1. The fourth sump has been dived for to an underwater boulder choke . 2. In September 2006 cavers squeezed through an excavated boulder choke into new passage. 3. The cave sometimes floods, with a sump forming beyond the first boulder choke . 4. Downstream, the team reached a terminus at a prominent boulder choke , through which they attempted to dig. 5. Boulder chokes can be formed by rockfall, massive earth movement, mining debris, or deposition after storms.6. The underground debris from the collapse forms the Big Rapids and is responsible for the boulder chokes seen near Blank Passage. 7. Originally accessed through a vertical boulder choke , an access tunnel has been cut to include it on the visitor trail. 8. The stream runs through the cave until it comes to a boulder choke which has so far proved to be impenetrable. 9. Boulder chokes can present a significant danger to cavers, as unstable boulders can unexpectedly move, potentially crushing or trapping cavers.10. Passing a little further through a few boulder chokes brings you through many wonderfully decorated chambers and eventually to the Hall of 30.
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