sunlight, leading to spring and autumn.
• Opposite Seasons: The seasons experienced by the two hemispheres at the same time are opposite.

Types of Seasons

• Spring: Moderate temperatures, cool breeze, equal day and night duration.
• Summer: Longer days, shorter nights, high temperatures. People use coolers, climatizers, and air conditioners. Light-colored cotton clothes are preferred.
• Autumn (Fall): Characterized by falling leaves.
• Winter: Short days, longer nights, low temperatures, cold winds. People wear woolen clothes and use heaters.

Factors Affecting Climate and Weather

Several factors influence the climate and weather of a place.

• Distance from the Equator: Places closer to the equator are warmer.
• Proximity to Water Bodies: Places near seas and oceans have moderate climates.
• Altitude: Higher altitudes experience cooler climatic conditions.

Atmosphere

The atmosphere is divided into five layers:

• Troposphere: The first layer above the Earth's surface where weather changes occur, clouds form, and precipitation happens. Temperature, humidity, air pressure, cloud cover, and altitude play important roles.
• Stratosphere: Contains the ozone layer, which absorbs harmful rays of the sun.
• Mesosphere
• Thermosphere
• Exosphere

The layers of the atmosphere near the surface of the earth are denser than the ones further away.

Sea Breeze and Land Breeze

• Sea Breeze: During the post afternoon, the land heats up faster than the sea. Hot air from the land rises, and cool, humid air from the sea blows towards the land.
• Land Breeze: At night, the land cools down faster than the sea. The air above the sea rises, and cool breeze from the land blows over the sea.

Water Cycle (Hydrologic Cycle)

The water cycle describes the continuous movement of water on, above, and below the surface of the Earth.

• Evaporation: The heat of the sun causes water to evaporate from water bodies. Temperature and wind speed influence evaporation.
• Condensation: Water vapor rises, cools, and condenses into water droplets or snowflakes.
• Precipitation: Clouds release water in the form of rain, snow, or hail.
• Collection: Water flows to rivers, seas, and oceans, and a part of it gets absorbed by the earth as groundwater.
• Transpiration: Trees also play an important role in evaporation of water from land.

Forms of Precipitation

• Rain: Condensed water vapor forms clouds that release water.
• Snow: Condensed water droplets convert into ice in the form of snowflakes in very cold atmospheres.
• Hail: Water droplets freeze into marble-sized pellets of ice, causing hailstorms.

Condensation of Atmospheric Water Vapor

• Dew: Water vapor deposits on warmer surfaces like leaves and stones at night.
• Frost: Dew freezes in cold places where the temperature drops below 0°C. Frost is harmful for crops.
• Fog: A thick cloud of tiny water droplets suspended in the atmosphere. It reduces visibility.
• Mist: Very thin fog, often observed in mountainous terrains.
• Smog: Fog combined with pollutants in cities and towns.

Global Warming

The Earth is naturally warmed by the sun's rays, and greenhouse gases in the atmosphere trap heat. However, increased burning of fossil fuels and deforestation have led to an excess of greenhouse gases.

• Greenhouse Gases: Gases that absorb the heat of the sun and keep the Earth warm.
• Rising Global Temperature: Increased greenhouse gases cause the global temperature to rise.
• Melting Ice Sheets: Rising temperatures lead to the melting of ice sheets.

Effects of Global Warming

• Rising Sea Levels: Melting ice sheets cause sea levels to rise.
• Marine Life Affected: Warming oceans affect marine life.
• Extreme Weather Events: Excessive rains, wildfires, extreme heat waves, and droughts.
• Climatic Imbalance: Untimely rains, increased hurricanes and cyclones.

Human Activities Accelerating Global Warming

• Deforestation: Clearing of land and forest areas for human settlements, industrial development, and agriculture.
• Burning of Fossil Fuels: Vehicular traffic and use of petrol, coal, and natural gas release greenhouse gases.
• Erosion: Clearing of trees accelerates soil erosion, causing landslides and flash floods.
• Emission and Effluence of Industrial Waste: Factories discharge toxic chemical waste into water bodies, harming flora and fauna.

Synthesis/Conclusion

The video comprehensively explains the interconnectedness of seasons, atmospheric phenomena, and the escalating issue of global warming. It highlights how natural processes like the Earth's axial tilt and the water cycle are being disrupted by human activities, leading to significant environmental consequences. Understanding these processes and their impact is crucial for addressing climate change and promoting sustainable practices.