Assessing the style of advance and retreat of the Des Moines Lobe using LiDAR topographic data

dc.contributor.advisor Neal R. Iverson Day, Sarah
dc.contributor.department Geological and Atmospheric Sciences 2018-08-11T14:18:06.000 2020-06-30T02:51:13Z 2020-06-30T02:51:13Z Wed Jan 01 00:00:00 UTC 2014 2001-01-01 2014-01-01
dc.description.abstract <p>Successive advances of the late-Wisconsinan Des Moines Lobe to form three major end moraines in Iowa--sequentially the Bemis, Altamont, and Algona moraines--are thought to be the result of the lobe surging out of balance with a warming climate. Various styles of hummocky topography, collectively sometimes called stagnation moraine, are interpreted to be the result of widespread stagnation and down-wasting of ice following surges. Alternatively, end moraines could be recessional--a result of incremental back-wasting of the glacier margin and unrelated to surging.</p> <p>To study the retreat style of the Des Moines Lobe, high resolution LiDAR data were used to re-evaluate the subtle landscape of the lobe's footprint in Iowa. Results indicate that ~90% of the lobe's area, excluding major Holocene stream drainages, consists of stagnation features. Some landforms are more prevalent than mapped previously, including eskers and features interpreted to be subdued ice-walled lake plains. Importantly, subglacially formed minor moraines (a.k.a. washboard moraines), which resulted from sediment filling of transverse crevasses, cover ~60% of the lobe's area with stagnation landforms. Also, ~25 previously unmapped end moraine ridges have been identified.</p> <p>Transverse crevasse-fill ridges in the forefields of modern glaciers form due to longitudinal ice extension associated with surging and are not found in the forefields of non-surge-type glaciers, so minor moraines are good evidence of Des Moines Lobe surges. Most end moraines have minor moraine sets associated with them, consistent with a surge-like advances, and many areas have multiple sets of minor moraines indicating a surge history more complicated than one advance for each of the three major end moraines. Therefore, asserting stagnation and down-wasting after three surge-like advances provides an incomplete characterization of the Des Moines Lobe's advance and retreat. The surge-type Bering Glacier in Alaska is a good but imperfect modern analog for the lobe.</p>
dc.format.mimetype application/pdf
dc.identifier archive/
dc.identifier.articleid 4660
dc.identifier.contextkey 5777340
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/13653
dc.language.iso en
dc.source.bitstream archive/|||Fri Jan 14 19:57:51 UTC 2022
dc.subject.disciplines Geology
dc.subject.disciplines Geomorphology
dc.subject.keywords Des Moines Lobe
dc.subject.keywords End Moraine
dc.subject.keywords Glacier
dc.subject.keywords Minor Moraines
dc.title Assessing the style of advance and retreat of the Des Moines Lobe using LiDAR topographic data
dc.type article
dc.type.genre thesis
dspace.entity.type Publication
relation.isOrgUnitOfPublication 29272786-4c4a-4d63-98d6-e7b6d6730c45 thesis Master of Science
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