Date of Award

Spring 6-14-2026

Document Type

Thesis (Undergraduate)

Department

Earth Sciences

First Advisor

Marisa Palucis

Second Advisor

Meredith Kelly

Abstract

The timing and mechanisms driving the retreat of the Laurentide Ice Sheet (LIS) after the Last Glacial Maximum (LGM; 26-19 ka) in the Presidential Range of the White Mountains, New Hampshire, remains inconsistently interpreted. King Ravine, located within the Presidential Range, contains a landform that preserves geomorphic evidence relevant to this debate. Here, I investigate the origin of this landform by assessing its age, surficial morphology, and internal structure. I present a topographic analysis of King Ravine, including a detailed new geomorphic map of the drainage basin and deposit. To constrain the timing of landform formation and activity, I determined three 10Be surface exposure ages of boulders from the toe of the deposit. I also conducted a lateral Ground Penetrating Radar (GPR) survey to characterize the internal structure of the feature. In addition, I collected five water samples from sites above, below, and outside the deposit to compare isotopic signatures across the drainage area.

The new geomorphic map documents that the feature exhibits ridge-and-furrow topography characteristic of long-term deformation under shear stress, rather than rapid depositional emplacement. The three 10Be surface exposure ages are partially scattered, ranging from 13,080–10,310 yrs. The scattering could be attributed to post-depositional processes, such as erosion, and toppling and settling during movement which can reset or reduce the apparent surface exposure age, possibly explaining the younger samples.

Based on these observations, I interpret the landform to be a relict rock glacier. Herein, I explore several different hypotheses for the mechanism of how this feature may have formed (i.e., a glaciogenic versus permafrost origin). My preferred interpretation is that the King Ravine rock glacier formed from remnant late Wisconsinan ice that persisted in the valley following deglaciation and was subsequently insulated by rockfall derived from post-Laurentide mass wasting along the headwall. Future work would allow further testing of this hypothesis and would provide a better understanding of how rock glaciers develop and interact with changing climatic conditions in alpine environments. Further study of this landform could also provide insight into constraining the mechanism, rate, and timing for the retreat and thinning of the LIS within the Presidential Range. More broadly, the formation of this landform likely records increased post-glacial erosion and landscape instability following LIS retreat from the region following the LGM.

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