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Geography of Texas

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The geography of Texas covers a wide and far reaching scope. Occuping about 7 percent of the total water and land area of the U.S.[1], it is the second largest state after Alaska, and is the southernmost part of the Great Plains, which ends in the south against the folded Sierra Madre Oriental of Mexico. Texas is in the south-central part of the United States of America, and is considered to form part of the U.S. South and also part of the U.S. Southwest.

The Rio Grande, Red River and Sabine River all provide natural state lines where Texas borders Oklahoma on the north, Louisiana and Arkansas on the east, and New Mexico and the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas to the south. Austin, the state capitol is farther south than all other US state capitals except Honolulu.[2]

By residents, the state is generally divided into North Texas, East Texas, Central Texas, South Texas, and West Texas, but according to the Texas Almanac, Texas has four major physical regions: Gulf Coastal Plains, Interior Lowlands, Great Plains, and Basin and Range Province. This has been cited as the difference between human geography and physical geography, although the fact that Texas was granted (and retains to this day) the perogative to divide into as many as five U.S. states may be a historical motive for Texans defining their state as containing exactly five regions.[3]

Some regions of Texas are associated with the South more than the Southwest (primarily East Texas), while other regions share more similarities with the Southwest than the South (primarily West Texas and South Texas). Even the northwestern part of the state seems to have more in common with parts of the United States (Kansas and Nebraska) that are considered "midwestern" and never "southern". The size of Texas prohibits easy categorization of the entire state wholly in any recognized region of the United States; geographic, economic, and even cultural diversity between regions of the state preclude treating Texas as a region in its own right.

Climate

Texas rivers map showing Captain Marcy's route though Texas in 1854.

Continental, Mountain, and Modified Marine are the three major climatic types of Texas, with no distinguishable boundaries. Modified Marine, or subtropical, dominates the majority of the state.[4] Texas has an annual precipitation range from 60.57 inches in Jasper County, East Texas, to 9.43 inches in El Paso. The record high of 120°F was reached at Seymour on Aug. 12, 1936, and Monahans on June 28, 1994. The low also ties at -23°F in Tulia on Feb. 12, 1899, and Seminole on Feb. 8, 1933.[5]

Most of Texas is under direct threat from drought, heat, hail, high winds, flash floods, hurricanes, and tornados. Select areas occasionaly suffer from dust storms, river floods, snow and ice.[6] Amarillo has the highest average wind speed in Texas at 14.3 mph.[7]

Physical geography

With 10 climatic regions, 14 soil regions, and 11 distinct ecological regions, classifing regions becomes problematic with differences in soils, topography, geology, rainfall, and plant and animal communities.[8] The geographic center of Texas is about 15 miles northeast of Brady in northern McCulloch County. Guadalupe Peak, at 8,749 feet above sea level is the highest point in Texas. The lowest being sea level where Texas meets the Gulf of Mexico.[9] Texas has five state forests and 120 state parks for a total over 605,000 acres.[10] There are 3,700 named streams and 15 major river systems flowing through 191,000 miles of Texas. Eventually emptying into seven major estuaries, these rivers support over 212 reservoirs. [11]

Texas is so large in its east-west expanse that El Paso, in the western corner of the state, is closer to San Diego, California than to Beaumont, near the Louisiana state line; Beaumont, in turn, is closer to Jacksonville, Florida than it is to El Paso. Also, Texarkana, in the northeastern corner of the state, is about the same distance from Chicago, Illinois as it is to El Paso. The north-south expanse is similarly impressive; Dalhart, in the northwestern corner of the state, is closer to the state capitals of Kansas, Colorado, New Mexico, Oklahoma and Wyoming than it is to Austin, its own state capital.[12]

Gulf Coastal Plains

Caddo Lake

The Gulf Coastal Plains from the Gulf of Mexico inland to the Balcones Fault and the Eastern Cross Timbers. This large area stretches from the cities of Paris to San Antonio to Del Rio but shows a large variety in vegetation. The thick pineywoods of east Texas and the brush country south of San Antonio are found here. With 20 - 50 inches annual rainfall, this is a nearly level, drained plain dissected by streams and rivers flowing into estuaries and marshes. Windblown sands and dunes, grasslands, oak mottes and salt marshes make up the seaward areas.[13] National Parks include Big Thicket National Preserve, Padre Island National Seashore and the Palo Alto Battlefield National Historic Site.[14]

Interior Lowlands

Looking north at the Caprock Escarpment.

The Interior Lowlands are bounded by the Caprock Escarpment to the west, the Edwards Plateau to the south, and the Eastern Cross Timbers to the east. This area includes the North Central Plains around the cities of Abilene and Wichita Falls, the Western Cross Timbers to the west of Fort Worth, the Grand Prairie, and the Eastern Cross Timbers to the east of Dallas. With 35 - 50 inches annual rainfall, gently rolling to hilly forested land is part of a larger pine-hardwood forest of oaks, hickories, elm and gum trees.[13] Soils vary from coarse sands to tight clays or red-bed clays and shales.[15] The only National Park in this region is Lake Meredith National Recreation Area.[14]

Great Plains

Hill Country

The Great Plains include the Llano Estacado, the Panhandle, Edwards Plateau, Toyah Basin, and the Llano Uplift. It is bordered on the east by the Caprock Escarpment in the panhandle and by the Balcones Fault to the southeast. Cities in this region include Austin, San Angelo, Midland and Odessa, Lubbock, and Amarillo. The Hill Country is a popular name for the area of hills along the Balcones Escarpment and is a transitional area between the Great Plains and the Gulf Coastal Plains. With 15 - 31 inches annual rainfall, the southern end of the Great Plains are gently rolling plains of shrub and grassland, and home to the dramatic Caprock Canyons and Palo Duro Canyon state parks.[13] The largest concentration of playa lakes in the world (nearly 22,000) is on the Southern High Plains of Texas and Eastern New Mexico.

Texas' Blackland Prairie were some of the first areas farmed in Texas. Highly expansive clays with characteristic dark coloration, called the Houston Black series, occur on about 1.5 million acres extending from north of Dallas south to San Antonio. The Professional Soil Scientists Association of Texas has recommended to the State Legislature that the Houston Black series be designated the State soil. The series was established in 1902.[16] National Parks in this area are the Lyndon B. Johnson National Historical Park and the San Antonio Missions National Historical Park.[14]

Basin and Range Province

El Capitan
Rio Grande Valley

Trans-Pecos Natural Region with less than 12 inches annual rainfall. The most complex Natural Region, it includes Sand Hills, the Stockton Plateau, desert valleys, wooded mountain slopes and desert grasslands. The Basin and Range Province in extreme western Texas, west of the Pecos River beginning with the Davis Mountains on the east and the Rio Grande to its west and south. The Trans-Pecos region is the only part of Texas regarded as mountainous and includes seven named peaks in elevation greater than 8,000 feet (2,400 m). With less than 12 inches annual rainfall, this region includes sand hills, desert valleys, wooded mountain slopes and desert grasslands.[13] The vegetation diversity includes at least 268 grass species and 447 species of woody plants.[17] National Parks include the Amistad National Recreation Area, Big Bend National Park, Chamizal National Memorial, Fort Davis National Historic Site, Guadalupe Mountains National Park, and the Rio Grande Wild and Scenic River.[14]

Geology

Main article: Geology of Texas
File:TXSeaWIFS1.jpg
SeaWIFS satellite image looking east over the southern United States, showing the location of Dallas and Fort Worth

Texas is mostly sedimentary rocks, with east Texas underlain by a Cretaceous and younger sequence of sediments, the trace of ancient shorelines east and south until the active continental margin of the Gulf of Mexico is met. This sequence is built atop the subsided crest of the Appalachian Mountains–Ouachita Mountains–Marathon Mountains zone of Pennsylvanian continental collision, which collapsed when rifting in Jurassic time opened the Gulf of Mexico. West from this orogenic crest, which is buried beneath the Dallas–Waco–Austin–San Antonio trend, the sediments are Permian and Triassic in age. Oil is found in the Cretaceous sediments in the east, the Permian sediments in the west, and along the Gulf coast and out on the Texas continental shelf. A few exposures of Precambrian igneous and metamorphic rocks are found in the central and western parts of the state, and Oligocene volcanic rocks are found in far west Texas, in the Big Bend area. A blanket of Miocene sediments known as the Ogallala formation in the western high plains region is an important aquifer. Texas has no active or dormant volcanoes and few earthquakes, being situated far from an active plate tectonic boundary. (The Big Bend area is the most seismically active; however, the area is sparsely populated and suffers minimal damages and injuries, and no known fatalities have been attributed to a Texas earthquake.)

Resources

With enormous natural resources, Texas is a major agricultural and industrial state. It leads all other states in such categories as oil, cattle, sheep, and cotton. Texas also produces poultry, eggs, dairy products, greenhouse and nursery products, wheat, hay, rice, sugar cane, and peanuts, and a range of fruits and vegetables. [18]

  • Asphalt-bearing rocks, mainly cretaceous limestones, occur in Bexar, Burnet, Kinney, Uvalde, and other counties.
  • Deposits of barite are widely distributed in Texas, but most are minor.
  • Cement is currently produced in Bexar, Comal, Dallas, Ector, Ellis, El Paso, Harris, Hays, McLennan, Nolan, Nueces, Potter, and Tarrant counties. Historically, Texas' portland cement output accounts for about 10 percent of the annual United States production.
  • With an abundance of various types of clays, Texas is one of the leading producers of clays.
  • Bituminous coal occurs primarily in Coleman, Eastland, Erath, Jack, McCulloch, Montague, Palo Pinto, Parker, Throckmorton, Wise, and Young counties of Texas. Lignite, or brown coal, occurs in deposits in the Texas Coastal Plain.
  • Copper deposits in Texas occur in the Trans-Pecos region, in north central Texas, and in the Llano region. Most of the state's small production has been from the Van Horn-Allamoore mining district, whereas only small shipments of copper have been reported from the North Texas and Llano regions.
  • Fluorspar or fluorite is an important industrial mineral used in the manufacture of steel, aluminum, glass, and fluorocarbons. It occurs at several localities in the Trans-Pecos and Llano regions of Texas.
  • Collecting gemstone rock and mineral specimens has proved quite profitable. Agate, jasper, cinnabar, fluorite, topaz, calcite, opal, petrified wood, and tektites are all commonly collected.
Shaded Relief Map of the Llano Estacado.
  • Deposits of graphite occur in the Llano region and was previously produced in Burnet County.
  • Bat guano occurs in numerous caverns in the Edwards Plateau and in the Trans-Pecos region and to a more limited extent in Central Texas.
  • Gypsum is extensively developed in Texas where the main occurrences are in the Permian Basin, the Cretaceous Edwards Formation in Gillespie and Menard counties, and the Gulf Coast salt domes of Harris County and previously Brooks County.
  • Texas is the leading producer of helium solely from the Cliffside gas field near Amarillo.
  • Deposits of iron ore are present in northeastern Texas as well as several in Central Texas.
  • Limestones, abundant in many parts of Texas, are utilized in the manufacture of lime. Plants for the production of lime are currently operating in Bexar, Bosque, Burnet, Comal, Deaf Smith, Hill, Johnson, Nueces, and Travis counties.
  • Magnesium chloride, magnesium sulfate and other mineral salts are present in the Upper Permian basin and in the underlying playas of the High Plains.
  • Manganese is known to occur in Precambrian rocks in Mason and Llano counties, in Val Verde County, in Jeff Davis County, and in Dickens County.
  • Mercury mineral deposits occur in southern Brewster and southeastern Presidio counties, where mining was initiated in 1896. With all of the mines closed in the early 1970s, no production has been reported since 1973.
  • Mica is present in Precambrian pegmatite in the Llano region.
  • Common opal occurs on the Texas Coastal Plain.
  • Oyster and clam shells occur bordering the Gulf of Mexico and in some sediments along the Texas Coastal Plain. Shells were extensively produced until the early 1960s, when production was discontinued because of environmental issues.
  • Elements of the Lanthanide series are commonly termed rare-earth elements. Several of the rare earths have anomalous concentrations in the rhyolitic and related igneous rocks in the Trans-Pecos area of Texas. A deposit containing several rare-earth minerals was exposed at Barringer Hill in Llano County before it was covered by the waters of Lake Buchanan.
  • Salts occurs in large quantities in salt domes in the Texas Coastal Plain and with other evaporites in the Permian Basin of West Texas, as well as near Grand Saline, Texas.
  • Sands used for industrial purposes commonly have been found in the Texas Coastal Plains, East Texas, north central Texas, and Central Texas.
  • The discovery of silver in Texas has been credited by some to Franciscans who discovered and operated mines near El Paso about 1680. Documented silver production started in the late 1880s at the Presidio Mine, in Presidio County. Texas produced 32,663,405 troy ounces of silver between 1885 and 1955
  • Materials suitable for dimension stone or building stone, can be found in most parts of the state except the High Plains and the Gulf Coastal Plains. Granite, limestone, and sandstone are currently the only stones being produced.
  • Sulfur occurs in the caprocks of salt domes in the Gulf Coastal Plain, in Permian-age bedded deposits in Trans-Pecos Texas.
  • In the past uranium was produced from surface mines in Atascosa, Gonzales, Karnes, and Live Oak counties. All uranium mines are closed and Texas is no longer a producer.[19]

See also

References

Wikimedia Commons has media related to Texas.
  1. ^ "Tx Almanac". Retrieved 2006-08-01.
  2. ^ "Netstate". Retrieved 2006-07-11.
  3. ^ "Texas Escapes.com". Retrieved 2006-07-15.
  4. ^ "The Office of the State Climatologist". Retrieved 2006-07-14.
  5. ^ "Tx Almanac". Retrieved 2006-07-11.
  6. ^ John Nielsen-Gammon (2004-04-01). "Greatest Hits". Retrieved 2006-07-14. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  7. ^ "Texas Climate". Retrieved 2006-07-14.
  8. ^ "Tx Envionmental Profiles". Retrieved 2006-07-14.
  9. ^ "Netstate". Retrieved 2006-07-11.
  10. ^ "About.com". Retrieved 2006-07-11.
  11. ^ "Tx Parks and Wildlife". Retrieved 2006-07-14.
  12. ^ "StateMaster". Retrieved 2006-07-11.
  13. ^ a b c d "LoneStarInternet". Retrieved 2006-07-14.
  14. ^ a b c d "Tx Environmental Profiles". Retrieved 2006-07-14.
  15. ^ "NPAT Region 8". Retrieved 2006-07-17.
  16. ^ "USDA Houston Black" (PDF). Retrieved 2006-07-14.
  17. ^ "Tx Parks and Wildlife". Retrieved 2006-07-14.
  18. ^ "infoplease.com". Retrieved 2006-07-14. {{cite web}}: Cite has empty unknown parameters: |accessyear=, |month=, |accessmonthday=, and |coauthors= (help)
  19. ^ Garner, L. Edwin. "The Handbook of Texas online". Retrieved 2006-07-11.
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