Karen Hill

A sand sea, also called an erg, is a huge area of sand dunes. The largest sand sea in the Western Hemisphere is in central Nebraska. The Nebraska Sand Hills are a 20,000 square mile (52,000 sq km) dune field that covers the western third of the state. Because the area receives adequate rainfall, grasses … Read more

The word “badlands,” to geologists, means a region that has been badly eroded by water and wind. The result is an area of deep gullies and small, steep hills. The soil is poor or nonexistent, and few plants grow there. Badlands National Park in southwestern South Dakota is such a place. It features acres of … Read more

A plateau is an elevated area that spreads over a large region. A mesa, from the Spanish word for table, is a plateau that drops steeply off on all sides. A butte is a smaller mesa and is formed when a mesa erodes. If you visit the Four Corners area of the United States, the … Read more

The Earth is not a solid shell, but rather slabs of rock that scientists call Tectonic Plates. These plates, seven large plates and several smaller ones, have been moving for millions of years. They hold the ocean floors and the continents. Their movements cause new seafloor to form and earthquakes and volcanoes to occur. Mountain … Read more

California has so many earthquakes because the San Andreas Fault runs some 800 miles (1,288 km) through the state. The San Andreas Fault is a crack in the Earth’s crust that extends 10 miles (161 km) deep in some places. Geologists call it a strike-slip type of fault, meaning the rock on one side of … Read more

Earthquakes can not be predicted. Geologists can, however, calculate the probability of future earthquakes based on past activity. They know that very large earthquakes have happened along the southern part of the San Andreas Fault about every 150 years for the past 1,500 years or so. A large quake hit that area in 1857, so … Read more

On the Richter scale, Alaska’s Good Friday earthquake in 1964 in Prince William Sound measured 9.2, the strongest ever recorded. This quake was felt over a 500,000 square mile (1.3 million sq km) area, killed 114 people, and released more than 125 times the energy of the San Francisco earthquake of April 18, 1906. But … Read more

The Richter scale measures the magnitude, or size, of an earthquake by using a seismograph to measure the ground motion an earthquake produces. The scale is logarithmic. A measurement of 7 means an earthquake that has 10 times the ground motion of an earthquake that measures 6. We can’t feel an earthquake that has a … Read more

Even though most U.S. earthquakes happen in California and Alaska, earthquakes have been recorded in every U.S. state. The fewest earthquakes occur in Florida and North Dakota. The largest earthquake in the conterminous United States (i.e., excluding Alaska and Hawaii) happened on February 7, 1812, along the New Madrid Fault at New Madrid in southeastern … Read more

The United States does have active volcanoes. In fact, the United States is third in the world in the number of active volcanoes ever recorded, behind Indonesia and Japan. About 1,500 volcanoes have erupted all over the world in the past 10,000 years, and about 150 of those were in the United States. Today, active … Read more

Tsunami are huge, destructive waves that follow an earthquake or disturbance that has happened in the Earth’s crust under the ocean. The word is Japanese, meaning harbor wave; it’s pronounced “tsoo-nah-mee.” They’re wrongly called tidal waves, since they have nothing to do with the tides. During an earthquake, cracks open up along the ocean floor. … Read more

The 2000 Census showed that about 281 million people lived in the United States, excluding Puerto Rico and the U.S. island territories. It is estimated that the population of the United States in 2010 is about 310 million. The U.S. Census Bureau’s Web page features a population clock that shows the estimated U.S. population as … Read more

The distance between Cape Dezhnyov, Russia, and Cape Prince of Wales, Alaska, at the narrowest part of the Bering Strait, is 51 miles (82 km). The Bering Strait connects the Bering Sea, which is part of the Pacific Ocean, with the Arctic Ocean, and separates Asia and North America. The Bering Strait is named after … Read more

Alaska is the best place to see the aurora borealis in the United States but people in northern New England may be able to see auroras a few nights a year. Occasionally people in the northern Midwest and the Mid-Atlantic states can see them as well. They are best viewed on clear nights around midnight … Read more

Auroras, or aurora borealis (northern lights) in the Northern Hemisphere and aurora australis (southern lights) in the Southern Hemisphere, occur when the particles that constantly stream from the sun’s surface, called the solar wind, approach the Earth’s magnetic field. Some of these particles collide with oxygen and nitrogen atoms in the upper atmosphere, creating a … Read more

The Grand Canyon is not the deepest canyon in the United States. Hells Canyon, formed by the erosive action of the Snake River through the mountains on the Oregon–Idaho border, is more than 8,032 feet (2,448 m) deep at its lowest point and extends for 40 miles (64 km). The Grand Canyon, a gorge in … Read more

Louisiana, Missouri, Arkansas, Iowa, North Dakota, South Dakota, Nebraska, and Oklahoma were wholly contained in the Louisiana Purchase. In addition, most of the land in Kansas, Colorado, Wyoming, Montana, and Minnesota was part of the Louisiana Purchase. The French territory of Louisiana stretched northwest from the present state of Louisiana all the way to the … Read more

The regular rectangular farms that define much of the American Midwest and West are a result of a surveying technique called the township method that the federal government required surveyors to use in the Ohio Territory beginning in 1785. The township method continued to be used when the Louisiana Purchase was surveyed in the early … Read more

The 275 square mile (715 sq km) White Sands National Monument, in the northern part of New Mexico’s Chihuahuan Desert, is covered with sand made of gypsum crystals, which are usually white. Sand is defined as sediment created by the mechanical and chemical breakdown of rocks. In the United States, most desert and beach sand … Read more

The United States contains four desert regions: the Great Basin Desert, the Sonoran Desert, the Mojave Desert, and the Chihuahuan Desert. The Great Basin desert covers much of Nevada and spills into parts of Oregon, California, Idaho, and Utah. It is cooler than the other three desert regions and gets some snow in winter. The … Read more

The Continental Divide is the top, or crest, of the Rocky Mountains. All streams west of the divide eventually flow into the Pacific Ocean, while all streams east of the divide flow into the Atlantic Ocean or the Gulf of Mexico. The Continental Divide stretches from New Mexico all the way up to Alaska. The … Read more

Not every state in the United States has caves. Several states do not have caves, including North Dakota, Nebraska, Louisiana, Rhode Island, and Delaware. Most caves in the United States are karst caves. These caves formed when rainwater, which combines with the carbon dioxide in the air and forms a weak acid, seeped into rock … Read more

There are actually two falls on the Niagara River, the American Falls in New York State and the Horseshoe Falls in Canada. The Niagara River forms part of the U.S.–Canada border. The shape and location of Niagara Falls have changed many times over the centuries. Just 700 years ago, for example, there was just one … Read more

Florida has the lowest highest point in the United States, with its highest point is a place in Walton County that is 345 feet (105 m) above sea level. Walton County was created in 1824, and was named after George Walton, Secretary of the Florida territory from 1821 to 1826. It is estimated that in … Read more

Crater Lake in Oregon is the deepest lake in the United States, at 1,932 feet (588 m). The lake was formed entirely by rain and snow falling into the collapsed volcanic crater of Mount Mazama, in the Cascade Mountains. Mount Mazama’s top fell in about 7,700 years ago. The lake is almost 6 miles (10 … Read more

Lake Superior is the largest freshwater lake in the United States, and in the world as well. It covers an area of 31,800 square miles (82,680 sq km). Lake Superior holds about 2,900 cubic miles, or 12,000 cubic kilometers. It is the northernmost of the Great Lakes and touches Wisconsin, Minnesota, and Michigan as well … Read more

Although surrounded by the Pacific Ocean, the islands that make up the state of Hawaii have a total of only 36 square miles (94 sq km) of inland water. Alaska has the most water, with 17,501 square miles (45,502 sq km). Hawaii is the only state of the United States that is completely surrounded by … Read more

Michigan borders four of the five Great Lakes: Superior, Michigan, Huron, and Erie. The state of Michigan does not touch Lake Ontario, which is bordered by New York and the province of Ontario, Canada. To remember the names of the Great Lakes, think of HOMES, for Huron, Ontario, Michigan, Erie, and Superior. The Great Lakes … Read more

All but one of the Great Lakes border on Canada. Lake Michigan lies entirely within the United States. The Great Lakes hold about one fifth of the world’s freshwater, covering an area of about 95,000 square miles (247,000 sq km) altogether. If you could empty all the water out of the Great Lakes and spread … Read more

The Mississippi River is 2,340 miles (3,767 km) long, making it the longest in the United States. The Missouri River, at 2,315 miles (3,727 km) long, is the second longest, and together they form the fourth longest river system in the world. The Missouri River begins its journey in the Rocky Mountains of southwestern Montana, … Read more

The highest waterfall in the United States is in Yosemite National Park in California. Yosemite Falls is made up of an upper fall, the middle cascades, and a lower fall totaling 2,425 feet (739 m). It is the fifth tallest waterfall in the world, as tall as Chicago’s Sears Tower and Paris’s Eiffel Tower combined. … Read more

Sinkholes are common in humid areas where limestone forms the underlying bedrock. Geologists refer to these areas as karst. Sinkholes are formed when ground water reacts chemically with the limestone and dissolves it over time, causing either a depression or a hole in the ground. Large holes result when the dissolved limestone is part of … Read more

The Gulf of Mexico part of the Atlantic Ocean. By definition, a gulf is a part of a sea or ocean that extends into land. The Caribbean Sea is also part of the Atlantic Ocean. Three times more water from U.S. rivers drains into the Atlantic Ocean than into the Pacific. The Gulf of Mexico … Read more

In Florida, where almost 10 people each year, on average, are killed by lightning strikes from thunderstorms. Most of the victims are men, and most are on golf courses. Nearly five people on average are killed each year by lightning in North Carolina and Texas, two other states where golfers and thunderstorms frequently mix. There … Read more

The Ten Deadliest Tornadoes in the United States were: Missouri, Illinois, Indiana, March 18, 1925, 695 deaths. Natchez, Mississippi, May 6, 1840, 317 deaths. St. Louis, Missouri, May 27, 1896, 255 deaths. Tupelo, Mississippi, April 5, 1936, 216 deaths. Gainesville, Georgia, April 6, 1936, 203 deaths. Woodward, Oklahoma, April 9, 1947, 181 deaths. Amite, Louisiana, … Read more

There are five major mountain ranges in the United States: the Appalachian Mountains in the East; the Rocky Mountains in the Southwest and West, from Colorado to the Canadian border and beyond; the Cascade Mountains in the Pacific Northwest; the Sierra Nevada in the far West; and the Alaska Range, a segment of the Coast … Read more

For the 48 conterminous states, the geographic center is near Lebanon, Kansas. If you take Alaska into account, the geographic center of the United States becomes a point near Castle Rock, South Dakota. In 1918 a monument was erected at the site to mark the spot. In 2000, the population of Lebanon, Kansas was 303. … Read more

The Appalachian Mountains are not as tall and jagged as the Rocky Mountains because they are so much older and have been worn down by weathering and erosion over millions of years. The Appalachians run for about 2,000 miles (3,218 km) from Newfoundland, Canada, through Maine all the way south to central Alabama. They are … Read more

Mount McKinley, also called Denali, in Alaska is the tallest mountain in the United States, at 20,320 feet (6,193 m). On a clear day the peak can be seen from as far as 250 miles (402 km) away. The next 16 highest peaks in the United States also are in Alaska. Number 18 is Mount … Read more

The Appalachian Trail, often called the A.T., is a footpath that runs for 2,167 miles (3,488 km) along the crests and through the valleys of the Appalachian Mountains. The trail’s northern end is Katandin, Maine. From there it passes through New Hampshire, Vermont, Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, Maryland, West Virginia, Virginia, Tennessee, … Read more

Denali is the ancient Indian name for Mount McKinley, meaning “The Great One” or “The High One.” It is in Denali National Park and Preserve, about 130 miles (209 km) north of Anchorage, Alaska. The mountain was renamed for President McKinley in 1896. Mount McKinley is a granitic pluton which has been uplifted by tectonic … Read more

At 282 feet (85 m) below sea level, the lowest point in the United States is Bad Water, in Death Valley, California. At Badwater, significant rainstorms flood the valley bottom periodically, covering the salt pan with a thin sheet of standing water. The sign marking “sea level” on the cliff above Badwater is a popular … Read more

An avalanche is defined as an extremely rapid slide and fall of snow, rocks, and trees. Between 1985 and 1998 a total of 240 people died in avalanches in the United States. The most accidents occurred in Colorado, followed by Alaska, Utah, and Montana. Only a few people died within ski area boundaries, most who … Read more

Phoenix, Arizona, on average, experiences sunny or partly cloudy skies 81 percent of the days in a year. As a result, Phoenix, Arizona is known as the sunniest city in the United States. Phoenix, Arizona is the fifth most populated city in the United States, making it the most populous state capital. Following Phoenix as … Read more

Chicago may be called the Windy City, but the nation’s windiest city is Cheyenne, Wyoming, where the average annual wind speed clocks in at 12.9 miles (21 km) per hour. Chicago, at 10.4 miles (17 kin) per hour, is calm compared to Cheyenne and these other cities, where average winds speeds range from 12.6 miles … Read more

Tornadoes usually form in the spring when thunderstorms create strong vertical wind shears that cause updrafts of wind to rotate at high speeds. This violently rotating column of wind extends from the base of the thunderstorm cloud to the ground. On the ground, the tornado’s swirling winds gather up dust and debris, which is why … Read more

Since 1980, there have been more than 44 weather related disasters in which damages and costs have exceeded $1 billion. The worst year was 1998, when seven such disasters took place. Here are the top 10: Drought and heat wave, central and eastern states, 1980: $44 billion, 10,000 deaths Drought and heat wave, central and … Read more

Los Angeles, California, has the highest relative humidity in the United States, where the average July afternoon humidity reaches 68 percent. Not much better are runner ups San Juan, Puerto Rico (67 percent); San Diego, California (66 percent); Juneau, Alaska (66 percent); New Orleans, Louisiana (66 percent); Miami, Florida (63 percent); Mobile, Alabama (62 percent); … Read more

Tornado Alley generally extends from South Dakota through Kansas and Oklahoma into northern Texas. This area is known for its high average number of tornadoes per year, about 20. But tornadoes can occur in all 50 states. Oklahoma City is hit by more tornadoes than any city in the nation, a total of 103 struck … Read more

It is difficult to directly measure ground speeds of tornadoes. But scientists managed to determine that a tornado that passed near Bridge Creek, Oklahoma, on May 3, 1999, was traveling at 318 miles (512 km) per hour, the highest winds ever recorded on the Earth’s surface. Bridge Creek was one of several communities hardest hit … Read more

A tornado that rampaged for 219 miles (353 km) through Missouri, Illinois, and Indiana in March 1925 is believed to have killed nearly 700 people. In one town alone, Murphysboro, Illinois, at least 234 people died. That record still stands for the most fatalities in a single U.S. town or city due to a tornado. … Read more

Most tornadoes, but not all, in the Northern Hemisphere rotate counterclockwise, or cyclonically. Most tornadoes in the Southern Hemisphere, in Australia for example, rotate clockwise, or anticyclonically. Every once in a while, an anticyclonic tornado is seen in the United States, one struck near Sunnyvale, California, in 1998. But usually they take the form of … Read more

Yes, it can snow in the desert, in fact, snow has fallen in almost every part of the United States at one time or another. The most snow ever reported in Phoenix, Arizona, was 1 inch (2.5 cm), an event that has happened there twice, the first time on January 20, 1933, and the second … Read more

The National Weather Service says that an average of 105 snow producing storms affect the United States each year. Most last from 2 to 5 days and bring snow to parts of several states. The snowiest city in the United States is Sault Ste. Marie, Michigan. It gets an average of 117 inches (297 cm) … Read more

Seattle has a reputation for rainy weather, but it’s not the rainiest place in the United States. For example, New Orleans, Louisiana, and Mobile, Alabama, each average more than 61 inches (155 cm) of rain a year, followed by Miami, Florida (56 in/142 cm) and Juneau, Alaska (54 in/137 cm). Seattle receives an average of … Read more

In the past 50 years or so, Pennsylvania tops the list of states experiencing extensive damage from flooding, followed by California, Louisiana, Iowa, Texas, and Missouri, in that order. Floods result from a volume of water, such as a river or lake, which overflows or breaks levees. The word “flood” comes from the Old English … Read more

The record for the most abrupt temperature change in the United States is held by Spearfish, South Dakota, where it took just 2 minutes to warm up from -4° to 45° Fahrenheit on August 29, 1936. The U.S. location holding the record for the greatest range of temperatures over a 24-hour period is Browning, Montana, … Read more

When a tropical cyclone reaches a wind speed of 39 miles (63 km) per hour, the World Meteorological Association assigns it a name from one of six lists of names it rotates yearly. If a hurricane is especially deadly or causes extensive damage, its name is “retired” and a new name starting with the same … Read more

The fastest wind speed on record, not counting tornadoes, in the United States and the world took place on Mount Washington, in New Hampshire, on April 12, 1934. That day, the wind speed was recorded at 231 miles (372 km) per hour. This record is also the world record for wind gusts. Mount Washington also … Read more

The coldest day in the United States happened on January 23, 1971, in Prospect Creek, Alaska, when the temperature dipped to -79.8° Fahrenheit. Every U.S. state except one has experienced a day in which the temperature fell below 0° Fahrenheit. The exception is Hawaii, where the lowest temperature on record is 12° Fahrenheit, on May … Read more

The hottest day on record in the United States happened on July 10, 1918, in Greenland Ranch, California (in Death Valley), when the thermometer reached 134° Fahrenheit. Death Valley is an arid desert basin that covers parts of eastern California and western Nevada. At one time or another, every U.S. state has recorded a high … Read more

Officially, the Atlantic hurricane season runs from June 1 to November 30. But most hurricanes develop between August and October, with the largest number occurring from early to mid-September. In September 1900, the worst natural disaster ever in the United States, the Galveston hurricane, destroyed most of the city of Galveston, Texas. At least 8,000 … Read more

Both a hurricane and a typhoon are names for strong tropical cyclones. The regional name for a tropical cyclone that forms in the northwestern Pacific Ocean west of the dateline is typhoon. Hurricane is the regional name for a tropical cyclone that forms in the Atlantic Ocean, the Gulf of Mexico, the Caribbean Sea, the … Read more

Hurricanes form in both the Atlantic and the Pacific Ocean basins, in tropical or subtropical regions. Because hurricanes tend to move toward the west or the northwest, they usually move toward the U.S. East Coast but move away from the U.S. West Coast. Another reason why hurricanes never strike the U.S. West coast is that … Read more

Is it usually warmer in New York City than in rural New Jersey because cities tend to be warmer than the surrounding countryside. This is known as the urban heat island phenomenon. Cities are warmer in summer and winter because they are full of concrete and asphalt, which retain heat better than soil and fields. … Read more

Also called a nor’easter, a northeaster type of winter storm blows into North America from the northeast and brings strong winds and precipitation to New England and the Mid-Atlantic states. They occur most often between September and April. A Northeaster is usually described as a low pressure area whose center of rotation is just off … Read more

Santa Anas are similar to chinooks. These winds blow from Utah and Nevada over the Sierra Nevada mountains and into southern California. The air they bring is very dry, which causes vegetation to dehydrate, putting the region at risk for wildfires. Winds in Hawaii have their own special names: Kona is a southwesterly wind that … Read more

A Chinook is a term used to describe a type of wind that occurs in the Rocky Mountains. Winds generally blow from west to east across the United States. Chinooks often result when air from the west blows over and down the eastern sides of the Rocky Mountains. These winds can gust up to 100 … Read more

Average annual temperatures in the United States have increased by almost 1° Fahrenheit since the late 1800s. Half of that increase occurred in just the past 40 years. In fact, the four warmest years since 1860 all occurred during the 1990s. But it’s not getting warmer everywhere; in fact, parts of the southeastern United States … Read more

Latitude is only one factor of several that determine climate in any particular region. San Francisco’s position between 30° and 40° latitude and its location on the western side of the North American continent place it in the climate subcategory called Mediterranean. People living there experience warm, dry summers and mild, wet winters. Washington, D.C.’s, … Read more

The term weather usually refers to what is happening in the atmosphere at a specific location on a day to day basis. Climate refers to weather conditions that tend to occur in an area over a long period of time. Climates in the United States vary widely. In fact, they include five of the six … Read more

El Nino refers to a cycle that occurs every few years in which warm water accumulates in the eastern part of the Pacific Ocean around the equator. Some scientists think this cycle may be caused by changes in trade wind patterns. During an El Nino year, places such as Australia, North America, South America, and … Read more

During an El Nino year in the continental United States, winter temperatures are generally warmer than normal in the North and cooler than normal in the South. During the winter of a La Nina year, the southeastern states generally have warmer winter weather than normal, while the northwestern states are cooler than normal. El Nino … Read more

Global warming refers to the theory that the Earth’s atmosphere, specifically, the troposphere or lower atmosphere, is retaining more heat because of an increase in the amount of greenhouse gases. These gases include carbon dioxide, methane, and nitrous oxide, and together they prevent about 30 percent of the heat that leaves the Earth’s surface from … Read more

In 2000, a total of 164 million computers were in use in the United States, the largest number in the world. Japan, Germany, Great Britain, France, and Italy, in that order, were the next-largest computer users. The world total was 579 million computers. It is estimated that in 2010, more than 80%, or 250 million … Read more

High speed trains, often called bullet trains, are being planned in several regions of the United States. A high speed train is defined as one that can run between 150 and 320 miles per hour (242 and 515 km/hr). Amtrak’s Acela trains travel at speeds up to 150 miles per hour and are now connecting … Read more

The United States exports a large portion of its farm products to other countries. For example, U.S. farmers are the world’s leading exporters of corn, in 1999 they sold more than one fifth of the corn they grew to other countries. The United States is the world’s second largest exporter of wheat, the countries of … Read more

More than 6 of every 10 Internet users in the world live in the United States. But if you consider the percentage of a country’s population that uses the Internet, the United States ranks fourth, behind Canada, Sweden, and Finland. In 2000, about 280 million people worldwide were using the Internet. In 2010, there were … Read more

Believe it or not, most people in the world do not have telephones in their homes. For example, according to the World Bank, only one of every five people in Russia has a phone line. If you lived there, you’d have to wait an average of five years to get phone service. The wait is … Read more

The United States consumes more electricity than any other country in the world. The United States generates and consumes about one fourth of all the electricity worldwide. China is second, consuming about one tenth of the world’s electricity, followed by Russia, Japan, Germany, India, and Canada, in that order. The average person in the United … Read more

The United States does not have more working women than any other country. The United States is in sixth place, with about 71 percent of women working for pay. Iceland, Sweden, Norway, Denmark, and Finland all have a higher percentage of women who work for pay. Of the world’s 6 billion people, nearly 1 billion … Read more

The United States is the world’s leading air polluter, responsible for one fourth of all carbon dioxide emissions. Carbon dioxide emissions result from burning fossil fuels, such as gasoline, oil, natural gas, and coal. China is the world’s second worst air polluter, accounting for 12 percent of carbon dioxide emissions, followed by Russia, Japan, Indonesia, … Read more

About one fifth of electricity generated in the United States comes from nuclear power plants. But most of the electricity we use, about one half, is made by burning coal. It’s no coincidence that the United States is the world’s leading coal producer. Natural gas and petroleum generate another one fifth of U.S. electricity, and … Read more

The United States has nearly 4 million miles (6.4 million km) of roads, most of which are paved. That is more than five and a half times China’s 719,000 miles (1.16 million km) of roads. China has about the same amount of land area as the United States. If every family car and truck in … Read more

The United States is the richest country in the world by GNP, and has held the position for a while now. Economists measure a country’s wealth by looking at the value of the goods and services it produces each year. They call this the GNP, which stands for gross national product. The United States had … Read more

Americans born today can expect, on average, to live about 77 years. A person born in sub-Saharan Africa today can expect to live only 49 years. People born in Japan can expect to live the longest, to age 80, while people in Iceland, Sweden, and Switzerland will live to age 79, on average. As a … Read more

The population density of the United States is 77 people per square mile. The most densely populated country in the world is Monaco, with more than 55,000 people per square mile. Of course, Monaco is one of the world’s smallest countries, at just a little over 0.5 square mile (1.3 sq km). The country where … Read more

The U.S. Census Bureau predicts that 338 million people will be living in the United States by 2025, about 57 million more people than in 2000. One reason for this growth is that each year nearly 1 million immigrants come to the United States to live. If it weren’t for these immigrants, the U.S. population … Read more

The width of the United States depends on whether Alaska or Hawaii is included. Measured from the farthest points west and east in the conterminous United States, meaning the 48 states that have a common boundary, which are West Quoddy Head, Maine, and Point Arena, California, the United States is 2,892 miles (4,656 km) wide. … Read more