 With the volcanic activity from 2004 to 2008 , the glacier lobes were pushed aside and overthickened by the growth of new volcanic domes . As the two streams of ice were compressed between the caldera wall and the new lava domes , the ice moved rapidly downhill , much like the squeezing of toothpaste out of a container . This resulted in a very rapid advance of the glacier termini ; first the western glacier arm merged with the rock glacier on the western crater wall and then , both arms of the Crater Glacier joined north 1980s lava dome in May 2008 , despite the volcanic activity . In addition , the volcanic activity modified the surface of the glacier and transformed it from being mostly crevasse @-@ free to being a chaotic jumble of icefalls heavily criss @-@ crossed with crevasses and seracs due to movement of the crater floor and lava dome growth . At the south end , the new domes almost split the Crater Glacier into two separate glaciers and melted 10 % in volume of the glacier 's ice . However , cold rock on the edge of the glacier insulated the glacier ice from the 1 @,@ 300 ° F ( 700 ° C ) lava spewing out of the lava domes , easing concerns of a catastrophic lahar caused by glacier melting . The porous nature of the crater floor also reduced the amount of meltwater flowing out of the caldera . 
