Crater Glacier: Difference between revisions

True to its name, the glacier lies inside the north-facing [[Volcanic crater|crater]] left by the [[1980 eruption of Mount St. Helens]] and the glacier's elevation is about {{Convert|6794|ft|m|0|abbr=on}}.<ref>{{Cite web|title=Crater Glacier, Washington|url=http://www.topoquest.com/place-detail.php?id=2090268|publisher=[[TopoQuest]]|access-date=2008-07-10}}</ref> A massive central lava dome emplaced from 1980 to 1987 occupies the center of the crater, and the glacier formed in the shape of a [[horseshoe]] around the dome, with two terminal [[moraine]]s on the eastern and western sides. Heavy winter [[snowfall]], repeated snow [[avalanche]]s, [[rockfall]]s, and sun-shading by the surrounding cliffs to the south, led to the exceptionally rapid growth of this glacier.<ref>{{Cite web|title=DESCRIPTION: Mount St. Helens Snowpack and Ice Accumulation|url=http://vulcan.wr.usgs.gov/Volcanoes/MSH/SnowIce/description_msh_snow_ice.html|publisher=[[United States Geological Survey]]|date=2001-05-23|first=Lyn|last=Topinka|access-date=2008-06-08}}</ref> Thus, the glacier composition is estimated to be 60% ice and 40% rock,<ref name="TNT"/> with an average thickness of 328&nbsp;feet (100&nbsp;m)<ref>{{Cite web|title=DESCRIPTION: Mount St. Helens Glaciers and Glaciations|url=http://vulcan.wr.usgs.gov/Volcanoes/MSH/Glaciers/description_msh_glaciers.html|publisher=[[United States Geological Survey]]|first=Lyn|last=Topinka|date=2006-03-01|access-date=2008-06-08}}</ref> and a maximum thickness of around 656&nbsp;feet (200&nbsp;m); nearly as deep as [[Mount Rainier]]'s [[Carbon Glacier]].<ref name="VR"/> None of the [[ice]] is older than the year 1980, but by 2001 the volume of the new glacier was about 40%-50% as large as all the pre–1980 glaciers combined.<ref name=ecologicalResponses>{{Cite book| last1 =Dale | first1 = Virginia H.|last2=Swanson|first2=Frederick J.|last3=Crisafulli|first3= Charles M.| title = Ecological Responses to the 1980 Eruption of Mount St. Helens | publisher = Van Winkle Publishing Co | year = 2005 | page = 34 | isbn = 9780387281506}}</ref> The surface of the glacier looks dark and dirty in the summer due to the numerous rockfalls from the steep, unstable crater walls along with ash from eruptions, all of which help to insulate and protect the growing glacier.<ref name="REBUILD">{{cite web | last = Schilling | first = Steve P. |author2=David W. Ramsey |author3=James A. Messerich |author4=Ren A. Thompson | title = USGS Scientific Investigations Map 2928: Rebuilding Mount St. Helens | url= http://pubs.usgs.gov/sim/2006/2928/ | date = 2006-08-08 | access-date = 2007-03-07 }}</ref><ref name="Brugman81">{{cite web | last = Brugman | first = Melinda M. |author2=Austin Post | title = USGS Circular 850-D: Effects of Volcanism on the Glaciers of Mount St. Helens | url= https://pubs.er.usgs.gov/publication/cir850D | year = 1981 | access-date = 2013-08-31}}</ref><ref name="Wiggins02" >{{cite journal | last = Wiggins | first = Tracy B. |author2=Hansen, Jon D. |author3=Clark, Douglas H. | title = Growth and flow of a new glacier in Mt. St. Helens Crater | journal = Abstracts with Programs - Geological Society of America | volume = 34 | issue = 5 | pages = 91 | year = 2002 }}</ref><ref name="Schilling04">{{cite journal | last = Schilling | first = Steve P. |author2=Paul E. Carrara |author3=Ren A. Thompson |author4=Eugene Y. Iwatsubo | title = Posteruption glacier development within the crater of Mount St. Helens, Washington, USA | journal = Quaternary Research | volume =61 | issue =3 | pages =325–329 | publisher = Elsevier Science (USA) | year = 2004 | doi = 10.1016/j.yqres.2003.11.002 |bibcode = 2004QuRes..61..325S | s2cid = 128528280 }}</ref><ref>{{cite journal | last = McCandless | first = Melanie |author2=Plummer, Mitchell |author3=Clark, Douglas | title = Predictions of the growth and steady-state form of the Mount St. Helens Crater Glacier using a 2-D glacier model | journal = Abstracts with Programs - Geological Society of America | volume = 37 | issue = 7 | pages = 354 | year = 2005 }}</ref> The 2004-2008 volcanic activity created a series of domes that nearly split the glacier into two lobes at the south end of the crater.<ref name="REBUILD"/> In spite of the four-year lava dome building period, the glacier remains [[North America]]'s youngest and fastest growing glacier.<ref name="GROW2"/> With the joining of the termini on the north end of Crater Glacier in May 2008, the body of ice completely encircles the lava domes.<ref name="SE"/><ref name="NT"/> Meltwater from the glacier gives rise to [[Loowit Creek]].<ref>{{cite web|url=http://www.waterfallsnorthwest.com/nws/waterfall.php?st=WA&num=663|title=Loowit Falls|date=2008-01-20|access-date=2008-12-15}}</ref>