LOCATION: Houston, seat of Harris County, Texas, is located on the upper Gulf coastal plain at 9522' West and 2946' North, 50 miles from the Gulf of Mexico.
AREA: The Houston-Galveston-Brazoria Consolidated Metropolitan Statistical Area (CMSA) consists of three Primary Metropolitan Statistical Areas (PMSAs): Houston (Chambers, Fort Bend, Harris, Liberty, Montgomery, and Waller Counties), Galveston-Texas City (Galveston County), and Brazoria (Brazoria County). For convenience, the longer titles are shortened to "Houston CMSA" and "Galveston PMSA."
Houston CMSA 8,778.34 sq.mi.
Houston PMSA 6,304.31 sq.mi.
Harris County 1,777.89 sq.mi.
City of Houston 594.13 sq.mi.
Brazoria PMSA 1,597.54 sq.mi.
Galveston PMSA 876.46 sq.mi.
The City of Houston lies in three counties: Harris (583.450 sq.mi.), Fort Bend (8.080 sq.mi.), and Montgomery (2.598 sq.mi.). Harris County contains part or all of 35 incorporated areas.
Under Texas' Municipal Annexation Act of 1963, cities have certain powers over surrounding unincorporated areas, termed the Extraterritorial Jurisdiction. ETJ is a function of population; for cities over 100,000, it can cover all unincorporated area within five miles of any point on the city limits. Houston's ETJ encompasses 1,311.950 sq.mi., excluding the area of cities that lie within it.
TOPOGRAPHY: Houston lies largely in the northern portion of the Gulf coastal plain, a 40- to 50-mile-wide swath along the Texas Gulf Coast. Typically, elevation rises approximately one foot per mile inland.
Northern and eastern portions of the area are largely forested; southern and western portions are predominantly prairie grassland; coastal areas are prairie and sand.
Surface water in the Houston region consists of lakes, rivers, and an extensive system of bayous and manmade canals that are part of the rainwater runoff management system. Some 25%-30% of Harris County lies within the 100-year flood plain. Elevation ranges (a.s.l.): Brazoria 0'-146', Chambers 0'-85', Fort Bend 12'-158', Galveston 0'-43', Harris 0'-310', Liberty 0'-269', Montgomery 43'-435', Waller 80'-357'.
GEOLOGY: Underpinning Houston's land surface are unconsolidated clays, clay shales, and poorly-cemented sands extending to depths of several miles. 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, was 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.
The Houston region is earthquake-free. While the City of Houston contains 86 mapped and historically active surface faults with an aggregate length of 149 miles, the clay below the surface precludes the buildup of friction that produces ground shaking in earthquakes. These faults move only very gradually in what is termed "fault creep."