, one of the largest geological structures in the world are the Siberal Traps, where huge but successively smaller volcanic outflows
produced circular "steps" that can be seen by astronauts.
trap rocks can be seen all over the world. 'the devil's stairway (in Ulster, Norther Ireland), the Palisades of NY/NJ, and so on..
and the steps are not circular, but hexagons, (they are realy giant crystal structures, and a very strong stable compound (that resist erosion) so often the 'stair case/steps/traps, remain long after other geological features have been eroded away.(a basalt compound.--where is stales when i need specific chemical compounds?)
but the rock fractures under pressure (so it can be pulverized, and made into gravel)
(trap was one of the word i contributed to the thread on words from the dutch --i suppose they got it from one of the german language groups, but it took hold here in NY (from the dutch))
