Basalt fan structure
Rock formation
![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/24/Columnar_basalt_Sudurarhraun.jpg/220px-Columnar_basalt_Sudurarhraun.jpg)
A basalt fan structure is a basalt formation composed of columnar jointed basalt columns that have slumped into a fan shape.[1]
Such formations are most likely created when basalt lava is intruded into a soft material, such as loose volcanic ash, which is unable to support the intrusion. As the basalt cools and forms columns, the ash collapses, causing the lava spread and form a fan shape. The formations can be vertical or any degree of horizontal.[citation needed]
References
- ^ Faust, George T. "Joint Systems in the Watchung Basalt Flows, New Jersey" (PDF). Geological Survey Professional Paper 864-B. United States Government Printing Office. Retrieved 17 December 2019.
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