Landforms, Rivers and Climate Regions of the United States

Look around a landscape. Some parts rise, some dip, and others stretch out flat. Each natural shape of Earth's surface is a landform.

High land and low land

A mountain rises high above nearby land, usually with steep sides. Its top is a peak. A hill is lower and gentler. A plain is wide, flat or gently rolling land. A plateau is high, mostly flat land with at least one steep side. A plain can also be high: the western Great Plains rise above 5,000 feet (about 1,500 m).

A valley is low land between hills or mountains. Rivers often flow through valleys. A canyon is a deep, narrow valley with steep rock walls. A river can carve one over a very long time. Arizona's Grand Canyon is a famous example. A basin is a low area surrounded by higher land. Some basins hold lakes.

Picture this clue: "The land rises above its surroundings. Its top is broad and flat, with steep cliffs along the edge." First, notice the raised land. Next, notice its flat top and steep edge. Together, these clues describe a plateau. A mountain peak would not have that broad, flat top.

Where land meets water

The coast is where land meets a sea or ocean. Florida is a peninsula: water borders three sides, but one side joins the mainland. An island, such as an island of Hawaii, has water all around it. A bridge can join an island to other land without changing its natural shape.

A bay is water reaching into the land, such as Chesapeake Bay. A gulf is a very large bay. South of the United States lies the Gulf of America, also called the Gulf of Mexico.

Water on the map

An ocean is a huge body of salt water. The Atlantic lies east of the United States. The Pacific lies west, and the Arctic Ocean borders northern Alaska. A lake has land all around it. Most lakes contain fresh water, but Utah's Great Salt Lake is salty. A river flows downhill through a long channel.

These words help you picture place names. The Colorado Plateau suggests high, flat land. California's Central Valley suggests lower land between higher areas. The names give you a starting picture; a physical map adds the details.

A map can show mountain heights without drawing a mountain sideways. It uses colors, symbols, and numbers to show elevation: height above sea level.

Start at the sea

Sea level is the height of the ocean's surface. It is the starting height, 0 feet. A place can lie below it. Badwater Basin in California is 282 feet (86 m) below sea level. You may see its elevation written as −282 feet. The minus sign means "below," not a mountain pointing downward.

A physical map shows natural features, such as rivers and mountains. A political map shows states, borders, capitals, and cities. Many maps show both kinds of information.

Read colors before using them

Always read the map key, also called the legend. Many elevation maps use green for low land. Yellow, tan, and brown often show higher land. Purple or white may mark the highest areas. Different maps use different colors.

Green on an elevation map tells you height. It does not tell you whether trees grow there. A low desert can be green on the map. A high forest can be brown. Blue lines usually show rivers; blue shapes show lakes. A triangle often marks a peak, with its height beside it. Shaded relief, which looks like shadows, helps you spot rough mountain slopes.

Compare the extremes

Denali in Alaska, officially called Mount McKinley by the US government, reaches 20,310 feet (6,190 m). It is North America's highest point. Mount Whitney in California reaches 14,505 feet (4,421 m). It is highest in the 48 contiguous states: the connected states between Canada and Mexico. Badwater Basin is North America's lowest point.

How much higher is Whitney than Badwater? Travel up 282 feet from Badwater to sea level. Then travel up another 14,505 feet to Whitney.

The height difference is 14,787 feet (about 4,507 m). Adding is right because the trip crosses sea level. The places are less than 100 miles (160 km) apart.

Picture the country sideways

From the Atlantic, the low Coastal Plain rises into the Appalachians. Their highest peak reaches 6,684 feet (2,037 m). The land drops into the Interior Lowlands, then climbs gently across the Great Plains. Denver stands at 5,280 feet (1,609 m). Next come Rocky Mountain peaks above 14,000 feet (about 4,270 m), high basins, and Pacific mountain ranges. Low valleys lead toward the Pacific shore. Overall, the West is higher than the East.

Start at the Atlantic shore and head inland. The ground rises in stages: first the Coastal Plain, then the Piedmont hills, then the Appalachian Mountains.

Low land beside the sea

The Coastal Plain follows the Atlantic Ocean and the Gulf of America (also called the Gulf of Mexico). It is narrow in New England and wider farther south. All of Florida and the Texas coast belong to it. Most of this land is below 500 feet (150 m).

You will find beaches, bays, marshes, and swamps here. Barrier islands are long, thin sandy islands near the shore. North Carolina's Outer Banks are an example. Chesapeake Bay reaches far inland. Southern Florida's Everglades is a huge, slow-moving wetland, often called a "river of grass." Near the coast, river mouths and sheltered bays offer places for harbors.

Rivers tumble at the fall line

The Piedmont is rolling land between the plain and the mountains. Its name means "foot of the mountains." Its harder rock meets the Coastal Plain's softer sand and clay at the fall line. Rivers crossing this boundary tumble through waterfalls and rapids.

Imagine a ship bringing goods upriver from the ocean. At the rapids, it cannot continue. Workers unload the cargo there. Nearby, falling water can turn a mill wheel. Those two advantages helped towns grow. Richmond, on the James River, and Washington, D.C., on the Potomac, are fall-line cities.

Old mountains with rounded tops

The Appalachians run northeast from Alabama and Georgia through Maine and into Canada. The Blue Ridge, Great Smoky, Green, and White Mountains are smaller ranges within this chain. Forests cover much of the land. Long ridges stand beside narrow valleys. Coal lies beneath parts of West Virginia, Kentucky, and Pennsylvania.

The Appalachians formed hundreds of millions of years ago. Water, ice, and wind have worn them down for a long time. Their peaks are generally lower and rounder than the younger Rockies. Low mountains can be very old. Their shape tells a story of wearing away.

Mount Mitchell in North Carolina is the highest Appalachian peak. At 6,684 feet (2,037 m), it is highest east of the Mississippi. California's Mount Whitney is more than twice as high.

Long ridges made westward travel difficult for early settlers. Travelers searched for passes, low gaps through mountains. The Cumberland Gap, where Kentucky, Tennessee, and Virginia meet, provided an important route.

A huge stretch of plains lies between the Appalachians and the Rockies. Together, these are the Interior Plains. Their eastern and western parts have different heights and amounts of rain.

The lower, wetter part

The Interior Lowlands, also called the Central Plains or Central Lowlands, include much of Ohio, Indiana, Illinois, Iowa, and Missouri. Their land is flat or gently rolling. Elevations range from a few hundred feet to about 1,500 feet (460 m). The Mississippi, Missouri, and Ohio Rivers cross this region.

During the Ice Age, thick, moving sheets of ice called glaciers covered the northern lowlands. They scraped and flattened the land. They left soil and rock behind and deepened basins that now hold the Great Lakes. Rich soil and enough rain help farmers grow corn and soybeans.

The higher, drier part

The Great Plains stretch from Texas north through Oklahoma, Kansas, Nebraska, the Dakotas, and Montana into Canada. They reach west to the foot of the Rockies. Much of the land is grassland. Trees grow mainly where extra water is available, such as along rivers. Huge bison herds once grazed here. Wheat farms, cattle ranches, and wind turbines are common today.

A gentle climb can add up

Kansas can look flat while you travel across it. Yet its low point in the east is 679 feet (207 m). Mount Sunflower near its western border is 4,039 feet (1,231 m).

That is a height difference of 3,360 feet (about 1,024 m). The rise happens across a wide distance, so you may hardly notice it. Farther west, Denver sits at 5,280 feet (1,609 m), one mile above sea level.

"Plain" does not mean perfectly flat everywhere. The Great Plains also have hills, river valleys, the rocky Badlands, and South Dakota's Black Hills. They remain a plains region because broad, fairly flat land is the main pattern.

The open land also lets cold air from the north meet warm, wet air from the south. That helps explain the region's tornadoes. Its dry spells and strong winds help explain another event you will study: the Dust Bowl.

The Rockies rise above the western edge of the Great Plains. Beyond them, high plateaus and dry basins stretch toward the Pacific mountains.

High ridges and low passes

The Rocky Mountains run about 3,000 miles (4,800 km), from New Mexico through the western states and into Canada. They are the largest mountain system in the lower 48. They are much younger than the Appalachians, with tall, sharp peaks. Many exceed 14,000 feet (4,270 m). Mount Elbert in Colorado is their highest peak: 14,440 feet (4,401 m).

Snow covers high peaks for much of the year. Glaciers carved many deep valleys. The Continental Divide follows high ridges. Water falling on opposite sides begins different downhill journeys. Much of the east-side water reaches the Mississippi system. West-side water heads toward the Pacific or stays inside the Great Basin.

People crossed these mountains through passes. On the Oregon Trail, wagon travelers used South Pass in Wyoming. A low gap made crossing easier than climbing a high peak.

A river cuts a plateau

The Colorado Plateau spreads across parts of Utah, Arizona, Colorado, and New Mexico. It is high land cut by deep canyons. Over millions of years, the Colorado River carved the Grand Canyon in Arizona. The canyon is about 277 miles (446 km) long, up to 18 miles (29 km) wide, and about a mile (1.6 km) deep. A plateau's broad surface can remain high while a river cuts far below it.

Water stays in the Great Basin

The Great Basin covers most of Nevada and western Utah. Rows of short mountain ranges separate flatter valleys. Its streams have no route to the ocean. Water ends in lakes, soaks into the ground, or evaporates into the air.

The Great Salt Lake is the region's largest lake. Streams bring in water and small amounts of dissolved salt. Water evaporates, but salt stays behind. With no river carrying salt out, the lake becomes much saltier than the ocean. It is a remnant of a much larger Ice Age lake.

Dry does not always mean hot

A desert gets very little rain or snow. The Great Basin Desert has cold, snowy winters. Much of its ground has rock, gravel, and sagebrush. Sand dunes are only one desert feature.

The Mojave Desert includes Death Valley. Badwater Basin there is 282 feet (86 m) below sea level. Death Valley also holds the recorded world air-temperature high: 134°F (56.7°C), measured July 10, 1913.

The Pacific side has several mountain ranges with lower land between them. Alaska adds enormous mountains and glaciers. Hawaii adds islands built by volcanoes.

Ranges and valleys of the West Coast

The Coast Ranges stand near the Pacific. Farther inland, the Sierra Nevada rises in California. The Cascade Range runs from northern California through Oregon and Washington.

The Sierra Nevada has granite peaks and deep valleys, including Yosemite Valley. Mount Whitney reaches 14,505 feet (4,421 m), highest in the lower 48. Winter snow stores water in the mountains. As it melts in spring and summer, rivers carry water to farms and cities.

The Cascades include volcanoes such as Mount Rainier, Mount Hood, and Lassen Peak. Rainier, at 14,410 feet (4,392 m), is the range's highest peak. On May 18, 1980, Mount St. Helens erupted and blew away its top.

California's Central Valley lies between the Coast Ranges and Sierra Nevada. Rich soil and water help make it a major farming area. Oregon's Willamette Valley and Washington's Puget Sound lowland are other important low areas. Seattle stands beside Puget Sound.

Alaska's giant landscapes

Alaska is more than twice the size of Texas. The Alaska Range holds Denali, officially Mount McKinley, at 20,310 feet (6,190 m). It is North America's highest mountain. The Brooks Range crosses northern Alaska. Farther north, the flat, treeless North Slope borders the Arctic Ocean. The Yukon River crosses the state's middle. Glaciers fill many valleys, and volcanoes line the Aleutian Islands.

Islands rising from the sea

Hawaii lies more than 2,000 miles (3,200 km) from the mainland. Volcanoes rose from the ocean floor to build all eight main islands. The largest island, Hawaiʻi, is also called the Big Island. Mauna Loa and Kīlauea are active volcanoes there. Mauna Kea rises almost 14,000 feet (about 4,200 m) above sea level.

Compare peaks carefully

The tallest US mountain is in Alaska. The tallest in the lower 48 is in the Sierra Nevada. Even the highest Rocky Mountain peak is slightly lower than Whitney:

Whitney is 65 feet (about 20 m) higher than Elbert.

Volcanoes also occur outside Hawaii. The Cascades have many, and Alaska has more active volcanoes than any other state. Pacific mountain ranges also shape rainfall: ocean-facing slopes receive wet air, while land behind the ranges can be dry.

Imagine rain landing on a hillside. It runs downhill into a stream. That stream joins a river. The land's slopes guide every part of the journey.

Name the parts of a river

A river's source is where it begins. It might start at a spring, a lake, or melting mountain snow. Its mouth is where it enters another river, a lake, or the sea. A tributary flows into a larger river. A main river and all its tributaries form a river system.

Upstream means toward the source. Downstream means toward the mouth. Tributaries add water as they join, so the main river generally grows bigger downstream.

Water flows downhill because gravity pulls it toward lower land. South on a map is not always downhill. Florida's St. Johns River flows north. The Red River of the North flows north into Canada. The Columbia flows west, and the Ohio flows southwest. Check the land's heights and the river's source and mouth.

The land that feeds a river

A watershed, or drainage basin, is all the land draining into the same river. It includes fields and hills far from the riverbank. A ridge called a divide separates one watershed from another. Rain falling on different sides runs in different directions.

The Continental Divide follows high Rocky Mountain ridges. Much of the east-side water reaches the Gulf of America (also called the Gulf of Mexico) and the Atlantic. Much of the west-side water heads toward the Pacific. Some drains into the closed Great Basin.

Follow two raindrops

One drop lands in Colorado on a slope feeding the South Platte. Follow its route:

1. South Platte River to the Platte River in Nebraska.
2. Platte River to the Missouri River.
3. Missouri River to the Mississippi River.
4. Mississippi River to the Gulf.

Another drop lands on a nearby slope feeding the Colorado River. It heads southwest through the Grand Canyon toward the Gulf of California, part of the Pacific. A short distance across a ridge can lead toward a different ocean.

Rivers carve and build

Moving water wears away rock and carries sand and mud. Over a very long time, it can carve valleys and canyons. Near some river mouths, slower water drops its load. The sand and mud build new land called a delta. The Mississippi Delta spreads into the Gulf.

A floodplain is flatter land beside a river that can flood. Floodwater can leave rich soil there when it drains away. That helps farming, but buildings on floodplains face flood danger.

The Mississippi river system links mountain slopes, farms, and cities across a huge part of the country. On a map, picture the Mississippi as a tree trunk and its tributaries as branches.

Start in Minnesota

The Mississippi River begins at Lake Itasca in northern Minnesota. It starts as a small stream. It flows south about 2,350 miles (3,780 km), past Minneapolis, St. Louis, Memphis, and New Orleans. Its mouth opens into the Gulf of America (also called the Gulf of Mexico). The river begins far north of the state named Mississippi.

The Missouri River starts in Montana's Rocky Mountains. It flows east and south across the Great Plains. It joins the Mississippi just north of St. Louis. At about 2,540 miles (4,090 km), the Missouri is slightly longer than the Mississippi. River lengths vary a little as channels bend and change.

The Ohio River begins at Pittsburgh. There, the Allegheny and Monongahela Rivers join. The Ohio flows southwest to meet the Mississippi at Cairo, Illinois. The Arkansas, Red, Tennessee, and Illinois Rivers are other important parts of the system. Some join through another tributary before their water reaches the Mississippi.

A watershed reaching from range to range

The system drains about 41 percent of the 48 contiguous states. Its watershed includes all or part of 31 states and two Canadian provinces. It reaches from the Rockies in the west to the Appalachians in the east. Rain falling far from the main river can eventually join it.

Trace a downstream trip

A barge leaves Pittsburgh carrying heavy goods toward the Gulf.

1. It follows the Ohio southwest.
2. At Cairo, it enters the Mississippi.
3. It heads south past Memphis.
4. It passes New Orleans and continues through the delta toward the Gulf.

The trip goes downstream throughout. The barge never needs to enter the Missouri. That river joins the Mississippi farther upstream.

A water highway

Barges carry grain, coal, and other heavy goods. On the upper Mississippi, locks and dams help boats pass changes in water height. A lock is a chamber with gates. Water rises or falls inside it to lift or lower a boat, like a water staircase.

The Mississippi also separates parts of neighboring states. Iowa and Illinois face each other across it; so do Arkansas and Tennessee. You may hear people describe places as "east of the Mississippi" or "west of the Mississippi." The river helps people describe the country's broad geography.

A river's name, source, and mouth help you trace its place in the country. These five rivers connect very different landscapes.

Two rivers starting in Colorado

The Colorado River begins west of the Continental Divide. It flows southwest through Utah and Arizona and carves the Grand Canyon. Hoover Dam, between Nevada and Arizona, holds back water to make Lake Mead. The river heads toward Mexico's Gulf of California, on the Pacific side. Farms and cities in seven US states and Mexico use so much water that the river often runs dry before reaching the sea.

The Rio Grande begins east of the Divide in Colorado. It flows south through New Mexico, then forms the border between Texas and Mexico. It reaches the Gulf of America (also called the Gulf of Mexico), on the Atlantic side. Its Spanish name means "big river."

Compare the two sources. Both are in Colorado's mountains. Their positions on opposite sides of the Divide explain their different routes toward the sea.

A powerful Pacific river

The Columbia River begins in Canada's Rocky Mountains. It crosses Washington, then forms much of the Washington–Oregon border. It empties into the Pacific Ocean. Grand Coulee Dam uses its flowing water to generate electricity. Salmon swim upriver from the ocean to lay eggs. Lewis and Clark followed the Columbia to the Pacific in 1805.

Rivers in New York and Alaska

The Hudson River flows south from New York's Adirondack Mountains. It reaches New York Harbor and the Atlantic Ocean. The Yukon River starts in Canada and flows west across Alaska. Its mouth is on the Bering Sea.

A dam changes the journey

A dam holds water in a reservoir, a stored lake. Water can pass through gates and machines and continue downstream. A dam does not normally block all water forever. It can store drinking water, supply farms, and make electricity.

Some rivers form borders as well as routes. The Columbia separates parts of Washington and Oregon. The Rio Grande separates Texas and Mexico. To read a river map, follow the water line; a border line alone does not tell you which way the river flows.

The five Great Lakes look almost like inland seas. They hold fresh water and connect the middle of North America with the Atlantic Ocean.

Learn their names and compare them

From west toward east, remember Superior, Michigan, Huron, Erie, Ontario. Lake Ontario is officially called Lake America in US federal use. The word HOMES helps recall all five names: Huron, Ontario, Michigan, Erie, Superior. HOMES is a name reminder, not their geographic order.

Four lakes lie along the US–Canada border. Michigan is the only one entirely inside the United States. It touches Michigan, Wisconsin, Illinois, and Indiana. The other lakes also reach Minnesota, Ohio, Pennsylvania, and New York: eight US states in all.

Together, they hold about 84 percent of North America's fresh surface water and 21 percent of the world's. Their combined area is about 94,000 square miles (244,000 km²). This counts fresh water at the surface, not all water underground or frozen in ice.

Superior covers about 31,700 square miles (82,100 km²). Huron covers about 23,000 square miles (59,600 km²), Michigan 22,300 (57,800 km²), and Ontario 7,340 (19,000 km²). To compare Superior with Ontario, divide their areas:

Superior has more than four times Ontario's area.

Follow the water, including the branch

Superior drains through the St. Marys River into Huron. Michigan joins Huron at the Straits of Mackinac. Water does not flow from Superior through Michigan as one long chain. From Huron, connected rivers lead past Detroit into Erie. The Niagara River carries Erie's water over Niagara Falls into Ontario. Ontario drains through the St. Lawrence River toward the Atlantic.

Ice, ships, and snow

Ice Age glaciers dug and deepened the lake basins. Meltwater filled them. Ships now travel through connected waterways and locks between the Atlantic and Duluth on Lake Superior. Chicago, Detroit, Cleveland, Milwaukee, and Buffalo grew along these routes.

In winter, cold air crossing the lakes picks up moisture. It can drop heavy lake-effect snow downwind, including near Buffalo. A lake can shape the weather of land beside it.

"It is rainy and 55°F (13°C) in Chicago today" describes weather. Weather is what the air is like at one time and place. Climate is the usual weather pattern over many years, often measured over 30 years. Chicago's cold winters and warm summers describe its climate. One snowy day cannot tell you a place's usual winter pattern.

Four clues to climate

Distance from the equator: places closer to the equator receive more direct sunlight. Hawaii and southern Florida stay warm all year. Farther north, Minnesota and Alaska have colder winters.

Elevation: air gets cooler as you climb higher. A mountain can keep snow when nearby low ground is warm. Mauna Kea in tropical Hawaii sometimes has snow on top.

Oceans: water warms and cools more slowly than land. Near the coast, it softens summer heat and winter cold. Far inland, summers can be hotter and winters colder.

Mountains: wet ocean air rises over a range. As it cools, rain or snow falls on the wind-facing side. Less moisture remains when the air crosses the ridge. The dry land behind the range lies in a rain shadow.

Compare two sides of a range

Seattle is west of the Cascades. It receives about 39 inches (1,000 mm) of water from rain and melted snow in a normal year. Yakima, east of the range, gets about 8 inches (200 mm).

Seattle gets about five times as much. Wet air meets the western slopes first. Yakima lies in the rain shadow. Hawaii also has rainy wind-facing slopes and drier sheltered sides.

Put clues together

To describe eastern Washington, first check location: it is fairly far north. Next, notice that it is inland, beyond the Cascades. Those clues help explain cold winters, hot summers, and dry conditions.

Location north or south is only one clue. Flagstaff, Arizona, is farther south than San Francisco. Yet Flagstaff has much colder, snowy winters. It is almost 7,000 feet (2,100 m) high and inland. San Francisco lies near sea level beside the Pacific.

Read the plants

Vegetation means the plants growing naturally in a place. Enough rain supports forests in much of the East and Pacific Northwest. Drier plains support grasses. Very dry places have shrubs and some cacti. Bitterly cold places support low tundra plants. The mix of warmth and water helps explain what you see.

A cool climate can mean a treeless Arctic plain, a snowy farm region, or a rainy coast. Compare both temperature and plants to tell these places apart.

Northern and interior Alaska

Northern Alaska has an Arctic, or tundra, climate. Winters are long and bitterly cold; summers are short and cool. In the far north, the sun stays below the horizon for weeks in winter. It stays above it for weeks in summer. Mosses, grasses, and small shrubs grow, but trees do not.

Much of the ground beneath tundra is permafrost. It stays frozen for at least two years in a row. Only a top layer thaws during summer. Frozen ground below stops water soaking deeply in, leaving soggy ground and ponds.

Interior Alaska has a subarctic climate. Winters are very long and cold. Summers are short but can be warm. Fairbanks can have summer days above 80°F (27°C). Spruce and birch forests grow here. Prospect Creek recorded −80°F (about −62°C) on January 23, 1971, the lowest recorded US temperature.

Four seasons across the northern states

Much of the northern Great Plains, Midwest, and New England has a cold-winter climate, also called humid continental. Winters are cold and snowy. Summers are warm or hot. Rainfall supports forests and farms. Unlike tundra, this region has enough summer warmth for trees.

A mild, wet Pacific coast

Western Washington and Oregon have a marine climate. The ocean keeps winters mild and summers cool. Rain is frequent from fall through spring; summers are drier. Tall evergreen forests grow here. Washington's Hoh Rain Forest is a temperate rain forest: a rainy forest in a mild climate. Southeastern Alaska's coast has a similar climate.

Alaska's southern coast has milder winters than its interior. The ocean matters there too. Alaska has several climates, so one picture of ice cannot describe the whole state.

Climb above the trees

The Rockies, Sierra Nevada, Cascades, and Alaska's mountains have highland climates. Higher slopes are colder and snowier. Above the tree line, cold and wind prevent trees from growing. Low plants can still grow there.

Mountain snow is also stored river water. When it melts, it feeds rivers such as the Missouri and Colorado. A snowy mountain far away can help supply water to a warm valley.

Two places can both feel hot in July yet have different climates. Look at winter temperatures and when rain falls, as well as summer heat.

Warm places with plenty of moisture

Most of the Southeast has a humid subtropical climate. Summers are long, hot, and sticky. Thunderstorms are common, and rain falls throughout the year. Winters are mild but can have freezing nights. Pine forests grow well. The long growing season suits cotton, peanuts, and rice.

Hawaii's lowlands and the southern tip of Florida have a tropical climate. Every month's average temperature stays above about 64°F (18°C). Wetter and drier seasons take the place of a cold winter. Miami, the Everglades, and the Florida Keys are examples. High Hawaiian mountains are much colder than the lowlands. Puerto Rico and other US territories are tropical too.

Dry summer or dry all year?

Coastal and central California have a Mediterranean climate. Most rain falls in winter. Rivers and canals supply summer water for farms growing almonds, oranges, grapes, and vegetables.

Much of the western Great Plains and parts of the West are semi-arid. They receive enough water for short grasses, but few trees. Strong winds and droughts, long dry spells, are common. The eastern plains get more rain and share the wetter climates farther east.

A useful desert rule is less than about 10 inches (250 mm) of water from rain and melted snow yearly. The Mojave and Sonoran are hot deserts. Giant saguaro cacti grow in the Sonoran. The Great Basin is a cold desert with snowy winters.

Match a whole-year pattern

"Warm every month on a Pacific island" points to tropical lowlands. "Dry summers and mild, rainy winters on California's coast" points to Mediterranean climate. Most of the South has winter cold that tropical places lack. One state can also contain several climates: California has rainy coasts, dry valleys, snowy mountains, and deserts.

US records range from −80°F (−62.2°C) at Prospect Creek, Alaska, to 134°F (56.7°C) in Death Valley. From −80 to 0 is 80 degrees; from 0 to 134 is another 134.

The records differ by 214 Fahrenheit degrees.

A natural hazard is an event in nature that can harm people or buildings. It becomes a disaster when it causes great harm. The land and climate help explain where different hazards occur.

Two spinning storms

A hurricane has winds of at least 74 miles per hour (119 km/h). The Atlantic and Hawaii hurricane seasons run from June 1 through November 30. Many storms occur in late summer and early fall. Gulf and Atlantic coasts, including Florida, Texas, Louisiana, and the Carolinas, face hurricane danger. Hawaii can be struck too.

Hurricane winds damage buildings. Heavy rain floods inland places. Storm surge is ocean water pushed onto land by the storm. In 2005, Hurricane Katrina's surge overwhelmed flood defenses and helped flood much of New Orleans.

A tornado is a violently spinning column joining a thunderstorm to the ground. Most form over land, but they can also occur over water. The United States has about 1,200 yearly, more than any other country. Many occur in spring and early summer. Tornado Alley includes parts of Texas, Oklahoma, Kansas, and Nebraska. Cold, dry air from the north can meet warm, wet air from the Gulf of America (also called the Gulf of Mexico). The Southeast also has many tornadoes. Hurricanes can produce tornadoes as they move inland.

Water on normally dry land

A flood covers land that is usually dry. Floods are the country's most common natural hazard and can occur in every state. Heavy rain or melting snow can overfill a river. The Mississippi had major floods in 1927 and 1993. Storm surge causes coastal flooding.

A flash flood rises within minutes or a few hours. A dry canyon can suddenly fill after a heavy storm. Dry ground or hard surfaces may absorb water slowly, and steep slopes send runoff into narrow channels. A desert's usual dryness does not prevent a sudden flood.

Use the setting

Compare three places. A Louisiana coastal town faces hurricanes, surge, and flooding. An Oklahoma plains farm faces tornadoes. A city beside the Mississippi faces river floods.

Some hazards begin beneath your feet. Others spread through dry plants. Their causes explain why they are common in different places.

Moving rock makes the ground shake

Earth's outer layer is broken into huge, slowly moving plates. A fault is a crack where rock can move. When rock suddenly slips, the ground shakes in an earthquake. Many earthquakes occur near plate edges.

The Pacific Coast and Alaska lie along the Ring of Fire, a belt of earthquakes and volcanoes around the Pacific's edges. California's San Andreas Fault marks plates sliding past each other. Alaska has the most earthquakes of any state. California has the most damaging ones.

Hawaii lies in the middle of a plate. A very hot place deep inside Earth, called a hot spot, feeds its volcanoes and helps explain its earthquakes.

The San Francisco earthquake struck in 1906. On March 27, 1964, Alaska had a magnitude 9.2 earthquake, the strongest recorded in the United States. The New Madrid earthquakes of 1811–1812, centered in Missouri, show that strong shaking also happens far from the Pacific. Scientists can identify areas of danger, but cannot predict an earthquake's exact day or hour.

Melted rock and ocean waves

A volcano is an opening where melted rock, gas, and ash erupt. Underground melted rock is magma. At the surface, it is lava. The Cascades, Alaska, and Hawaii have volcanoes. Mount St. Helens erupted in 1980, and Kīlauea erupts often.

An undersea earthquake can move water and cause a tsunami, a series of powerful waves. Alaska, Hawaii, and the West Coast face this coastal hazard.

Dry plants help fire spread

A wildfire is an unplanned fire in forests, grass, or brush. It needs fuel, heat, and air. Dry plants provide fuel. Hot, dry weather and strong winds help flames spread quickly. Fires occur nationwide; the South has many each year. Many of the largest burn in the dry West.

People start most US wildfires, through campfires, equipment sparks, and other actions. Lightning starts others. Southern California's hot, dry Santa Ana winds can drive flames quickly, as in the Los Angeles fires of January 2025.

Fire also helps some plants reproduce. Heat can open giant sequoia cones and release seeds. Forest managers sometimes use carefully planned prescribed burns to reduce dry fuel. These planned fires differ from uncontrolled wildfires.

A hazard map shows where a danger is more likely. Start with its key, just as you do with a physical map. A darker color may mean higher risk. Compare the two maps to connect the hazard with the land.

Match places and hazards

• Gulf and Atlantic coasts: hurricanes, storm surge, and floods.
• Great Plains and Southeast: tornadoes and floods.
• Big river valleys: river floods.
• West Coast and Alaska: earthquakes, volcanoes, and tsunamis.
• Dry West: large wildfires, droughts, and flash floods.
• Hawaii: volcanoes, hurricanes, and tsunamis.

These are main patterns. No region is free of every hazard. A pale color on one hazard map does not describe every kind of danger.

Watch or warning?

A watch means dangerous conditions are possible in your area. Get ready and follow updates. A warning means dangerous conditions are expected or already happening. Take the recommended safety steps now.

For example, "Tornado Watch" means your family should be ready to use its plan. "Tornado Warning for your county" means move to the safe place right away.

Use the right safety action

• Tornado: go to a basement or small, windowless room on the lowest floor. Cover your head. A highway overpass is not a safe shelter.
• Earthquake: Drop, Cover, and Hold On. Drop to hands and knees, get under a sturdy table, and hold on. Running outside can put you beneath falling glass or bricks.
• Flood: stay out of floodwater on foot and in vehicles. Turn Around, Don't Drown. Just 6 inches (15 cm) of fast-moving water can knock an adult down.
• Hurricane or wildfire evacuation: leave with your family when officials tell you to leave.

Prepare before an event

Families make plans for where to go and how to find each other. An emergency kit includes drinking water, food that keeps, a flashlight, batteries, first-aid supplies, and medicines.

Communities also prepare. Levees and floodwalls hold back river water. Raised homes help keep living areas above coastal floods. Buildings designed to sway can better withstand shaking. Tornado shelters and sirens help plains communities. Firebreaks, cleared strips of land, help slow fires.

Imagine moving from Oklahoma City to Los Angeles. The old plan emphasized tornado shelter and flood alerts. The new plan also needs earthquake practice, secure bookshelves, and wildfire escape routes. A change of place can change what a family prepares for.

Think about a wooden desk, a glass of water, or electricity from wind. Each depends on a natural resource, something from nature that people use.

Can nature replace it?

A renewable resource can be replaced within a human lifetime when people use it carefully. Trees can regrow, and fish can reproduce. Water is renewed through nature's movement of water. Sunlight and wind keep supplying energy.

Nonrenewable resources cannot be replaced on a human timescale. Coal, oil, and natural gas take millions of years to form. Metal ores are limited deposits too. Recycling metal saves material, but does not create new ore in the ground.

Renewable does not mean endless. Cutting trees or catching fish faster than they recover can use them up locally. Conservation means using resources wisely. Replanting trees, limiting catches, and recycling help protect supplies.

Match resources with regions

Wyoming mines more coal than any other state. Texas leads oil production and wind electricity generation. Oil and natural gas also come from the Gulf, Alaska's North Slope, North Dakota, and New Mexico. Minnesota leads iron-ore mining, Arizona copper, and Nevada gold.

Rivers and lakes supply drinking water, water for farms, and shipping routes. Falling water at Grand Coulee Dam on the Columbia and Hoover Dam on the Colorado makes hydroelectric power. Wind turbines use the plains' strong winds. Sunny southwestern deserts suit solar power.

Alaska leads the states in fish catch, including salmon and pollock. Gulf waters supply shrimp, Chesapeake Bay blue crabs, and Maine lobster.

Read a resource map

First read the symbol in the key: perhaps a wheat stalk. Next find where it appears often. Wheat symbols cluster on the Great Plains. Finally connect the pattern with the setting. Broad land and limited rain suit wheat and grasslands. A cluster of tree symbols in the Pacific Northwest connects with its wet climate. The map shows where a resource is; the land and climate help you explain why.

People need fresh water, food, places to build, and ways to travel. Land and water help explain where communities grew. People also made choices that changed those places.

Native nations used local resources

Native American nations lived across these regions for thousands of years before Europeans arrived. They are living peoples today, with homes and communities across the country.

Near the Great Lakes, Haudenosaunee families built longhouses using wood and bark. They grew corn, beans, and squash. Many Lakota people on the Plains followed bison herds and used movable tipis. Tlingit people in the Pacific Northwest fished for salmon and built cedar-plank houses. Hopi people in the dry Southwest built with stone and adobe, earth dried into building material. They farmed corn while carefully managing water. Different resources supported different ways of living.

Ships reached coastal settlements

European colonists arrived by sea. Atlantic river mouths and sheltered harbors offered landing places and trade routes. Jamestown was founded on Virginia's James River in 1607. Boston, New York, and Charleston grew as ports where ships could load and unload.

At the fall line, waterfalls and rapids stopped ships traveling upriver. Cargo had to move between boats and land routes. Falling water also powered mills. Richmond and Washington, D.C., grew near this boundary.

Gaps and river junctions

The Appalachians slowed travel west. Passes offered lower routes. In 1775, Daniel Boone helped mark the Wilderness Road through the Cumberland Gap into Kentucky.

Before railroads, river routes often moved heavy goods more easily than roads. Pittsburgh grew where the Allegheny and Monongahela join to form the Ohio. St. Louis grew near the Missouri–Mississippi junction. New Orleans grew near the Mississippi's mouth.

To explain St. Louis, first locate the rivers. Next identify the advantages: connected waterways, nearby farmland, and land for building. Then connect them to people. Traders could bring goods along the Mississippi, and travelers heading west could continue up the Missouri.

People built new connections

The Erie Canal opened in 1825. It connected the Hudson at Albany with Lake Erie at Buffalo. Boats could move goods between the Atlantic route and the Great Lakes more cheaply. New York City became the busiest US port, while Buffalo, Cleveland, and Chicago also grew.

Geography offered advantages, but did not decide every town's future. Laws, conflicts, choices, and technology mattered too. Railroads later helped cities such as Chicago and Denver grow.

Water, land, and minerals drew many settlers west. New tools helped them build farms and cities. These changes also harmed Native nations and sometimes damaged the soil.

Farms and routes across the plains

The Homestead Act of 1862 offered eligible settlers up to 160 acres (about 65 hectares) of public land. They had to live on and farm it for five years. With few trees available, some plains families built sod houses from blocks of grassy earth. Windmills pumped underground water. Steel plows cut thick prairie soil, and railroads carried people and crops.

The land was already home to Plains nations. Settlers took Native land, and hunters nearly wiped out the great bison herds. Native communities lost land and resources they depended on.

Wagon trails used mountain passes. During the 1840s, travelers on the Oregon Trail crossed South Pass in Wyoming toward Oregon's Willamette Valley.

Minerals and water drew people

Gold was discovered at Sutter's Mill in January 1848. In 1849, tens of thousands of "forty-niners" rushed to California. San Francisco grew quickly. Gold and silver discoveries also drew people into Rocky Mountain mining towns.

In dry country, settlements formed near available water. Salt Lake City grew near streams flowing from mountains. Las Vegas grew around desert springs; its name means "the meadows." Much of the Great Basin still has few people because water is scarce.

Technology brought new possibilities

Hoover Dam, completed in 1936, created Lake Mead on the Colorado River. Dams, canals, and aqueducts, channels carrying water, supplied cities and farms. Colorado River water serves Las Vegas, Phoenix, and Los Angeles. Irrigation helped California's Central Valley produce many crops.

Air conditioning became common in homes during the second half of the 1900s. It made hot cities more comfortable and helped places such as Phoenix and Houston grow.

Los Angeles combines a mild Mediterranean climate, land between mountains and sea, a port, and water brought from far away. Central Nevada has dry basins and mountains, little water, and no nearby ocean port. Technology changes possibilities, but cities still depend on water supplies.

The Dust Bowl showed why soil needs care

In the 1930s, drought struck the southern Great Plains. Farmers had removed grasses whose roots held the soil. Wind lifted the bare, dry topsoil into huge dust storms. Many families left.

Farmers learned ways to protect the ground. Rows of trees formed windbreaks. Plowing along the land's curves slowed runoff. Keeping crops or other plants on the ground helped hold soil in place.