Dallas, Texas

Dallas is the third-largest city within the State of Texas, ninth in the United States, and together with Fort Worth and the Mid-Cities form the largest metropolitan economic area in the south-central United States. As of the 2000 U.S. Census, Dallas had a total population of 1.1 million (est. as of July 1, 2004 at 1,210,393). Dallas is the county seat of Dallas County. A small portion of the city also extends into the neighboring counties of Collin County, Denton County, Kaufman County, and Rockwall County.

Geography and climate

According to the United States Census Bureau, the city has a total area of 997.1 km² (385.0 mi²). 887.2 km² (342.5 mi²) of it is land and 110.0 km² (42.5 mi²) of it is water. The total area is 11.03% water. These statistics are only for the city of Dallas proper. In fact, Dallas is a small part of the much larger urbanized area called the Dallas-Fort Worth Metroplex. About one in every four Texans lives in the DFW metroplex.

Related Topics:
United States Census Bureau - Km² - Mi²

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Dallas, and its surrounding area, is mostly flat and lies at an elevation ranging from 450 to 550 feet (140 to 170 m). The western edge of the "Austin Chalk" formation, a limestone escarpment, rises 200 feet (60 m) and runs roughly north-south through Dallas County. The uplift is particularly noticeable in the neighborhood of Oak Cliff and the cities of Cockrell Hill and Cedar Hill.

Related Topics:
Limestone - Oak Cliff - Cockrell Hill - Cedar Hill

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The Trinity River is a major Texas waterway that passes from the northwest right by the southern portion of downtown Dallas as it heads southeast to Houston. The river is flanked on both sides with a 50 foot (15 m) earthen levee to keep that part of the city from flooding. Several bridges traverse the river connecting southern Dallas to downtown Dallas. Businesses and businessmen, like Ross Perot, Jr., have pushed in recent years to build a multi-million-dollar, landmark bridge over the river and convert that section of the river into a park area with nearby commercial and retail services somewhat similar to the River Walk in San Antonio or Townlake in Austin. Some proponents claim this development would bring more life, commerce, revenue and lower crime to downtown Dallas and poorer, southern Dallas. Some critics charge the project is a facade to serve special, financial interests of businessmen. Residents barely approved a bond proposal in 1998 to fund the Trinity River Project and work has progressed slowly towards implementing it. Ron Kirk, Dallas' first African American mayor, championed the project during his term as mayor as he did the new American Airlines Center in downtown. His successor, mayor Laura Miller—sometimes referred to as Dallas' first reform mayor—won the vacancy left by Kirk when he ran unsuccessfully for the U.S. Senate. Miller won in part based on her platform she would focus on the city's basic needs like roads and other infrastructure and city employees' pay; services some claimed were neglected at the cost of special projects like the American Airlines Center.

Related Topics:
Trinity River - Houston - River Walk - San Antonio - Austin - 1998 - Trinity River Project - Ron Kirk - African American - American Airlines Center - Laura Miller

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White Rock Lake is Dallas's other significant water feature. The lake and surrounding park is a popular destination in the Lakewood/Casa Linda neighborhoods for boaters, joggers, bikers, skaters and for related activities. The lake also boasts the 66 acre (270,000 m²) Dallas Arboretum and Botanical Garden on its shore. Bachman Lake, just northwest of Love Field, is a smaller lake and surrounding park that is also used for recreation.

Related Topics:
White Rock Lake - Arboretum - Bachman Lake

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Dallas lies near the bottom of a tornado region that runs through the prairie lands of the midwest. In the spring, cool fronts moving from Canada collide with warm, humid air streaming in from the Gulf Coast. When these fronts meet over Dallas, severe storms are generated with spectacular lightning shows, torrents of rain, large hail and, at times, tornadoes.

Related Topics:
Prairie - Midwest - Canada - Gulf Coast

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Geology

North Texas sits near the edge of the North American craton of Precambrian age. The oldest rocks in Texas date from the Mesoproterozoic, about 1600 million years old. The greater Dallas-Fort Worth metroplex sits on gently tilted sediments. The region west of Weatherford, Texas consists of Pennsylvanian sediments that tilt a few degrees west. These sediments were deformed when Gondwana collided with Laurasia to form Pangea about 300 million years ago (Ma). A great mountain range formed, the Marathon-Ouachita-Appalachian-Variscan cordillera. This collapsed during the Triassic and Jurassic to form the Atlantic Ocean-Gulf of Mexico basin. Sea level rose as the supercontinent Pangea broke up. The Pennsylvanian mountains of DFW were eroded for about 190 million years until the mountains were worn down.

Related Topics:
North American craton - Precambrian - Sediments - Weatherford, Texas - Pennsylvanian - Gondwana - Laurasia - Pangea - Marathon - Ouachita - Appalachian - Variscan - Triassic - Jurassic - Atlantic Ocean - Gulf of Mexico - Supercontinent

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The DFW metroplex sprawls across a 100km wide N-S trending belt of Cretaceous sediments. Fort Worth in the west is neatly built on Early Cretaceous (Comanche Series) and Dallas in the east is built on Late Cretaceous (Gulf Series) sediments. DFW lay on the beach about 110 Ma, during early Cretaceous time. The water kept rising for another 30-50 million years, so that by the time the coccolithophorid Austin chalk was deposited, the "Octopus Garden" that became DFW lay 100m or more below the sea surface. The inexorable rise in sealevel was only interrupted by tectonic rumblings in southern Arkansas and Oklahoma, shedding copious amounts of Woodbine Sandstone to the south. These sandstones underlie the cities of Denton, Grapevine, and Arlington, Texas. The Cretaceous sediments dip a degree or so the east, so the Cretaceous sediments get younger towards the east. Sediments deposited during the Cretaceous-Tertiary extinction event, when the dinosaurs were killed, lie near the town of Terrell, at the eastern edge of the DFW metroplex.

Related Topics:
Cretaceous - Fort Worth - Early Cretaceous - Late Cretaceous - Chalk - Woodbine Sandstone - Denton - Grapevine - Arlington, Texas - Cretaceous-Tertiary extinction event - Dinosaurs - Terrell

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People enjoy searching for fossils in the rocks around Dallas. Remnants of dinosaurs and Late Cretaceous marine reptiles such as Mosasaur are found.

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The Trinity River has been important in shaping the DFW metroplex. Dallas was situated at the best ford, downstream from where the Elm Fork joins the main stream, where the river flows SE over the chalk. This provided a place where travellers need only cross the river once, at a place with relatively firm landings and bottoms. This was the best place to cross the Trinity from the earliest days, best for fordings, ferries, and bridges. During the days of the Republic of Texas, the DFW metroplex was mostly uninhabited by Europeans, but settlers began to find their way N in the 1840's. The route north naturally followed the low hills and gentle ridges of Austin chalk hills to the river ford that soon became Dallas. The future site of Dallas was selected by Bryan as the place for his trading post to overlook the ferry that he operated at the crossing.

Related Topics:
Trinity River - Republic of Texas

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Dallas was also affected subtly by much younger geologic formations related to an older, more vigorous Trinity River. Changing Pleistocene-Holocene climate had two effects on the Trinity River: It caused downcutting (few people know that there is a 100m-deep buried canyon beneath the Trinity in Dallas) and a wetter climate caused much more water to flow in the river. The greater river flow generated great sedimentary terraces. From time to time these terrace deposits reveal bones of extinct giant mammals, such as Mastodons and Mammoths. The Pleistocene terraces affected the development of Dallas, providing a rich alluvial soil and a perched aquifer, very useful indeed during the early years. Downtown Dallas is built on a series of these terraces, rising subtly eastward from the Trinity river.

Related Topics:
Pleistocene - Holocene - Terrace - Mastodons - Mammoths - Aquifer

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The DFW meroplex had an additional, if subtle, geologic advantage. The Trinity is not good for navigation by boats but is great for drinking. Trinity River water is better than either of the larger rivers to the north and south, the Red River and the Brazos River. The larger rivers are longer and flow over salt-bearing Permian sediments, well west of the Trinity headwaters. The Trinity is consequently sweeter water than either the larger Brazos or Red rivers. Life was better near sweet water, and this simple fact helped DFW prosper relative to settlements on the larger rivers to the north and south. Because the Trinity is not suitable for navigation, Dallas could not have grown to be a large city until the railroad arrived, which happened early in Dallas' history, in the early 1870's. Dallas is thus truly a modern city, because it could not have grown so large until mechanical transportation systems made the Trinity disadvantage in river navigation insignificant.

Related Topics:
Red River - Brazos River - Permian - Sediments

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Climate

Dallas gets about 30 inches (760 mm) of rain per year, much of which is delivered in the spring time. The climate of Dallas is classified a humid subtropical climate, yet this part of Texas also tends to get hot, dry winds from the north and west in the summer. In the winter, the winds are cool, which can cause the region to fall below freezing occasionally. A few inches of snow for a day or two falls about once each winter, and about every other winter the cool air from the north and the humid air from the south lead to freezing rain, which usually causes the city to come to a screeching halt for a day or two if the roads and highways become dangerously slick. Regardless, winters are relatively mild compared to the Texas Panhandle and other states to the north. Dallas winters are occasionally interspersed with Indian summers.

Related Topics:
Humid subtropical climate - Indian summer

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Spring and fall and the pleasant, moderate temperatures accompanying those seasons are somewhat short-lived in Dallas. However short the season is, residents and visitors appreciate the beauty of the vibrant wildflowers (such as the bluebonnet, Indian paintbrush and other flora) which bloom in spring and are planted around the highways throughout Texas. In the spring the weather can also be quite volatile and change quickly in a matter of minutes. The cliché about volatile climates popular in various parts of the US—"if you don't like the weather, wait a little while and it'll change"—applies well to Dallas' spring weather. Many consider autumn, around late September and October, to be the best time to visit the Metroplex. Yet many events are also scheduled for the more volatile season of spring.

Related Topics:
Bluebonnet - Indian paintbrush - Flora

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The USDA rates the city of Dallas as being part of Zone 8.

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Ongoing comparisons are made between Dallas' summer weather and Houston's. Texans generally agree Houston is significantly more humid and Dallas is slightly hotter, although given Houston's humidity it may have a higher heat index than Dallas.

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