|WikiProject Volcanoes||(Rated Start-class, Mid-importance)|
|WikiProject Geology||(Rated Start-class, Mid-importance)|
Devils Tower, USA
Is the Devils Tower a volcanic plug? The National Park Service of the U.S. Department of the Interior wrote here:
Other theories have suggested that Devils Tower is a volcanic plug or that it is the neck of an extinct volcano (an unlikely theory, for there is no evidence of volcanic activity - volcanic ash, lava flows, or volcanic debris - anywhere in the surrounding countryside)!
- The feature is almost certainly a laccolith-the remains of an ancient intrusive flow of magma into the earth's crust millions of years ago.The surrounding rock is all sedimaentary and at one time would have been higher than the Tower. Erosion was caused by -almost certainly -at the end of the last ice age which released a mammoth flood of melt water through modern central USA-the central plains. The old intrusive flow is much harder and resisted rapid erosion thus standing up above the modern landscape. There are many of these features in the USA. — Preceding unsigned comment added by 18.104.22.168 (talk) 22:28, 1 November 2011 (UTC)
Reference footnotes for Sigiriya paragraph not working.
I couldn't figure out the formatting used by the editor, and so could not fix them.
"Sigiriya, or the Lion's Rock or the Lion's Mountain, is a hardened magma volcanic plug formed from an extinct and long-eroded volcano."
I've seen this being repeated on several places in the internet, but there is no primary source to back up this claim. For example this paper on the geology of Sri Lankan archaeological sites (including a section on Sigiriya) does not mention an extinct volcano or a volcanic plug.