page_title: Padre Island
section_title: Geology
hierarchical_section_title: Padre Island / Geology
caption_attribution_description: Photos and maps related to Padre Island. Padre Island National Seashore - sand dunes
context_page_description: Padre Island is the largest of the Texas barrier islands and the world's longest barrier island. The island is located along Texas's southern coast of the Gulf of Mexico and is noted for its white sandy beaches. Meaning father in Spanish, it was named after Father José Nicolás Ballí, who owned the island and served as a missionary priest and collector of finances for all the churches in the Rio Grande Valley. He also founded the first mission in present-day Cameron County.
  Padre Island is the second-largest island by area in the contiguous United States, after Long Island in New York on the Atlantic Coast. It is about 113 miles long and 1.8 miles wide, stretching from the city of Corpus Christi, in the north, to the resort community of South Padre Island in the south. The island is oriented north-south, bordered by the Gulf of Mexico on the east and Laguna Madre on the west. The island's northern end connects to Mustang Island by roadway. The southern end of the island is separated from Brazos Island by the Brazos Santiago Pass.
  The town of South Padre Island is located on its southern end, but the island as a whole is sparsely populated.
context_section_description: Geologically speaking, Padre Island is a young island, having formed in just the last several thousand years. It is one of 300 barrier islands stretching from Maine to Mexico. These natural barrier islands act to protect the mainland from the direct onslaught of storms.
  Padre Island began forming as a submerged sand bar some 4500 years ago, as shown by radiocarbon dating of shells. Geologic speculation indicates the emerged island may be 1000 to 1500 years younger.  Barrier island origins have been debated for many years by geologists, but it is agreed they are formed and modified by such factors as sediment type and supply, sea-level directional changes, current and wave strength and direction, and tide magnitude.
  It is theorized that Padre Island formed from offshore shoals, with later growth aided by spit accretion. (A spit is a long, narrow tongue of sand extending from a mainland shoreline and formed by the shoreline drifting of sediments.) After a history of shifting, abandonment and reestablishment by storm breaches, many tidal inlets were slowly closed. Short islands were joined to form today's longer islands.
  Padre Island graphically illustrates the life and sequences of a barrier shoreline: accretionary or building phase, equilibrium or stability phase, and erosion or destructional state. The northern half of Padre Island's shoreline is in equilibrium; the southern half (and much of the remaining Texas coastline) is in an erosional stage. Wind, wave and current action continue to rework and shape the island. South Padre Island has been in a destructive phase for a long time, probably having retreated landward (along with the lagoon and mainland shoreline).
  All of Padre Island will probably retreat landward through long-term erosion due to three causes: interruption and decrease in sediment supply, relative sea level rise, and tropical storm activity. Today, hurricane washovers and wind-carried sand deposited in Laguna Madre build Padre Island's landward side at the expense of Laguna Madre.
caption: Padre Island sand dunes at sunset
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