The term "United States," when used in the geographical sense, refers to the contiguous United States, the state of Alaska, the island state of Hawaii, the five insular territories of Puerto Rico, Northern Mariana Islands, U.S. Virgin Islands, Guam, and American Samoa, and minor outlying possessions. The United States shares land borders with Canada and Mexico and maritime borders with Russia, Cuba, The Bahamas, and many other countries, mainly in the Caribbeanin addition to Canada and Mexico. The northern border of the United States with Canada is the world's longest bi-national land border.
The San Luis Valley is a region in south-central Colorado with a small portion overlapping into New Mexico. The valley is approximately 122 miles (196 km) long and 74 miles (119 km) wide, extending from the Continental Divide on the northwest rim into New Mexico on the south. It contains 6 counties and portions of 3 others. It is an extensive high-elevation depositional basin of approximately 8,000 square miles (21,000 km2) with an average elevation of 7,664 feet (2,336 m) above sea level. The valley is a section of the Rio Grande Rift and is drained to the south by the Rio Grande, which rises in the San Juan Mountains to the west of the valley and flows south into New Mexico. The San Luis Valley has a cold desert climate but has substantial water resources from the Rio Grande and groundwater.
The Great Artesian Basin (GAB), located in Australia, is the largest and deepest artesian basin in the world, stretching over 1,700,000 square kilometres (660,000 sq mi), with measured water temperatures ranging from 30 to 100 °C. The basin provides the only source of fresh water through much of inland Australia.
The Continental Divide of the Americas is the principal, and largely mountainous, hydrological divide of the Americas. The Continental Divide extends from the Bering Strait to the Strait of Magellan, and separates the watersheds that drain into the Pacific Ocean from those river systems that drain into the Atlantic and Arctic Ocean, including those that drain into the Gulf of Mexico, the Caribbean Sea, and Hudson Bay.
The Arkansas River is a major tributary of the Mississippi River. It generally flows to the east and southeast as it traverses the U.S. states of Colorado, Kansas, Oklahoma, and Arkansas. The river's source basin lies in Colorado, specifically the Arkansas River Valley. The headwaters derive from the snowpack in the Sawatch and Mosquito mountain ranges. It flows east into Kansas and finally through Oklahoma and Arkansas, where it meets the Mississippi River.
The San Joaquin River is the longest river of Central California. The 366-mile (589 km) long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suisun Bay, San Francisco Bay, and the Pacific Ocean. An important source of irrigation water as well as a wildlife corridor, the San Joaquin is among the most heavily dammed and diverted of California's rivers.
The San Joaquin Valley is the southern half of California's Central Valley, an area drained by the San Joaquin River. Famed as a major breadbasket, the San Joaquin Valley is an important source of food, producing a significant part of California's agricultural output.
The San Gabriel River is a mostly urban waterway flowing 58 miles (93 km) southward through Los Angeles and Orange Counties, California in the United States. It is the central of three major rivers draining the Greater Los Angeles Area, the others being the Los Angeles River and Santa Ana River. The river's watershed stretches from the rugged San Gabriel Mountains to the heavily developed San Gabriel Valley and a significant part of the Los Angeles coastal plain, emptying into the Pacific Ocean between the cities of Long Beach and Seal Beach.
The Valley of Mexico, sometimes also called Basin of Mexico, is a highlands plateau in central Mexico. Surrounded by mountains and volcanoes, the Valley of Mexico was a centre for several pre-Columbian civilizations including Teotihuacan, the Toltec, and the Aztec Empire. The valley used to contain five interconnected lakes called Lake Zumpango, Lake Xaltocan, Lake Xochimilco, Lake Chalco and the largest, Lake Texcoco, covering about 1,500 square kilometers (580 sq mi) of the valley floor. When the Spaniards arrived in the Valley of Mexico, it had one of the highest population concentrations in the world with about one million people. After the conquest of the Aztec Empire, the Spaniards rebuilt the largest and most dominant city, Mēxihco Tenōchtitlan, renaming it Ciudad de México and over time began to drain the lakes' waters to control flooding.
The Oxnard Plain is a large coastal plain in southwest Ventura County, California, United States surrounded by the mountains of the Transverse ranges. The cities of Oxnard, Camarillo, Port Hueneme and much of Ventura as well as the unincorporated communities of Hollywood Beach, El Rio, Saticoy, Silver Strand Beach, and Somis lie within the over 200-square-mile alluvial plain (520 km2). The population within the plain comprises a majority of the western half of the Oxnard-Thousand Oaks-Ventura Metro Area and includes the largest city along the Central Coast of California. The 16.5-mile-long coastline (26.6 km) is among the longest stretches of continuous, linear beaches in the state.
The geography of Texas is diverse and large. Occupying about 7% of the total water and land area of the U.S., it is the second largest state after Alaska, and is the southernmost part of the Great Plains, which end in the south against the folded Sierra Madre Oriental of Mexico. Texas is in the South Central United States of America, and is considered to form part of the U.S. South and also part of the U.S. Southwest.
The geography of Mesoamerica describes the geographic features of Mesoamerica, a culture area in the Americas inhabited by complex indigenous pre-Columbian cultures exhibiting a suite of shared and common cultural characteristics. Several well-known Mesoamerican cultures include the Olmec, Teotihuacan, the Maya, the Aztec and the Purépecha. Mesoamerica is often subdivided in a number of ways. One common method, albeit a broad and general classification, is to distinguish between the highlands and lowlands. Another way is to subdivide the region into sub-areas that generally correlate to either culture areas or specific physiographic regions.
North America is the third largest continent, and is also a portion of the third largest supercontinent if North and South America are combined into the Americas and Africa, Europe, and Asia are considered to be part of one supercontinent called Afro-Eurasia. With an estimated population of 580 million and an area of 24,709,000 km2 (9,540,000 mi2), the northernmost of the two continents of the Western Hemisphere is bounded by the Pacific Ocean on the west; the Atlantic Ocean on the east; the Caribbean Sea on the south; and the Arctic Ocean on the north.
The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western Interior Seaway. The usage of the name Dakota for this particular Albian-Cenomanian strata is exceptionally widespread; from British Columbia and Alberta to Montana and Wisconsin to Colorado and Kansas to Utah and Arizona. It is famous for producing massive colorful rock formations in the Rocky Mountains and the Great Plains of the United States, and for preserving both dinosaur footprints and early deciduous tree leaves.
The Upper Rhine Plain, Rhine Rift Valley or Upper Rhine Graben is a major rift, about 350-kilometre-long (220 mi) and on average 50-kilometre-wide (31 mi), between Basel in the south and the cities of Frankfurt/Wiesbaden in the north. Its southern section straddles the France–Germany border. It forms part of the European Cenozoic Rift System, which extends across Central Europe. The Upper Rhine Graben formed during the Oligocene, as a response to the evolution of the Alps to the south. It remains active to the present day. Today, the Rhine Rift Valley forms a downfaulted trough through which the river Rhine flows.
In the history of the American frontier, pioneers built overland trails throughout the 19th century, especially between 1829 and 1870, as an alternative to sea and railroad transport. These immigrants began to settle much of North America west of the Great Plains as part of the mass overland migrations of the mid-19th century. Settlers emigrating from the eastern United States did so with various motives, among them religious persecution and economic incentives, to move from their homes to destinations further west via routes such as the Oregon, California, and Mormon Trails. After the end of the Mexican–American War in 1849, vast new American conquests again encouraged mass immigration. Legislation like the Donation Land Claim Act and significant events like the California Gold Rush further encouraged settlers to travel overland to the west.
Water resources management in El Salvador is characterized by difficulties in addressing severe water pollution throughout much of the country's surface waters due to untreated discharges of agricultural, domestic and industrial run off. The river that drains the capital city of San Salvador is considered to be polluted beyond the capability of most treatment procedures.
Guatemala faces substantial resource and institutional challenges in successfully managing its national water resources. Deforestation is increasing as the global demand for timber exerts pressure on the forests of Guatemala. Soil erosion, runoff, and sedimentation of surface water is a result of deforestation from development of urban centers, agriculture needs, and conflicting land and water use planning. Sectors within industry are also growing and the prevalence of untreated effluents entering waterways and aquifers has grown alongside.
The Perris Block is the central block of three major fault-bounded blocks of the northern part of the Peninsular Ranges. The Perris Block lies between the Santa Ana Block to the west and the San Jacinto Block to the east. The Perris Block, was named by Walter A. English in 1925 for the city of Perris, located near the center of the block.
