Dating the Cheops Glacier with Lichenometry, Dendrochronology and Air Photo Analyses
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Dating the Cheops Glacier with Lichenometry, Dendrochronology and Air Photo Analyses By: Janek Wosnewski, Sean Hillis, Dan Gregory and Kodie Dewar December 09, 2009 Geography 477 Field School Instructor: Dr. James Gardner 1 Table of Contents 1.0 Introduction ..…………………………………………………………... 3 1.1 Background Information …………………………………………3 1.10 Cirque Glacier ………..…….………..….……….……….5 1.11 Dendrochronology …..…………………………....……...6 1.12 Lichenometry ……….……….…………………………...7 2.0 Site Description …..……………………………………………….….…9 2.1 Description ……………...………………………………….….…9 2.2 Climate …………………………………………………….…..…9 3.0 Dendrochronology …………………………………………………..…12 3.1 Methods ……………………………………………………....…12 3.2 Results ……………………………………………………......…14 3.3 Sources of Error…………………………………………....……15 4.0 Lichenometry …………………………………………………….....…16 4.1 Methods ……………………………………………………...…16 4.2 Results ……………………………………………………..……17 4.3 Sources of Error……………………………………………....…19 5.0 Discrepancies in Lichenometry and Dendrochronogoly Data ……...…21 6.0 Air Photo Analysis…………………………………………………..…22 6.1 Results …………………………………………………..………27 6.2 Sources of Error ………………………………………...………28 7.0 Discussion and Conclusion…………………………………….....……29 8.0 References………………………………………………….………......31 2 1.0 Introduction 1.1 Background Information Glacier National Park which was established in 1886 is situated in the Columbia Mountain regions of British Columbia and hosts a wide variety of plants, animals and ecosystems (Parks Canada, 2009). The park protects a wide variety of plant and animal life and has a specific management plan for each of the others that are of concern. The history in the park, particularly in the Rogers Pass area is very unique. Rogers pass is home to a national historic site known as Glacier House which was a luxurious hotel that hosted the many travelers brought in on the Canadian Pacific Railway and was a pioneer in the mountain hotel business. The Columbia Mountains are extremely rugged with steep terrain and are subjected to harsh climate conditions. The geomorphology is unlimited with the combination of steep terrain and large annual precipitation. There are numerous alpine glaciers and fluvial systems throughout the park that are constantly eroding the ever changing landscape. Glacier National Park is ~135 000 hectares and has an elevation at Rogers pass of 1382m with many mountains in the region reaching heights of 2500 metres. The park is situated in the Columbia Mountain range east of Revelstoke BC, specifically in the Selkirk and Purcell ranges. In the Rogers Pass area there are permanent buildings such as a Ski lodge and a Parks Canada Maintenance yard. In the summer months the area is full of avid hikers and when the winter hits adventurous ski touring groups take over. The TransCanada Highway runs through the park and the largest avalanche control program in the world is operated by Parks Canada in this very pass. 3 The parks goals are to protect the plants and animals in the region and preserve the natural beauty of the area. The dominant tree species in the region consist of old growth Cedar and Mountain Hemlock stands. The major big game animals that are being monitored are grizzly bears, mountain caribous and mountain goats. Throughout the park there are numerous trails that lead into the alpine, many of which have been there since the park was establish and were built by Swiss guides that were brought to the area. Glacier National Park was the first park in BC and has a very unique history to it. Within the park is Rogers Pass which is named after Major A.B. Rogers, who found the route after a long and treacherous journey for the Canadian Pacific Railway in 1885 (Parks Canada, 2009). The new railroad brought many adventurous travels west to seek to lives and to experience the Rocky Mountains. The Rogers Pass area was starting to become a very luxurious place to visit because of the wonderful scenic views in the summer and also the wonderful ski touring in the winter. Glacier House was the first hotel in the region and quickly grew to accommodate the massive influx of travels. Glacier House, now dismantled, is part of a national historic site in the Rogers Pass area and is viewed as the inspiration of similar buildings and services such as Banff Springs, Hotel Vancouver and Chateau Lake Louise (Parks Canada, 2009). The steep terrain and high precipitation give rise to some of the most interesting geomorphology in the world. Glaciers once covered the majority of Canada and now they cover less than 10% (Parks Canada, 2009). In Glacier National Park there are many alpine glaciers including the Illecillewaet formally known as the Great Glacier, the Asulkan, and the 4 focus of this project, the Cheops glacier. The formations left behind by these glaciers show a history and if studied properly can tell a story of how these formations were formed. Figure 1 - Glacier National Park of Canada (Parks Canada, 2009). 1.10 Cirque Glacier Glaciers are defined as a body of moving ice that has been formed on land by compaction and recrystallization of snow (Ritter et al, 2002). There are two major requirements that must be met before an ice mass can be considered a glacier; these being the formation of the ice mass must be from the accumulation and metamorphism of snow as well as the ice must be moving internally or as a sliding block (Ritter et al, 2002). Throughout the 5 literature glaciers have been classified based on a number of morphological, dynamic and thermal properties including size and growth environment (Ritter et al, 2002); however Flint (1971) suggests that glaciers can be put into three broad categories that include cirque glaciers, valley glaciers and ice sheets. Cirque glaciers, like the one that is present in our study area, are defined as: Flowing ice streams restricted to amphitheatre-shaped depressions in valley headlands (Ritter et al, 2002). 1.11 Dendrochronology Dendrochronology is defined as the science that deals with the dating and study of annual growth layers in trees or shrubs, commonly referred to as tree rings (Smith and Lewis, 2007a). Tree rings form as a result of cambium cells being active during the spring when the xylem cells produced are large and thin-walled, and dormant during the winter when xylem cells are smaller and thick-walled (Smith and Lewis, 2007a). Xylem cells that form in the active growing season are commonly known as spring or earlywood, where cells that form in the dormant months are known as summer or latewood; it is this distinct difference between early and latewood cells that allows for the identification of annual growth rings (Smith and Lewis, 2007a). Dendrochronology as a scientific discipline has many different applications and branches which date as far back as the 15th century when Leonardo da Vinci observed the annual nature of tree-rings through the relationship between their widths and precipitation (Smith and Lewis, 2007a). Of the several branches that make up dendrochronology including dendroglaciology, dendroclimatology and dendrogeomorphology; 6 dendroglaciology is the branch that most caters to this report due to its use of tree rings to date the movement of glaciers as well as the age of moraines and other glacial deposits (Smith and Lewis, 2007b). The dating of glacial moraines is a multi step process that involves counting the number of rings at the base of the moraines oldest tree to determine its minimum age (Koch, 2009). Next a value that take into account the lag period between glacial retreat or moraine formation and tree germination is added to the age of the oldest tree to give the true age of the moraine (Smith and Lewis, 2007b; Mcarthy and Luckman, 1993). This lag period, known as the ecesis rate, is a site specific value because germination times can be greatly affected by differing geology, topography and microclimate (Koch, 2009). The ecesis rate for an area can be obtained through a number of techniques including taking tree-ring or seedling samples from an area of know age or using air photos of the area to estimate the rate of glacial retreat (Mcarthy and Luckman, 1993). 1.12 Lichenometry Spatial analysis of moraines can be difficult to achieve because they are often subject to significant modification during subsequent phases of glacial advance and retreat. Interpretation of past glacial activity becomes complicated due to variable ice margin activity over time. For example: individual moraines can be unique and reveal evidence of bifurcation and cross cutting patterns from differential ice retreat (Bennet, 2001). Prominent glacial depositional features such as terminus, lateral, and medial moraines are deposited during phases of glacial retreat. These 7 features are often deposited in a uniform manner which suggests a steady rate of glacial recession. This means that the depositional material forming the moraine will be of similar age and subject to similar post-depositional environmental, geomorphic, and glacial modification, thus suggesting that these surfaces will have similar history. The identification of these surfaces may provide a useful method to identify the location or extent of former ice margins (Dugmore et al, 2008). Once these surfaces are exposed, they are susceptible to invasion from plant colonization (McCarthy & Luckman, 1993). The fastest known colonizing species on a substrate surface is lichen. The colonization and growth of lichen allows for study and analysis of the surface on which it is found. More specifically, the analysis of its growth is referred to as lichenometry and is a technique that has been used extensively for the dating of geomorphic features in the past (Lindsay, 1973). Lichenometry is a calibrated-age dating technique used to establish a minimum surface date of rocks using measurements of lichen thallus diameter (Allen & Smith, 2007). The lichen diameter is measured and correlated to the age of the surface it is found on, whether it is wood, dirt, or substrate. It is a technique that was first introduced in the early 1930's but was later developed by Roland Bechel who brought it to the forefront of the scientific community (Lindsay, 1973; Webber & Andrews, 1977).