discussion of North America s physical features, including its landforms and bodies of

Transcription

1 Chapter 7 Natural Environments of North America Chapter 7 focuses on the natural environments of North America. The chapter opens with a discussion of North America s physical features, including its landforms and bodies of water. Next, the chapter examines the climates, plants, and animals that are found in North America. Chapter 7 closes with a discussion of North America s natural resources, including its farming, forests, and water resources and its energy and mineral resources. HRW/WGT Audio Summaries/Chapter 7/ page 1

2 Chapter 7 Section 1: Physical Features In this section you will learn what major landform regions are found in the United States and Canada. You will also learn about the bodies of water that are found in the region. HRW/WGT Audio Summaries/Chapter 7/ page 2

3 Chapter 7.1 Section Summary North America is a continent. The United States and Canada make up about 80 percent of this continent. The region has spectacular scenery. Landforms range from wide plains to high mountains, plateaus, and volcanoes. The landforms of the eastern half of the United States and Canada are older than those of the western half. Eastern mountains have been eroded, or worn away. Rolling hills and flatlands now cover most of the region. The western half has a younger landscape. Steep mountains, active volcanoes, deep canyons, and high plateaus are found there. A long coastal plain stretches along the Atlantic Ocean and Gulf of Mexico from New England to Mexico. This low plain lies close to sea level. It rises gradually inland. Barrier islands have formed along some parts of the coastal plain. Ocean waves and currents create these long, narrow islands by depositing sand in shallow water. The Piedmont is inland from the coastal plain. A piedmont is an area at or near the foot of a mountain region. The Piedmont stretches from New Jersey to Alabama. The boundary between the Piedmont and the coastal plain is called the fall line. Many early settlements formed along the fall line. This is because small ships could easily reach this natural boundary from the ocean but could not sail past it. The Appalachian Mountains are found to the west and north of the Piedmont. The Appalachians stretch from Alabama to southeastern Canada. The Blue Ridge, Catskill, and Green Mountains are mountain ranges in the Appalachians. North America s interior plains lie between the Appalachians and the Rocky Mountains. The Mississippi River and its tributaries drain most of this region. During the last ice age, glaciers covered the northern interior plains. Today there are thousands of lakes there, including the Great Lakes. The interior plains partly surround a highland region in Missouri, Arkansas, and Oklahoma. These interior highlands are a region of old eroded uplands. They include the Ozark Plateau. Farther west are the Great Plains. HRW/WGT Audio Summaries/Chapter 7/ page 3

4 The Canadian Shield lies north of the interior plains. The Canadian Shield is an arc of ancient rock that covers nearly half of Canada. It is centered on Hudson Bay. The Rocky Mountains stretch from New Mexico to Canada. West of the Rocky Mountains, or Rockies, lie the Cascade range and the Sierra Nevada. These two mountain ranges are located near the Pacific coast. The area between these ranges and the Rockies is called the intermountain region. Most of the intermountain region is made up of high plateaus with deep canyons, mountain ranges, and desert basins. A basin is a lower area of land, generally surrounded by mountains. The Great Basin makes up a large area of the U.S. intermountain region. California s Death Valley is located farther west, at the edge of the Great Basin. Death Valley contains the lowest point in North America. The Pacific coast region contains two major mountain ranges. They are the Sierra Nevada and the Cascade Range. High volcanoes are found in the Cascades. These volcanoes include Mount Ranier, Mount Hood, Mount Shasta, and Mount St. Helens. The Pacific coast region also has three fertile valleys. These are the Puget Sound lowland in Washington, the Willamette River valley in Oregon, and the Central Valley in California. The western United States is part of the Ring of Fire. This is a tectonically active region around the edges of the Pacific. It has many active volcanoes and earthquake faults. Alaska and Hawaii are the two westernmost U.S. states. They are geologically active, too. The Hawaiian Islands are the tops of underwater volcanoes that rise from the ocean floor. They formed over a hot spot. A hot spot is a place where magma wells up to the surface from Earth s mantle. Alaska s southern coast is a subduction zone. Powerful earthquakes sometimes occur there. The crest, or high point, of the Rockies marks the Continental Divide. This crest divides North America s major river systems into those flowing eastward and those flowing westward. To the east, the Mississippi, Missouri, and Ohio Rivers make up the continent s major river system. This system drains most of the U.S. interior plains. The second major river system in the interior plains is the St. Lawrence system. The St. Louis HRW/WGT Audio Summaries/Chapter 7/ page 4

5 connects the Great Lakes to the Atlantic Ocean. It drains most of southeastern Canada. In northwestern Canada, the Mackenzie River system drains the interior plains. It also drains part of the Canadian Shield. Three large northern lakes drain into the Mackenzie. These lakes are Lake Athabasca, Great Slave Lake, and Great Bear Lake. The Colorado, Columbia, Fraser, and Yukon Rivers flow west out of the Rockies. The Columbia and Fraser flow into the Pacific Ocean. The Colorado flows into the Gulf of California. The Yukon River flows across Alaska to the Bering Sea. North America has many lakes. In fact, it has more large lakes than any other continent. Most of these lakes were created by continental ice sheets during the ice ages. HRW/WGT Audio Summaries/Chapter 7/ page 5