Padre Island National Seashore             

Geology

Because the island is formed almost entirely out of sand, the park has a small collection of geological specimens, most of which are samples of the island sand/soil, but the collection also contains a few rare or intriguing items. 

The rare items are mostly fulgurite, which is a rock that forms when lightning strikes sand and fuses it together into a column.  Because lightning usually strikes the tallest object in an area and because the tallest objects on the island are sand dunes, fulgurite may be found at the tops of dunes.  Normally, fulgurite is only an inch or two across, but the park's museum contains a few pieces which are about four inches in diameter and thus exceptionally rare.  They are not pictured below.

The park also has a small collection of sand roses, also known as "desert roses".  These are rosettes made when the water table fluctuates.  The water changes calcium sulfate (CaSO4) in the sand into gypsum crystals which grown and entrap sand grains.  Every time the water table advances and retreats, it creates a new layer of crystals and entrapped sand on a sand rose. Sand roses are found worldwide and can be immense.  Some of those in Saudi Arabia can be three feet or more across while some clusters of sand roses can be as big as a room.

Shown here are only a few samples of both.  More photos may be added at a later date.

For more information on the geology of Padre Island, follow this link to the NPS Geologic Resources Division webpage on Padre Island or follow this link to an NPS webpage on coastal materials.

Fulgurite

Desert Roses

Although only one is pictured with a ruler, all are approximately the same size. 

None are over four inches across.

Send an e-mail to the Virtual Museum Curator via PAIS_Museum@nps.gov.

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