Editing Padre Island National Seashore (section)

==Geology==
The geology of Padre Island National Seashore doesn't just belong within the park itself. PAIS is part of the world's longest natural [[barrier bar]] system. Padre Island is a very young geological feature that only developed merely 4,500 to 5,000 years ago, according to [[radio carbon dating]] of shells.<ref>{{cite web| url = http://www.nps.gov/history/history/online_books/pais/1980-17/sec2.htm| url-status = dead| archive-url = https://web.archive.org/web/20070830024422/http://www.nps.gov/history/history/online_books/pais/1980-17/sec2.htm| archive-date = 2007-08-30| title = Texas Bureau of Economic Geology: Padre Island National Seashore: A Guide to the Geology, Natural Environments, and History of a Texas Barrier Island (Origin and Geologic History of Padre Island)}}</ref>

===General physiography===
Geologically extremely young, Padre Island is a vastly [[wikt:dynamic|dynamic]] geologic feature. Unlike most of today's geologic features, such as the [[Grand Canyon]], Padre Island changes constantly. Situated in a stable [[Sedimentary basin|depository basin]], there isn't much that can intervene with the barrier bars, except for the occasional hurricanes that come by. Most of Padre Island is less than 20 feet above mean sea level. Constant bombardment of prevailing southeasterly winds from the [[Gulf of Mexico]] heap beach of sand into high foredunes. In some places, the onshore wind may blow loose sand from the foredunes and beach across the flats beyond. Active sand dunes march across the island, smothering vegetation in their paths and leaving barren sandflats in their wakes. In other places, vegetation may win a battle of its own and stabilize the blowing sand by binding it with roots and vines. Slower daily movements of the sand and stabilizing effects of vegetation are interrupted occasionally by the brutal force of hurricane winds, waves, and tides. During storms, beaches are eroded, vegetation is ripped up, dunes are flattened, and channels are scoured across the island.<ref>{{cite web| url = http://www.nps.gov/history/history/online_books/pais/1980-17/intro.htm| url-status = dead| archive-url = https://web.archive.org/web/20070903025541/http://www.nps.gov/history/history/online_books/pais/1980-17/intro.htm| archive-date = 2007-09-03| title = Texas Bureau of Economic Geology: Padre Island National Seashore: A Guide to the Geology, Natural Environments, and History of a Texas Barrier Island (Introduction)}}</ref>

====Laguna Madre====
[[Laguna Madre (United States)|Laguna Madre]], separating Padre Island from the [[Texas]] mainland, is locked in by the barrier [[island]]. Consequently, circulation of [[seawater]] in and out of the [[lagoon]] is highly restricted. The combination of a high rate of [[evaporation]] under the hot Texas sun and little mixing with either freshwater or normal seawater has made Laguna Madre extremely salty.

The maximum width of the lagoon is approximately 10 miles. In many places, however, lagoon width fluctuates considerably with the height of [[Tides|wind-generated tides]]. The lagoon is widest during highest wind tides, which produce maximum flooding of the vast tidal flats.

Like the island environments, the environments of Laguna Madre vary considerably. Within the national seashore, the northern part of the lagoon is occupied largely by grassflats having an average water depth of about 3 feet. These grassflats are environments of very high biologic activity, serving as spawning grounds for a number of fish, clams, and snails.

The shallowest parts of the lagoon lie in the central part of the national seashore. These areas are known as Middle Ground and the Land-Cut Area, where the Intracoastal Waterway was dredged through the rarely flooded wind-tidal flats (pl. I). The Hole, which lies between Middle Ground and the Land-Cut Area, is not really much of a hole; its average depths are only 1 to 2 feet. This "hole" is occupied mostly by flats supporting shoalgrass and algae. The deepest parts of the lagoon are south of the Land-Cut Area, where the muddy sand bottoms lie at depths as great as 8 feet.

Two small natural islands in Laguna Madre are unique environments within the national seashore. North and South Bird Islands, each a series of [[Berm|sand berms]] or ridges, have become important bird rookeries. Some of the man-made spoil islands along the [[Intracoastal Waterway]] are also nesting grounds for a variety of birds.

<gallery mode="packed" heights="150px">
File:Padre Island National Seashore, dunes, Kleberg Co, TX; 1 Nov 2022.jpg|Sand dunes and wildflower at beach (Nov 2022)
File:Padre Island National Seashore, grassland, Kleberg Co, TX; 31 Oct 2022.jpg|Interior island grassland (Oct 2022)
File:Padre Island National Seashore, interior island dunes, Kleberg Co. TX; 2 Nov 2022.jpg|Interior island dunes (Nov 2022)
File:Padre Island National Seashore, freshwater pond, Kleberg Co, TX; 1 Nov 2022.jpg|A freshwater pond (Nov 2022)
</gallery>