Hur länge sedan var carlsbad caverns bildades?

En webbplats ägnas åt grottans geologi (rozylowicz.com) ger passage starten i redan brutna Permian kalksten, som 20-30MA, efter höjningen hade avancerat tillräckligt för karst utveckling att starta. Jag har också sett någon annanstans en ålder av<4MA, but="" that="" was="" based="" on="" analysis="" of="" minerals="" in="" one="" area="" of="" the="" system.="" i="" would="" though="" treat="" rozy="" lowicz's="" work="" with="" some="" caution="" because="" it="" implies="" the="" cave's="" large="" passages="" and="" chambers="" were="" formed="" by="" collapse,="" not="" dissolution.="" this="" cannot="" happen.="" collapses="" fill="" caves,="" not="" form="" them.="" for="" breakdown="" to="" occur,="" there="" has="" to="" be="" a="" void="" for="" the="" weakened="" rock="" to="" collapse="" into;="" and="" in="" the="" active="" phase="" of="" the="" passage="" the="" stream="" erodes="" fallen="" rock="" away. ="" a="" karst="" cave="" passage="" can="" only="" be="" formed="" by="" a="" stream;="" but="" infilled="" by="" blockfall="" as="" percolation="" water="" attacks="" the="" rock="" surrounding="" the="" joints="" in="" the="" roof="" rock.="" far="" more="" likely="" the="" dry="" passages="" in="" carlsbad="" caverns="" are="" like="" those="" in="" any="" fossil="" cave="" (including="" a="" far="" more="" modest="" cave i="" am="" helping="" explore):="" the="" original="" streams="" have="" changed="" courses="" or="" disappeared="" altogether;="" and="" the="" dry="" passages="" are="" now="">