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According to the United States Census Bureau,〔(US Census Bureau facts )〕 the city has a total area of — of it is land and of it is water. The total area is 3.7 percent water. \iron man coastal plains biome, and its vegetation is classified as temperate grassland. Much of the city was built on marshes, swamp, or prairie—all of which can still be seen in surrounding areas. Much of Houston is very flat, making flooding a recurring problem for its residents. The city stands about 50 feet above sea level—the highest area within city limits being 90 feet.〔(U.S. Coast Guard Air Station–Houston: PCS Section ). ''United States Coast Guard''〕 However, coastal subsidence has caused the elevation to drop 10 feet or more in certain areas. The subsidence was caused by extensive use of ground water and the extraction of oil and natural gas. The city turned to ground-level water sources such as Lake Houston which was created in 1953 and Lake Conroe of which Houston owns two-thirds interest. Houston has four major bayous passing through the city: Buffalo Bayou, which runs into downtown and the Houston Ship Channel; and three of its tributaries: Brays Bayou, which runs along the Texas Medical Center; White Oak Bayou, which runs through the Heights and near the northwest area; and Sims Bayou, which runs through the south of Houston and downtown Houston. The ship channel goes past Galveston and into the Gulf of Mexico. Houston is located east of Austin,〔Lomax, John Nova. "(This Is Texas )." ''Texas Monthly''. February 2013. Retrieved on April 30, 2013. "No, the rightful standard-bearer of our state—the city with the greatest number of people, of cultural happenings, of medical facilities, of gangbuster enterprises—is located 165 miles to the east of Texas’s pink-granite dome." - The first part is discussing Houston. The "pink granite dome" is the Texas State Capitol in Austin.〕 west of the Louisiana border and south of Dallas.〔Martin, Roland. "(Football power in Texas has shifted to Houston )." ''CNN''. January 6, 2012. Retrieved on January 7, 2012.〕 ==Geology== Underpinning Houston's land surface are unconsolidated clays, clay shales, and poorly cemented sands up to several miles deep. The region's geology developed from stream deposits from the erosion of the Rocky Mountains. These sediments consist of a series of sands and clays deposited on decaying organic matter that, over time, transformed into oil and natural gas. Beneath these tiers is a water-deposited layer of halite, a rock salt. The porous layers were compressed over time and forced upward. As it pushed upward, the salt dragged surrounding sediments into dome shapes, often trapping oil and gas that seeped from the surrounding porous sands. This thick rich soil also provides a good environment for rice farming in suburban outskirts that the city continues to grow into near Katy. Evidence of past rice farming is even still evident in developed areas as there is an abundance of rich dark loamy top soil. The Houston region is generally earthquake-free. While the city of Houston contains 86 mapped and historically active surface faults with an aggregate length of 149 miles (240 km),〔(Houston Geographic Description ). ''Diane Moser Properties''〕 the clay below the surface precludes the buildup of friction that produces ground shaking in earthquakes. These faults generally move at a smooth rate in what is termed "fault creep." 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Geography of Houston」の詳細全文を読む スポンサード リンク
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