 The Crater Glacier ( also known as Tulutson Glacier ) is a geologically young glacier that is located on Mount St. Helens , in the U.S. state of Washington . The glacier formed after the 1980 Eruption and due to its location , the body of ice grew rapidly , unknown to the public for nearly 20 years . The glacier once contained ice caves in the smooth ice before the 2004 @-@ 2008 volcanic activity . The growth of the lava dome and volcanic eruptions from 2004 to 2008 significantly altered the appearance of the glacier . In the same time period , several agencies decided to put an official name on the glacier which , at first , was Tulutson Glacier . A later decision made Crater Glacier the official glacier name . Despite the volcanic activity , the glacier continued to advance and by mid @-@ 2008 , the glacier completely encircled the lava domes . In addition , new glaciers ( rock or ice ) have formed around Crater Glacier as well . 
