Look to the west, in the distance you will see one of Padre's natural wonders, Back Island Dune Fields!
Back-Island Dune Field and Fore-Island Blowout Dunes (B10)
Those parts of the fore-island dune ridge that become devegetated naturally or through the actions of man are vulnerable to erosion by the strong southeasterly winds. Sand is blown from the dune ridge over the barrier flat in a northwesterly direction (fig. 90). The result is a blowout dune complex, which may consist of several dune types, including parabolic, transverse, and barchan dunes (fig. 39). Most dune forms change rapidly with changes in wind direction and intensity. The sediment composing these blowout dunes is mostly fine, well-sorted sand derived from fore-island dunes.
Figure 90. Blowout complex that originated at the dune ridge, where stabilizing vegetation had been destroyed, and loose sand was free to blow out (pl. I, grid O-4). Prevailing southeasterlies cause the blowout to migrate across the island in a northwestward direction, although strong north winds modify the complex every winter by blowing much of the sand to the south edge of the barren dune complex (left side in photograph). Several dune forms, depending on wind direction, speed, and duration, occupy the complex at different times. Transverse dunes perpendicular to wind direction dominated this complex at the time the photograph was taken.
As blowout dunes migrate toward the northwest across the barrier flat, they may either become stabilized by grasses or eventually become merged with a back-island dune field. The back-island dune fields are large barren areas of shifting dunes (fig. 91). Barchans and transverse dunes aligned perpendicularly to the wind direction are common in the back-island fields. These relatively small dunes are generally less than 10 feet high. Large (up to 25 feet high), elongate, longitudinal dunes (fig. 51) shift much less readily and may retain their orientations throughout the year. Hunter and others (1972) studied the large dunes on Padre and refer to them as oblique dunes because they are elongate in an east-west direction, or oblique to the net sand transport direction (fig. 49), which is a result primarily of the dominant southeasterlies and the north winter winds. One possible explanation for the relatively stable orientation of these dunes is that they are parallel to one arm of summer barchans and perpendicular to the north winds of winter (Hunter and others, 1972).
Figure 91. Back-island dune field including several large, shifting dunes (pl. I, grid O-19).
In the northern part of the National Seashore, fine sand is supplied to the back-island dune fields by the migrating blowout dunes. The back-island dunes in the southern part, however, are supplied largely by sand reworked from sediments that washed into the back-island area during storms. Presently, neither washovers nor large blowouts occur in the central part of the Seashore; consequently, the back-island area is starved of sand necessary to build large dune fields. What were once dune fields are now patches of vegetated barrier flat fringing the back-island area (for example, grids J-10 through M-10, pl. I).