Physical geography

PHYSICAL GEOGRAPHY

GEOGRAPHY - LESSON 9835

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PLATE TECTONICS

tHE WORLD'S CLIMATE

THE WATER CYCLE

WINDS AND OCEAN CURRENTS

THE WORLD'S BIOMES AND ECOSYSTEMS

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PLATE TECTONICS

EARTH'S LAYERS

It shows that the earth is made up of three layers—the core, the mantle, and the crust. The core is located at the very centre. It is made up of iron and nickel. The middle layer is the mantle. This is a layer of hot, molten rock. The outer layer is the earth’s crust. The crust is broken into more than a dozen great slabs of rock called tectonic plates. These plates float on a partially melted layer of the mantle. The plates carry the earth’s continents and oceans.

EARTH'S tectonic plates

tectonic plates

The theory of plate tectonics explains how most of the major features of the earth’s surface were formed. According to this theory, tectonic plates have been moving and shaping the surface of the earth for 2.5 to 4 billion years. Most of the time, plate movement is so gradual—only 10 cm a year—that it cannot be felt. The way the plates move determines the kinds of landforms that are formed. It also determines where earthquakes occur.

Winds and ocean currents

What is wind?

Wind is air that moves across the earth’s surface. Winds occur because the sun heats up the earth’s atmosphere and surface unevenly. When the sun heats the air over the Equator, the warm air becomes lighter, rises, and creates areas of low pressure. Cool air from the Poles is heavy, tends to sink, and creates areas of high pressure. The cool air blows in to replace the rising warm air at the Equator. These movements over the earth’s surface cause winds, which distribute the sun’s heat around the planet.

Wind patterns

winds and latitudes

When the cold air of the polar easterlies meet the warmer air of the westerlies, they form a front. Stormy weather usually occurs when two different types of air meet. Near the Equator global winds are diverted north and south, leaving a generally windless band called the doldrums. The doldrums are calm; winds almost disappear. How do you think the doldrums might affect the temperature of places on Earth?

Ocean currents

The world’s winds also help move the ocean currents. These are the cold and warm streams of water that move through the oceans.As ocean currents circulate, cold water from the Poles moves slowly toward the Equator. This water warms as it moves through the low latitudes, forming warm ocean currents. The warm water, in turn, moves away from the Equator. As it moves, it cools to become a cold ocean current. Ocean currents affect climate in the coastal lands along which they flow. Cold ocean currents help to cool the lands they pass. Warm ocean currents bring warmer temperatures.

Ocean currents

The world's climate

CLimates - why are they different?

Climate refers to the weather patterns in a place over a long period of time. The climate of a place depends on the amount of direct sunlight it receives. Places near the Equator receive direct sunlight year-round. In contrast, the North Pole never receives direct sunlight. The sun is not the only factor that affects climate. Wind, ocean currents, and landforms also determine the climate of an area.

CLimate zones

Geographers often divide the earth into climate zones—tropical, dry, middle latitude, high latitude, and highlands. Because climates vary within these broad regions, geographers further divide the major regions into smaller ones. The temperatures and precipitation that are generally found in each of the major climate zones are displayed in the next slide.

world climate zones

world climate zones

the world's biomes and ecosystems

World of plants and animals

World of living things

By now, you should know that some animals only live in certain places. For example, it would be extremely unlikely to find a penguin on any beach near the equator. Plants and animals depend on each other for survival - it's the cycle of life. A plant and animal community that covers a large geographical area is called a biome. A biome has certain kinds of plants and animals. It is located in a specific climate and generally has a specific kind of soil. Remember how cacti only grew in dry areas?

terrestrial biomes

Biomes - World of living things

By now, you should know that some animals only live in certain places. For example, it would be extremely unlikely to find a penguin on any beach near the equator. Plants and animals depend on each other for survival - it's the cycle of life. A plant and animal community that covers a large geographical area is called a biome. A biome has certain kinds of plants and animals. It is located in a specific climate and generally has a specific kind of soil. Remember how cacti only grew in dry areas?

Biomes

ecosystems

A biome can include several ecosystems. An ecosystem refers to all the living things and nonliving things within a certain areaand the relationships among them. Living things include the plants, animals, and microbes (such as bacteria and fungi). The nonliving environment includes air, soil, water, and sunlight. An ecosystem contains everything that is needed for the plants and animals living there to survive.

Biomes vs ecosystems

the food chain

The relationship of living and nonliving things in an ecosystem can be seen in the food chain.The food chain shows how the living and nonliving parts of an ecosystem are interrelated. The sun provides the energy that the primary producers need to make food. Primary producers are mainly green plants. Plants also need things such as water and minerals from the soil to grow. Primary consumers include animals that eat plants, such as rabbits and grasshoppers. Secondary consumers are predators, or animals that eat other animals. Finally, decomposers, such as bacteria, break down dead animals and plants into nutrients that go back into the soil. The nutrients are used again by plants.

The food chain

the water cycle

the water cycle

The water cycle, which is the movement of water from the oceans to the air to theground and finally back to the oceans. The total amount of watern on Earth does not change, but the Earth’s water is constantly moving. As water moves through the water cycle, it becomes mixed with water from all over the earth—and sooner or later, water that once fell on a dinosaur falls on you. The sun drives this endless cycle by evaporating water from the surfaces of oceans, lakes, and streams. Precipitation falls in various forms—rain, snow, sleet, or hail. Some precipitation immediately evaporates and returns to the atmosphere.

The water cycle

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