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Geography Chapter 2 Notes The Water Cycle Seventy percent of the earth’s surface is covered with water. There is water literally all around us in the form of water vapor, or water in the atmosphere in the form of gas. Although the amount of water does not change, its form does. Water in oceans goes to the air, then to the ground, and finally returns to the oceans. This is known as the water cycle. The sun’s heat turns liquid water into water vapor, or humidity. This process is known as evaporation. As water vapor rises and cools, it changes back into liquid in a process called condensation. Tiny droplets of water form clouds and fall back to the earth in the from of precipitation—rain, snow, sleet, or hail. Precipitation soaks into the ground and collects in stream and rivers. During collection, streams and rivers carry the water back to the oceans. Water Resources • Only about 2 percent of the water found on the earth is freshwater. • Of that 2 percent, about 1.6 percent is frozen into giant sheets of ice, or glaciers. • Groundwater fills tiny cracks and holes in the rock layers below the earth’s surface. • There is 10 times more groundwater than there is water in rivers and lakes. • Some of this water flows through underground rock layers called aquifers. • The earth’s four major oceans—the Pacific, Atlantic, Indian, and Arctic Oceans—contain salt water, which is not fit for human consumption. Section 2 Weather and Climate • Weather refers to the unpredictable changes in air that take place over a short period of time. • Climate is the usual, predictable pattern of weather in an area over a long period of time. • Climate is affected by the sun, the wind, the oceans and other bodies of water, landforms, and even people. • To understand an area’s climate, scientists look at extremes of temperature and precipitation. The Sun and Climate • The original source of climate is the sun. • Wind and water carry the sun’s heat around the globe. • A place’s climate is also affected by its latitude. • The sun’s rays hit the earth more directly at low latitudes. • Places at higher latitudes receive only angled rays of the sun. • The areas near the Equator are known as the Tropics. • They lie between the Tropic of Cancer (23½°N latitude) and the Tropic of Capricorn (23½°S latitude). • The Tropics experience a hot climate year-round. The Wind’s Effect on Climate • Movements of air are called winds. • Winds follow typical patterns, affecting climate. Monsoons are powerful seasonal winds that blow over continents for months at a time. They are found mainly in Asia and some areas in Africa. Thunderstorms sometimes produce tornadoes, or funnel-shaped windstorms. Although they occur all over the world, the United States experiences more tornadoes than any other area. • Violent tropical storms called hurricanes form over the warm waters of the Atlantic Ocean in the late summer and early fall. • Hurricanes usually strike the Caribbean islands and North America. • When the same type of storm hits Asia, it is called a typhoon. • A long period of extended dryness is called a drought. • El Niño—a unique combination of temperature, wind, and water effects in the Pacific Ocean—last occurred in 2004. • El Niños occur about every three years and form when cold winds from the east are weak and the Pacific Ocean gets warmer than usual. • When the opposite kind of unusual weather takes place, the event is known as La Niña. Ocean Currents • Moving streams of water called currents carry warm or cool water through the world’s oceans. • These currents affect the climate of land areas. • Winds that blow over warm currents, for example, carry warm air to land areas. Landforms and Climate • The shape of land and the location of landforms in relation to one another and to water also affect climate. • Local winds are patterns of wind caused by landforms in a particular area. • Some local winds occur because land warms and cools more quickly than water. • As a result, cool sea breezes keep coastal areas cool during the day. • After the sun sets, the land cools down, and cool breezes blow out to sea. • The higher the elevation a place has, the cooler it will be. • As air moves up the windward side of mountain peaks, it becomes cool and loses its moisture. • The air that crosses over the peaks is dry, creating a rain shadow. • A rain shadow is a dry area on the leeward side of the mountains. • The dry air of a rain shadow warms up again as it moves down mountainsides, giving the region a dry or desert climate. The Impact of People on Climate • People’s actions affect climate. • For example, cities are warmer than rural areas because streets and buildings absorb more heat than plants and trees do. • In addition, people burn fuels, which raises temperatures. • In the past 200 years, people have burned coal, oil, and natural gas as sources of energy. • The buildup of the gases from the burning of these substances has prevented warm air from rising and escaping into the atmosphere. • This is known as the greenhouse effect, in which the earth’s temperature will increase. • Dense forests that receive high amounts of rain each year are known as rain forests. • People burn trees to clear rain forests, which leads to the greenhouse effect. • Also, less water evaporates if there are fewer trees, decreasing rainfall. • • • • Section 3 Tropical Climates • • There are two types of tropical climates—tropical rain forest and tropical savanna. Areas with a tropical rain forest climate have year-round rains that produce lush vegetation and thick rain forests. • Tall hardwood trees such as mahogany, teak, and ebony form a canopy, or top layer of the forest. • Tropical savanna areas have a definite wet season, while the remainder of the year is hot and dry. • Savannas, or broad grasslands with few trees, are found in these areas. Mid-Latitude Climates • Mid-latitude climates include more and different climate zones. • This is due to a mix of air masses: warm air from the Tropics and cool air from the Polar Regions. • The marine west coast climate occurs along coastal areas that receive winds from the ocean. • Winters are rainy and summers are cool in these areas. • Deciduous and coniferous trees grow in this climate. • The coastal Mediterranean climate also has rainy, mild winters. • It differs from the marine west coast climate in that the Mediterranean climate experiences hot, dry summers. • Shrubs and short trees grow in this climate. • The humid continental climate occurs in the inland areas of North America, Europe, and Asia. • Winters can be long, cold, and snowy. • Summers are short and may be very hot. • Deciduous trees and vast grasslands grow here. • Mid-latitude regions close to the Tropics experience a humid subtropical climate where rain falls throughout the year. • Oak, magnolia, and palm trees grow here. High Latitude Climates • In the high latitudes nearest the mid-latitude zones, you will find the subarctic climate. • Winters are severely cold and bitter. • Huge evergreens forests called taiga grow here. • Closer to the Poles than the subarctic zone lie areas of vast rolling plains without trees. • This region is known as the tundra and is harsh and dry. • In these parts, much of the lower layers of soil stay permanently frozen and are known as permafrost. • Only sturdy grasses and low berry bushes grow here. • The ice cap climate is found at the Poles and on the ice sheets of Antarctica and Greenland. • No vegetation grows here. • Only lichens can live on the rocks. Dry Climates • Desert climates—the driest climates—have less than 10 inches of rainfall a year. • Only scattered plants like cacti can live here. • Many deserts are surrounded by partly dry grasslands known as steppes. • The Great Plains of the United States has a steppe climate, that averages 10 to 20 inches of rain a year. Highland Climate • Mountains tend to have cool climates—even near the Equator. • • A highland, or mountain, climate has cool or cold temperatures throughout the year. No trees grow above the timberline. Section 4 The Atmosphere • The atmosphere is the blanket of gases, or air, surrounding the earth. • Air pollution consists of fumes and chemicals from vehicles and industries. • It also includes solid particles such as ash and dust. • Global effects of air pollution include global warming, ozone depletion, and acid rain. • The ozone layer, which filters out harmful sun rays, is being depleted by chemicals in air pollution. • When chemicals in air pollution combine with precipitation, they can create acid rain, which kills fish and forests. The Lithosphere • The lithosphere is the earth’s hard outer shell, or what we call the land areas. • The lithosphere can be damaged by mining for minerals and ores such as copper and iron. • If not properly managed, rich topsoil can be carried away by wind and water. • Deforestation, or cutting down forests without replanting, can cause topsoil to be lost. • Farmers can enrich topsoil by using fertilizers and practicing crop rotation, which involves changing what is planted in a field. The Hydrosphere • The hydrosphere includes all the water in the oceans, lakes, rivers, glaciers, and so forth, plus precipitation. • Because people, plants, and most animals require freshwater, it is important that it be carefully managed. • Conservation is an important part of water management and involves not wasting water. • Another part of water management involves avoiding polluting water. • In irrigation, water is collected and distributed to crops. • As much as 70 percent of all water is used for farming, and most irrigation methods are wasteful. • Some industrial processes result in dangerous chemicals entering the water supply. • Pesticides, or powerful chemicals that kill crop-destroying insects, can seep into water and pollute it. The Biosphere • The biosphere includes all living things along with the environments in which they live. • As humans expand their communities, they invade ecosystems, or places where plants and animals are dependent on one another and their surroundings. • Changes that humans make, such as draining wetlands, can destroy the balance of ecosystems. • People are learning the importance of protecting ecosystems. • Sometimes the need to protect the environment clashes with people’s survival needs, requiring that new ways be found to meet these needs. Section 1: The Water Planet Main Idea Water is one of the earth’s most precious resources. • Region Water covers about 70 percent of the earth’s surface. • Movement Water follows a cycle of evaporation, condensation, precipitation, and collection on and beneath the ground. • Science Humans and most animals need freshwater to live. Only a small fraction of the world’s water is found in rivers and lakes. Section 2: Climate Main Idea Wind and water carry rainfall and the sun’s warmth around the world to create different climates. • Region Climate is the usual pattern of weather over a long period of time. • Region The Tropics, near the Equator, receive more of the sun’s warmth than other regions. • Location Landforms and position near water affect climate in a local area. • Culture Human actions like building cities, burning fuels, and clearing the rain forests can affect climate. Section 3: Climate Zones and Vegetation Main Idea Geographers divide the world into different climate zones. • Region The world has five main climate regions that are based on latitude, amount of moisture, and/or elevation. These regions are tropical, mid-latitude, high latitude, dry, and highland. • Region Each climate zone has particular kinds of vegetation Section 4: An Environmental Balance Main Idea People’s actions affect the environment. • Human/Environment Interaction A delicate balance exists among the earth’s hydrosphere, lithosphere, atmosphere, and biosphere. • Human/Environment Interaction People need to carefully manage and conserve water and land resources.