The Continental Divide The Continental Divide is a ridge of high ground that runs irregularly north and south through the Rocky Mountains and separates eastward-flowing from westward-flowing streams. The waters that flow eastward empty into the Atlantic Ocean, chiefly by way of the Gulf of Mexico; those that flow westward empty into the Pacific. Every continent with the exception of Antarctica has a continental divide.

Mason and Dixon's Line Mason and Dixon's Line (often called the Mason-Dixon Line) is the boundary between Pennsylvania and Maryland, running at a north latitude of 39°43'19.11". The greater part of it was surveyed from 1763–1767 by Charles Mason and Jeremiah Dixon, English astronomers who had been appointed to settle a dispute between the colonies. As the line was partly the boundary between the free and the slave states, it has come to signify the division between the North and the South.

World Heritage Sites in the United States The United Nations Educational, Scientific, and Cultural Organization (UNESCO) has identified 878 World Heritage sites that it considers of “outstanding universal value.” In the United States, there are 20 of these sites; the 17 that are natural sites are listed below. The World Heritage Web site is as follows: http://whc.unesco.org /en/list/. Cahokia Mounds State Historic Site, Illinois:BetweenA.D.900 andA.D.1500 the Cahokia site was the regional center for the Mississippian Indian culture. Named for the Cahokia Indians who came after them, Cahokia features the largest prehistoric earthen constructions in the Americas, a testament to the sophisticated engineering skills of Mississippian culture. Carlsbad Caverns National Park, New Mexico:Carlsbad Caverns National Park is a network of more than 80 limestone caves, including the nation's deepest—1,597 feet—and third longest. The Lechuguilla Cave is particularly noteworthy for its beautiful stalagtites and stalagmites. Chaco Culture National Historical Park, New Mexico:BetweenA.D.900 andA.D.1100, the Anasazi built large multistory stone villages and an impressive 400-mile road system in Chaco canyon exemplifying their engineering and construction talents. Everglades National Park, Florida:The Everglades, or “River of Grass” as the Seminoles called it, is formed by a river of fresh water 6 inches deep and 50 miles wide that flows slowly across the expanse of land of sawgrass marshes, pine forests, and mangrove islands. More than 300 species of birds live in the park as well as alligators, manatees, and Florida panthers. Glacier Bay National Park and Preserve, Alaska:The park is made up of a huge chain of great tidewater glaciers and a dramatic range of landscapes, from rocky terrain recently covered by ice to lush temperate rain forest. Brown and black bears, mountain goats, whales (including humpbacks), seals, and eagles can be found within the park. Grand Canyon National Park, Arizona:The Grand Canyon is among Earth's greatest ongoing geological spectacles. About 65 million years ago in Earth's shifting, a huge area of land was lifted a mile and a half above sea level, forming what is now the Colorado Plateau. For the last 6 to 10 million years, the Colorado River has been slowly carving its way down through the center, exposing the many colorful strata of rock. Great Smoky Mountains National Park, North Carolina/Tennessee:“Place of Blue Smoke” was the name given by the Cherokee Indians to these Appalachian Highlands. The forest here exudes water vapor and oily residues which create a smoke-like haze that surrounds the peaks and fills the valleys. The park is one of the world's finest temperate deciduous forests. Hawaii Volcanoes National Park, Hawaii:It is thought that the Hawaiian islands were created when molten rock pushed through Earth's crust, forming volcanoes. The two most spectacular live volcanoes are Kilauea and Mauna Loa. Mammoth Cave National Park, Kentucky:Mammoth Cave, as its name suggests, is the world's most extensive cave system, with 345 miles of passages. Water seeping into the cave creates stalactites, stalagmites, and white gypsum crystal formations. Rare and unusual animals, such as blind fish and colorless spiders, demonstrate adaptation to the absolute blackness and isolation. Mesa Verde National Park, Colorado:In the sixth century, the Anasazi, or “Ancient Ones,” established villages on the high, flat land in southwestern Colorado. In the late 1100s they began constructing multistory stone apartment houses, or pueblos, tucked on ledges and under rock overhangs. Olympic National Park, Washington:The park encompasses not only snow-capped Mount Olympus, glaciers, alpine meadows, and rocky Pacific Mountain coastline, but also one of the few temperate rain forests in the world. The luxuriant forest is created by the warm, moisture-laden air from the Pacific meeting the mountains, resulting in a dense, green, jungle-like world. Papahanaumokuakea:This string of isolated islands is the largest conservation area in the United States and one of the largest marine conservation areas in the world. It covers 139,797 square miles of the Pacific Ocean. The extensive coral reefs found in Papahanaumokuakea are home to more than 7,000 marine species, one-quarter of which are found only in the Hawaiian Archipelago. Many of the islands and shallow water environments are important habitats for rare species, such as the threatened green sea turtle and the endangered Hawaiian monk seal. Papahanaumokuakea is also of great cultural importance to Native Hawaiians with significant cultural sites found on the islands of Nihoa and Mokumanamana.Source: http://papahanaumok uakea.gov.

Geysers in the United States Geysers are natural hot springs that intermittently eject a column of water and steam into the air. They exist in many parts of the volcanic regions of the world such as Japan and South America but their greatest development is in Iceland, New Zealand, and Yellowstone National Park. There are 120 named geysers in Yellowstone National Park, Wyoming, and perhaps half that number unnamed. Most of the geysers and the 4,000 or more hot springs are located in the western portion of the park. The most important are the following: Norris Geyser Basin has 24 or more active geysers; the number varies. There are scores of steam vents and hot springs.Steamboatis the largest active geyser in the world, sending water more than 300 ft. into the air for 3 to 20 minutes. It emits water every few minutes, but its major eruptions are infrequent and erratic.Valentineerupts 50–75 ft. at intervals varying from 18 hr. to 3 days or more.Minutéerupts 15–20 ft. high, several hours apart. Others include:Fearless, Veteran, Vixen, Corporal, Whirligig, Little Whirligig,andPinwheel. Lower Geyser Basin has at least 18 active geysers.Fountainthrows water 50–75 ft. in all directions at unpredictable intervals.Clepsydraerupts violently from 4 vents up to 30 ft.Great Fountainplays every 8 to 15 hr. in spurts from 30 to 90 ft. high. Midway Geyser Basin has vast steaming terraces of red, orange, pink and other colors; there are pools and springs, including the beautifulGrand Prismatic Spring. Excelsiorcrater discharges boiling water into Firehole River at the rate of 6 cu. ft. per second. Gianterupts up to 200 ft. at intervals of 21/2 days to 3 mo; eruptions last about 11/2 hr.Daisysends water up to 75 ft. but is irregular and frequently inactive. Old Faithful,the most famous geyser in the park, sends up a column varying from 116 to 175 ft. at intervals of about 65 min, varying from 33 to 90 min. Eruptions last about 4 min, during which time about 12,000 gal. are discharged. Giantessseldom erupts, but during its active period sends up streams 150–200 ft. Lionplays up to 60 ft. every 2–4 days when active;Little Cubup to 10 ft. every 1–2 hr.Big CubandLionessseldom erupt. There are no geysers in the Mammoth Hot Springs area. The formation is travertine. Sides of a hill are steps and terraces over which flow the steaming waters of hot springs laden with minerals. Each step is tinted by algae to many shades of orange, pink, yellow, brown, green, and blue. Terraces are white where no water flows.

Rivers of the United States (350 or more miles long) Alabama-Coosa(600 mi.; 966 km): From junction of Oostanula and Etowah R. in Georgia to Mobile R. Altamaha-Ocmulgee(392 mi.; 631 km): From junction of Yellow R. and South R., Newton Co. in Georgia to Atlantic Ocean. Apalachicola- Chattahoochee(524 mi.; 843 km): From Towns Co. in Georgia to Gulf of Mexico in Florida. Arkansas(1,459 mi.; 2,348 km): From Lake Co. in Colorado to Mississippi R. in Arkansas. Brazos(923 mi.; 1,490 km): From junction of Salt Fork and Double Mountain Fork in Texas to Gulf of Mexico. Canadian(906 mi.; 1,458 km): From Las Animas Co. in Colorado to Arkansas R. in Oklahoma. Cimarron(600 mi.; 966 km): From Colfax Co. in New Mexico to Arkansas R. in Oklahoma. Colorado(1,450 mi.; 2,333 km): From Rocky Mountain National Park in Colorado to Gulf of California in Mexico. Colorado(862 mi.; 1,387 km): From Dawson Co. in Texas to Matagorda Bay. Columbia(1,243 mi.; 2,000 km): From Columbia Lake in British Columbia to Pacific Ocean (entering between Oregon and Washington). Colville(350 mi.; 563 km): From Brooks Range in Alaska to Beaufort Sea. Connecticut(407 mi.; 655 km): From Third Connecticut Lake in New Hampshire to Long Island Sound in Connecticut. Cumberland(720 mi.; 1,159 km): From junction of Poor and Clover Forks in Harlan Co. in Kentucky to Ohio R. Delaware(390 mi.; 628 km): From Schoharie Co. in New York to Liston Point, Delaware Bay. Gila(649 mi.; 1,044 km): From Catron Co. in New Mexico to Colorado R. in Arizona. Green(360 mi.; 579 km): From Lincoln Co. in Kentucky to Ohio R. in Kentucky. Green(730 mi.; 1,175 km): From Sublette Co. in Wyoming to Colorado R. in Utah. Illinois(420 mi.; 676 km): From St. Joseph Co. in Indiana to Mississippi R. at Grafton in Illinois. James(sometimes calledDakota) (710 mi.; 1,143 km): From Wells Co. in North Dakota to Missouri R. in South Dakota. Kanawha-New(352 mi.; 566 km): From junction of North and South Forks of New R. in North Carolina, through Virginia and West Virginia (New R. becoming Kanawha R.), to Ohio R. Kansas(743 mi.; 1,196 km): From source of Arikaree R. in Elbert Co., Colorado, to Missouri R. at Kansas City, Kansas. Koyukuk(470 mi.; 756 km): From Brooks Range in Alaska to Yukon R. Kuskokwim(724 mi.; 1,165 km): From Alaska Range in Alaska to Kuskokwim Bay. Licking(350 mi.; 563 km): From Magoffin Co. in Kentucky to Ohio R. at Cincinnati in Ohio. Little Missouri(560 mi.; 901 km): From Crook Co. in Wyoming to Missouri R. in North Dakota. Milk(625 mi.; 1,006 km): From junction of forks in Alberta Province to Missouri R. Mississippi(2,348 mi.; 3,779 km): From Lake Itasca in Minnesota to mouth of Southwest Pass in Louisiana. Mississippi-Missouri-Red Rock(3,710 mi.; 5,970 km): From source of Red Rock R. in Montana to mouth of Southwest Pass in Louisiana. Missouri(2,315 mi.; 3,726 km): From junction of Jefferson R., Gallatin R., and Madison R. in Montana to Mississippi R. near St. Louis. Missouri-Red Rock(2,540 mi.; 4,090 km): From source of Red Rock R. in Montana to Mississippi R. near St. Louis. Mobile-Alabama-Coosa(645 mi.; 1,040 km): From junction of Etowah R. and Oostanula R. in Georgia to Mobile Bay. Neosho(460 mi.; 740 km): From Morris Co. in Kansas to Arkansas R. in Oklahoma. Niobrara(431 mi.; 694 km): From Niobrara Co. in Wyoming to Missouri R. in Nebraska. Noatak(350 mi.; 563 km): From Brooks Range in Alaska to Kotzebue Sound. North Canadian(800 mi.; 1,290 km): From Union Co. in New Mexico to Canadian R. in Oklahoma. North Platte(618 mi.; 995 km): From Jackson Co. in Colorado to junction with South Platte R. in Nebraska to form Platte R. Ohio(981 mi.; 1,579 km): From junction of Allegheny R. and Monongahela R. at Pittsburgh to Mississippi R. between Illinois and Kentucky. Ohio-Allegheny(1,306 mi.; 2,102 km): From Potter Co. in Pennsylvania to Mississippi R. at Cairo in Illinois. Osage(500 mi.; 805 km): From east-central Kansas to Missouri R. near Jefferson City in Missouri. Ouachita(605 mi.; 974 km): From Polk Co. in Arkansas to Red R. in Louisiana. Pearl(411 mi.; 661 km): From Neshoba County in Mississippi to Gulf of Mexico (Mississippi-Louisiana). Pecos(926 mi.; 1,490 km): From Mora Co. in New Mexico to Rio Grande in Texas. Pee Dee-Yadkin(435 mi.; 700 km): From Watauga Co. in North Carolina to Winyah Bay in South Carolina. Pend Oreille–Clark Fork(531 mi.; 855 km): Near Butte in Montana to Columbia R. on Washington-Canada border. Platte(990 mi.; 1593 km): From source of Grizzly Creek in Jackson Co., Colorado, to Missouri R. south of Omaha, Nebraska. Porcupine(569 mi.; 916 km): From Yukon Territory, Canada, to Yukon R. in Alaska. Potomac(383 mi.; 616 km): From Garrett Co. in Maryland to Chesapeake Bay at Point Lookout in Maryland.