Latitude

1. Definition and Measurement

• Latitude is the measurement of a place's position north or south of the equator.

• It is measured in degrees (°), minutes, and seconds.

• The starting point for measurement is the equator, which is assigned a value of 0°.

• The maximum possible latitudes are 90° N at the North Pole and 90° S at the South Pole.

2. Characteristics of Lines of Latitude

• Lines of latitude are also called parallels because they run parallel to the equator and to each other.

• They run horizontally from east to west.

• These lines do not meet or intersect.

• The circles formed by these lines become smaller as they approach the poles.

3. Five Lines of Latitude

1. Equator (0°): The "great circle" that is equidistant from the poles and divides the Earth into the Northern and Southern Hemispheres.

2. Tropic of Cancer (23.5° N).

3. Tropic of Capricorn (23.5° S).

4. Arctic Circle (66.5° N).

5. Antarctic Circle (66.5° S).

4. Relationship Between Latitude and Climate

• The closer a latitude is to the equator, the warmer the climate.

• The closer a latitude is to the poles, the colder the climate.

• The Tropics: The area between the Tropic of Cancer and Tropic of Capricorn; it experiences a tropical climate with average annual temperatures above 18°C.

• Temperate Zones: Areas between the tropics and the polar circles; these regions experience four seasons (winter, spring, summer, autumn).

• Polar Regions (Frigid Zones): Areas within the Arctic and Antarctic Circles; it is cold all year round with temperatures rarely exceeding 10°C.

Longitude

1. Definition and Measurement

• Longitude consists of imaginary lines that run vertically from the North Pole to the South Pole.

• These lines are used to measure distance east or west of a starting reference point.

2. Reference Lines

1. Prime Meridian (0°): The reference line passing through Greenwich, England; it divides the Earth into the Eastern and Western Hemispheres.

2. Antemeridian (180°): The line directly opposite the prime meridian; it represents the boundary of the eastern and western hemispheres on the other side of the world.

The Earth’s Grid System

1. Purpose and Composition

• The earth's grid or coordinate system is used to determine the exact position of any place on Earth.

• It is formed by the intersection of horizontal (latitude) and vertical (longitude) lines.

Layers of the Atmosphere

1. Composition of the Atmosphere

• The atmosphere is a "blanket of air" or "jacket" surrounding the Earth.

1. Major Gases: Nitrogen (78%) and Oxygen (21%).

2. Trace Gases: The remaining 1% includes water vapor, carbon dioxide, ozone, argon, neon, helium, hydrogen, and chlorofluorocarbons (CFCs).

2. The Five Layers (Divided by Temperature Profile)

1. Troposphere (0–10/14.5 km): The lowest layer where nearly all weather phenomena occur. Temperature decreases as altitude increases. Analogy: It is like water heating in a pan—it's hottest at the bottom near the "stove" (Earth's surface) and cools as you go up.

2. Stratosphere (up to 50 km): Contains the ozone layer, which absorbs harmful ultraviolet (UV) radiation. Temperature increases with altitude because of this absorption.

3. Mesosphere (50–80 km): The coldest layer (average -90°C) where meteors burn up due to friction with thin air.

4. Thermosphere (80–110 km): Contains the ionosphere, which bounces off radio waves. This layer is where auroras (Northern and Southern Lights) occur. Temperature increases significantly here due to solar radiation.

5. Exosphere (above 700 km): The outermost layer with very thin air; it transitions into outer space and is where satellites are stationed.

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Greenhouse Effect

1. Mechanism of the Natural Process

The greenhouse effect is the process by which Earth's atmosphere warms the surface.

How it works: Sunlight enters the atmosphere; some is reflected, but much is absorbed by the Earth and re-radiated as infrared heat. Greenhouse gases trap this heat, preventing it from escaping into space.

2. Greenhouse Gases and Human Impact

Common greenhouse gases include carbon dioxide (CO2 ), methane (CH  ), water vapor, and ozone (O ). Human activities, such as burning fossil fuels and deforestation, increase CO2 levels.

Global Warming: The potential increase in average global temperatures resulting from an enhanced greenhouse effect.

Behaviors of Heated Air and Surrounding Air

1. Differential Heating

Specific heat capacity is the amount of heat needed to raise the temperature of 1 gram of a substance by 1°C.

Sand vs. Water: Sand has a low specific heat and heats up/cools down faster than water. Water has a high specific heat and changes temperature slowly.

2. Air Movement and Density

• Density is how tightly packed molecules are in an object.

• When air is heated, it expands, becomes less dense, and rises.

• Cool air is denser and sinks, moving in to replace the rising warm air.

• Convection: The transfer of heat by the movement of a heated fluid like air.

3. Air Pressure and Wind

• Rising warm air creates an area of low pressure.

• Sinking cool air creates an area of high pressure.

• Wind is the movement of air from areas of high pressure to areas of low pressure.

Atmospheric Phenomena: Breezes, Monsoon, and Intertropical Convergence Zone (ITCZ)

1. Local Breezes

1. Sea Breeze: Occurs during the day when warm air over land rises and cool air from the sea moves in to replace it.

2. Land Breeze: Occurs at night when land cools faster than the sea; warm air over the sea rises and cool air from the land moves out to sea.

2. Monsoons

Monsoons are major wind systems characterized by dramatic seasonal changes in direction.

• Northeast Monsoon (Amihan): Affects the Philippines from October to March; brought by cold air from Siberia, resulting in cloudiness and light to moderate rain.

• Southwest Monsoon (Habagat): Affects the Philippines from July to September; brought by warm, moist air from the equatorial oceans, resulting in heavy rainfall and humid weather.

3. Intertropical Convergence Zone (ITCZ)

• A band of clouds and thunderstorms that encircles the globe near the equator.

• It is the place where winds from the tropics meet or converge.

• As warm air rises at the equator, it cools and vapor pressure condenses, forming clouds and rain.

How far is the Sun in the Sky?

1. Earth's Rotation

• The Earth spins on its axis, an imaginary line through its center.

• One complete spin is a rotation, which takes 24 hours and causes day and night.

• The axis is tilted at 23.5° from the vertical.

2. Earth's Revolution and Orbit

• The Earth moves around the Sun in a path called an orbit. This motion is called revolution.

• The orbit is an elliptical (oval) shape, not a perfect circle.

• One revolution takes approximately 365 1/4 days (one year). Every four years, the remaining quarters are added to make a leap year of 366 days.

1. Perihelion: The point in the orbit where Earth is closest to the Sun (around January 3rd).

2. Aphelion: The point in the orbit where Earth is farthest from the Sun (around July 4th).

3. The Sun's Height and Seasons

Seasons are caused by the tilt of the Earth's axis as it orbits the Sun.

• Summer Solstice (June 21): The Northern Hemisphere is tilted toward the Sun; the Sun reaches its highest point in the sky at noon at the Tropic of Cancer.

• Winter Solstice (December 21): The Southern Hemisphere is tilted toward the Sun; the Sun is at its highest altitude over the Tropic of Capricorn.

• Equinox (March 21 and September 23): Neither pole is tilted toward the Sun; the Sun is directly overhead at the equator (subsolar point).

• Energy Received: The higher the Sun is in the sky, the more energy is received per unit area, leading to warmer temperatures.

Glossary

• Amihan: The northeast monsoon in the Philippines, characterized by cold winds and light rain.

• Antemeridian: The longitude line at 180°, opposite the prime meridian.

• Aphelion: The point in Earth's orbit where it is farthest from the sun.

• Atmosphere: The blanket of air surrounding the Earth.

• Aurora: A display of glows in the night sky (Northern or Southern Lights) occurring in the ionosphere.

• Axis: The imaginary line that runs through the center of the Earth from pole to pole.

• Convection: Heat transfer through the movement of heated fluids like air.

• Density: A measure of how much mass is in a given volume of a substance.

• Equator: The horizontal imaginary line at 0° latitude that divides the Earth into Northern and Southern Hemispheres.

• Equinox: The time of year when the sun is directly overhead at the equator, and day and night are roughly equal in length.

• Global Warming: The increase in average global temperature caused by excessive greenhouse gases.

• Greenhouse Effect: The natural process by which gases in the atmosphere trap heat to keep Earth warm.

• Habagat: The southwest monsoon in the Philippines, characterized by heavy rains and humid weather.

• ITCZ (Intertropical Convergence Zone): A band of clouds near the equator where winds from the northern and southern hemispheres meet.

• Latitude: Imaginary horizontal lines used to measure distance north or south of the equator.

• Longitude: Imaginary vertical lines used to measure distance east or west of the prime meridian.

• Monsoons: Wind systems that undergo seasonal changes in direction.

• Ozone Layer: A region in the stratosphere that absorbs harmful UV radiation from the sun.

• Perihelion: The point in Earth's orbit where it is closest to the sun.

• Prime Meridian: The starting point for longitude (0°), passing through Greenwich, England.

• Rotation: The spinning of the Earth on its axis.

• Revolution: The movement of the Earth around the sun in its orbit.

• Solstice: The time of year when the sun reaches its highest or lowest point in the sky at noon, marking the start of summer or winter.

• Specific Heat Capacity: The amount of heat required to raise the temperature of a substance.

• Subsolar Point: The location on Earth where the sun is directly overhead at solar noon.

References

DepEd Tambayan. (n.d.). Grade 7 science module: Locating places of the Earth. DepEd Tambayan. Retrieved March 8, 2026, from https://depedtambayan.net/grade-7-science-module-locating-places-of-the-earth/

DepEd Tambayan. (n.d.). Grade 7 science module: You keep me warm. DepEd Tambayan. Retrieved March 8, 2026, from https://depedtambayan.net/grade-7-science-module-you-keep-me-warm/

DepEd Tambayan. (n.d.). Grade 7 science module: Rise above, sink below, and blow around. DepEd Tambayan. Retrieved March 8, 2026, from https://depedtambayan.net/grade-7-science-module-rise-above-sink-below-and-blow-around/

DepEd Tambayan. (n.d.). Grade 7 science module: Earth around the Sun. DepEd Tambayan. Retrieved March 8, 2026, from https://depedtambayan.net/grade-7-science-module-earth-around-the-sun/