Dating the Cheops Glacier with Lichenometry, Dendrochronology and Air Photo Analyses

Transcription

1 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

2 Table of Contents 1.0 Introduction Background Information Cirque Glacier Dendrochronology Lichenometry Site Description Description Climate Dendrochronology Methods Results Sources of Error Lichenometry Methods Results Sources of Error Discrepancies in Lichenometry and Dendrochronogoly Data Air Photo Analysis Results Sources of Error Discussion and Conclusion References

3 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 ~ 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

4 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

5 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) 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

6 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) 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 15 th 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

7 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) 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

8 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). Lichenometry uses the assumption that a lichen thallus diameter is proportional to the lifespan or time that a lichen has grown on a surface, and in turn is proportional to the age of the surface on which it is found. 8

9 In this study we use the lichenometry dating technique to determine the age of the depositional moraines found within the Mount Cheops glacier region. This technique, in combination with dendrochronology and air photo analysis, is ultimately used to determine the different historical ice margins of the Mount Cheops glacier. 2.0 Site Description 2.1 Cheops site The Cheops glacier is located in the cirque on Cheops Mountain and is reached from the Balu Pass trail. To reach the glacier you must travel up the trail ~2km then venture South off the path and up a creek bed to the site. Cheops Mountain is at ~2650m elevation and has moderate to extremely steep terrain. The cirque faces north which means it is sheltered from the sun and it is this very attribute that has prolonged the life of the Cheops glacier. An interesting situation occurred when Parks Canada was questioned about the Cheops glacier and they responded by saying that there was no glacier in the Cheops cirque. This goes to show how much of a hidden gem the Cheops glacier really is. 2.2 Climate Climate plays one of the largest roles when it comes to the advancement and retreat of a glacier. The Glacier National Park region is subjected to winters with high snowfall and moderate temperatures (Parks Canada, 2009). Lots of the weather forecasts in the area tend to be unreliable because of the variations in topography which create large barriers between adjacent valleys (Parks Canada, 2009). 9

10 The Little Ice Age was a period of cooling and an era of advancement for glaciers. Depending on the location it occurred anywhere from ~900 to ~650 years ago and is believed to have been the time when the alpine glaciers in the Revelstoke area reached their farthest extent. As quoted by Koch et al (2007), The glaciers reached their furthest extents between This extent is marked by the terminal moraine and on the Cheops glacier sufficient evidence was gathered in order to produce an age of when the glacier reached its maximum. Climate change in the Glacier National Park area consists of warming temperatures and decreasing precipitation amounts. In figures 2.21 and 2.22 it can be seen that these events are happening at an alarming rate. Since the 1960 s the mean annual temperature has increased approximately by 1.5 o C and the mean annual snow fall has decreased by approximately 25cm. With the combination of; increasing temperatures creating increased melt, and decreasing snow fall creating less accumulation, it can be hypothesized that the future does not look good for glaciers in the Glacier National Park area. 10

11 Figure 2.1- Mean Temperature in Rogers Pass, B.C. since Figure Mean Snowfall in Rogers Pass, B.C. since

12 3.0 Dendrochronology 3.1 Methods For the purpose of estimating the approximate age of the larger, more heavily vegetated right lateral and medial moraines, tree core samples were extracted with a 5mm increment borer from a number of trees found growing on the surface of these moraines. In accordance to the principal of replication two cores were sampled from multiple trees as close to the base of the tree as possible (Smith and Lewis, 2007a). This principal states that by taking multiple samples from the base of several trees in the same area, intra-tree variability as well as the influence of undesired environmental factors, and missing or false rings will be reduced when dating the glacial feature (Smith and Lewis, 2007a). In total 10 cores were collected from the east lateral moraine and 14 cores were collected from the medial moraine. When trees were deemed too small to be cored their whorls were counted assuming that each whorl represented a year of growth. This procedure was applied to trees growing on two glacial scars in order to date the time of their formation. In addition branch samples were taken of the trees for the purpose of species identification. All trees growing on the east lateral and medial moraines were identified to be Sub-Alpine Fir. Approximately fifteen tree core samples were extracted from a number of large trees (identified to be Hemlock) growing west of the medial moraine. This was done for the purpose of estimating the maximum extent of the glacier in our study area. According to Koch et al. (2007) glaciers in the Coast Mountains reached their maximum extent in the Little Ice Age between the dates of A.D and Unfortunately the majority of the oldest trees in this area were rotten and only 4 of the extracted cores were able to be analyzed and dated. The annual growth layers of these 4 tree core 12

13 samples were counted and after an ecesis rate (calculated for Hemlock trees on the Illecillewaet glacier) was applied, the formation the substrate in this area was dated back to 1643 (See Table 3.1). This date precedes the period of glacial maximum extent suggested by Koch et al. (2007) and establishes that the glacier never reached this point of our study area. After the required samples had been taken tree core and branch samples were transported to the University of Victoria Tree Ring Lab for analysis. Tree core samples were glued onto wooden blocks and sanded multiple times in order to make the individual rings more distinguishable and easier to count. The use of a microscope aided in the counting of individual rings which were recorded using the program WinDendro. Ring counts were than analyzed to determine the oldest tree on each of the moraines for the purpose of applying an ecesis rate to determine the actual age of the moraines. The determination of an ecesis rate unique to our study area proved to be a difficult task due to a lack of areas of known age within our region, or aerial photographs showing maximum glacial extent. If these pieces of information had been available they could have been utilized to calculate an ecesis rate specific to our study site. This lack of prior data forced the use of previously determined ecesis rates calculated for the Asulkan and Illecillewaet glaciers by McCarthy and Luckman in 1993 and These ecesis rates are not ideal but were considered to be valid for determining the age of the moraines in our study area because they have been calculated for Sub-Alpine Fir and Hemlock trees (the same species of tree we collected cores from) and because the Illecillewaet and Asulkan glaciers are located in a microclimate similar to our study area. These ecesis rates, determined to be 45 years for the Asulkan glacier and 35 years for the Illecillewaet glacier 13

14 (Mcarthy and Luckman, 1993 and Mcarthy 2003), were added to the age of the oldest tree found on the right lateral and medial moraines to give an estimate of their age (see Table 3.2 and Table 3.3). An ecesis rate of 40 years was applied to the Hemlock trees growing west of the medial moraine in accordance to the Illecillewaet ecesis rate calculated for Hemlock trees. 3.2 Results Table 3.1- Date and age of area west of medial moraine Tree Species: Hemlock Ecesis Rate: (40 yrs Illecillewaet) Germination Date of Oldest Tree Age (yrs) of Oldest Tree Age of Substrate With Illecillewaet Ecesis Rate Date of Area Table 3.2-Date and Age of East Lateral Moraine Tree Species: Sub-Alpine Fir Ecesis Rate: (35 yrs Illecillewaet) (45 yrs Asulkan) Age (yrs) of Oldest Tree Age With Illecillewaet Ecesis Age With Asulkan Ecesis Date of Moraine With Illecillewaet Ecesis Date of Moraine With Asulkan Ecesis Germination Date of Oldest Tree 14

15 Table 3.3-Date and Age of Medial Moraine Tree Species: Sub-Alpine Fir Ecesis Rates: (35 yrs Illecillewaet) (45 yrs Asulkan) Germination Date of Oldest Tree Age (yrs) of Oldest Tree Age With Illecillewaet Ecesis Age With Asulkan Ecesis Date of Moraine With Illecillewaet Ecesis Date of Moraine With Asulkan Ecesis Sources of Error Possible sources of error in this project include the use of ecesis rates not specific to our study site, false or missing tree rings, missing the pith when tree core samples were extracted and failure to locate the oldest tree on the feature being dated. The utilization of ecesis rates calculated for the Asulkan and Illecillewaet glaciers may have resulted in the dates of the moraines in our study area being over or under estimated. While these glaciers are in close proximity to our study area slight differences in microclimate, topography, geology and elevation could cause the germination rates in these areas to be different from our study area (Koch, 2009). The presence of false rings in our tree core samples could have caused over estimation of moraine age while under estimation could have been the result of missing rings or failure to locate the oldest tree on the moraine (Koch, 2009). Failure to reach the pith of the tree in our tree core samples was not a direct source of error for our project as all our sampled cores included the pith, however if the pith had been missed reliance on the estimation of missing rings could have caused ages to be over or under estimated (Koch, 2009). 15

16 4.0 Lichenometry 4.1 Methods Lichen sampling for the Mount Cheops glacier study site was conducted on the most prominent glacial features in the area. These features consisted of 3 major moraines; two lateral moraines on the eastern side of the site and one medial moraine on the western portion. There was a large moraine that was formed into the mountain side on the most western side of the Mount Cheops glacial site but was not sampled due to its extremely steep topography and dangerous climbing conditions. Lichens were sampled from the entire top ridge of each moraine, while careful measures were taken to avoid sampling on the proximal and distal sides. For each moraine a total of 30 lichen samples were collected. Each moraine was broken into 6 sample areas, from which 5 samples were taken at each site. The sample sites were evenly distributed over the entire span of the moraine to allow an adequate representation of lichen cover for each. 10 lichen samples were also collected from the remnants of a small moraine located directly below the western medial moraine on the eastern side. Because only 10 samples were collected, the validity of dating this feature may not be adequate. This moraine looked like it lined up with the lower eastern lateral moraine so dating this feature was attempted; however it was not the main focus of study. The lichen species of focus were healthy yellow/green Rhisocarpon geograhicum, which are renowned for their long life spans and slow growth rates (Benedict, 1988). Only the maximum diameter of the largest lichen thallus was sampled because it is assumed that maximum thallus diameter 16

17 possess the optimum growth rate and is indicative of the oldest substrate age (Calkin and Ellis, 1980). Also, only the circular or ellipsoidal lichens were considered for measurement. These sample restrictions were applied while sampling thalli on each moraine and therefore allowed for consistency suitable for comparison between each feature. The lichen thalli measurements were taken with a digital caliper and were measured with an accuracy of +/- 1 mm. Each thallus sample involved two measurements; one at the horizontal x-axis of the thallus, and one directly perpendicular to the first, at the y-axis. These values were recorded and stored for further analysis. Calculations of the samples included the determining the mean of the x-axis and y-axis thalli measurements for each sample. This was done to decrease the chances of over or underestimating the substrate age based on the measurements. The mean of each moraine was then calculated to give an overall representative lichen thallus size for each feature. The mean lichen thallus for each moraine was then applied to the McCarthy Growth curve of the Illicilewaet glacier (McCarthy, 2003). 4.2 Results The mean Rhizocarpon geographicum lichen diameter was calculated for each land form and applied to the McCarthy Growth Curve as shown in figure 4.1. The lichen thalli diameters applied to the growth curve are the best representation of each individual moraine's overall thallus size. The respective thalli diameters are as follows. The lower eastern lateral moraine mean thallus diameter was mm, which produces a substrate age of

18 years. Next was the upper eastern lateral moraine, giving a mean thallus diameter of mm which produces a substrate age of 170 years. The western medial moraine had a mean thallus diameter of mm, which generates a substrate age of 201 years. Lower Eastern Lateral Moraine x = 33.34mm y = 110 years old Upper Eastern Lateral Moraine x = 53.70mm y = 170 years old Western Medial Moraine x = 59.56mm y = 201 years old Figure Lichen Growth Curve for the Illecillewaet Glacier (McCarthy, 2003) The remnants of the small moraine located directly below the western medial moraine on the eastern side provided a mere 10 lichen samples. This was due to the proportion of the feature's size compared to the other moraines studied. With only ten samples, the credibility of lichenometric dating on this feature may be invalid. However, the mean thallus diameter was mm and when applied to the McCarthy growth curve, provides a substrate age of 123 years. The respective ages of the moraines are shown in table

19 Table Mean thallus size, age, and depositional year for each moraine Lower Eastern Lateral Moraine Upper Eastern Lateral Moraine Western Lateral Moraine Lower Western Moraine Remnants Thallus Diameter Age Respective Year mm 110 years mm 170 years mm 201 years mm 123 years Sources of Error It is important to look at factors that may influence lichen growth because favorable conditions may skew substrate dating results. Lichenometry in the past has been criticized for its absence of recognition of ecological factors that influence the growth rates of lichens. However, it is now assumed that both streams and snow cover have an effect on the growth rates of Rhizocarpon lichens (Innes, 1985). Studies from the past indicate that moisture availability and proximity to streams or lakes promote growth in rhizocarpon thalli. Snow cover on the other hand tends to restrict lichen growth and limit the surface availability that lichen grow on. Also, close proximity to snow cover often results in smaller lichen thalli than usually expected (Innes 1985). These factors may influence our findings because both of the eastern lateral moraines were close to glacial ice and water. There was no snow cover on any of the substrate however; the eastern tongue of the Mount Cheops glacier ran parallel to the upper portion of the eastern lateral 19

20 moraine. According to Innes (1985), the proximity of this ice may have inhibited the growth rate and influenced the size of our sampled thalli. The lower portion of the secondary eastern lateral moraine is also susceptible to this information because the glacial melt water formed the headwall of a stream which ran parallel to this feature. According to Innes (1985), this proximity to moisture may have increased the growth rate of the sampled lichen on the lower portion of the lower eastern moraine and may have influenced our results. Luckman (1977) outlines two important variables that also may contribute to dating errors when using lichenometry. Firstly he raises the issue similar to that Innes (1985) in regards to lichen growth rate variability on both a regional and local scale. The lichen growth rate variability can be influenced by factors such as moisture availability, temperature, duration of snow cover, and the composition of the host substrate itself. Secondly, he mentions that the use of the largest lichen thalli as indicators of substrate age may contribute to error. Larger lichen may be found on older substrate debris and favorable local environmental conditions may also result in abnormally large lichen growth rates. A significant factor that may increase error in our lichenometry dating is the fact that we did not use a lichen growth curve constructed specifically for our glacier. We instead used McCarthy s Illecillewaet lichen growth curve which was designed specifically for the Illecillewaet glacier. This growth curve was chosen because the Illecillewaet glacier is located in the same general region, has a comparable elevation, and similar micro climate to the Mount Cheops glacier. Although these factors may produce a similar 20

21 lichen growth rates between the two sites, Mount Cheops may be different and using a non specific growth curve may skew results. It is also important to note that an ecesis value was not used in our lichenometry technique. An ecesis rate refers to the time interval between the exposure of a substrate and the colonization of a species such as lichen (McCarthy, 2003). Although it is an important aspect of lichenometry, it was not incorporated in the lichenometric dating of Mount Cheops moraines. This because the McCarthy growth curve was used to determine our substrate dates. The McCarthy growth curve directly relates the lichen thalli diameters to the age of the surface they are found on. It is in this relationship that we assume the ecesis value is incorporated. Thus an ecesis value was not added to the age produced when correlating our lichen thalli diameters to the growth curve. 5.0 Discrepancies in Lichenometry and Dendrochronogoly Data The discrepancies in dates between lichenometry and dendrochronogoly data can be explained by the frequent high magnitude avalanches that are seen throughout this area (Parks Canada, 2009). The impacts of avalanches on the slopes of the site would limit the seeding establishment in the pathways of avalanches (S.J. Walsh, 1994). On the other hand, lichen establishment is quick and can occur over the course of one summer. Therefore, discrepancies in dates are within reason and are reasonable when including sources of error. 21

22 6.0 Air Photo Analysis Air photo analysis proved to be a very useful tool is assessing the Cheops glacier. With only a ground level view of the glacier, the aspect of the air photos allow for a clear image of the site. Figure 6.1 Estimated recessional lines A, D, L represent Air photo analysis dates, Dendrochronogoly data dates, and Lichenometry data dates respectively. Air photos were gathered from the Air Photo Warehouse at the Interurban Camosun College campus in Sannich, B.C. dating back to 1951, 1986 and Prior to gathering air photos of the site, location of the terminus was under scrutiny among group members due to the orientation of the site, fluvial deformations, debris cover, and vegetation cover. Air photos from 1951 clearly revealed the location of the glacial terminus through the lack of vegetation cover and deformation (Fig. 6.1). 22

23 Figure 6.2 Air photos taken in 1986 Air photos taken in 1986 provided the clearest image of the site (Fig. 6.2). It was speculated that two separate accumulation zones located at nearest to the head wall lead to the formation a the distinct western medial moraine. Furthermore, since 1951, there has been extensive deformation to the terminal area due to glacial outwash. It can be also noted that large scale deformations occurred to the area above the red line in Figure 6.1. The development of thermokarst type topography could be seen through the debris that remained on the glacier in this same area in air photos from In comparison to the air photo taken in 1951, the relationship of the terminal moraine to the eastern most lateral and western medial moraines 23

24 found at higher elevations was established. Thus, was dated through dendrochronogoly to and 1808 through lichenometry (Fig. 6.3). Scars found on the proximal side of the lower west medial moraine and their corresponding recessional moraines seen in Figure 6.2 laid the path of the date lines drawn in Figure 6.3. Figure 6.3 Estimated recessional lines A, D, L represent Air photo analysis dates, Dendrochronogoly data dates, and Lichenometry data dates respectively. 24

25 Due to the lack of time and man power, data collected to the areas west of the medial moraine was limited. However, tree ring data retrieved from a Mountain Hemlock species in this area lead to the estimated path and extent of the glacier west of the medial moraine (Fig 6.4). This group of Figure 6.4 Orange line represents the farthest most extent of the Cheops Glacier on either side of the medial moraine. Star and Diamond represents tree ring dates of Mountain Hemlocks with an implied 40 year ecesis value 25

26 trees was situated away from the main avalanche corridor such that seedling establishment would not be impacted. Underlying substrates of Mountain Hemlock trees cored and dated to 326 years and 168 years, with an implied an ecesis value of 40 years, dated to 1643 A.D and 1801 A.D. respectively. The trees dated to 1801 A.D. matched up nicely with the lichenometry dates of the terminal moraine. However, trees dates back to 1643 A.D. provided some confusion as why how this tree may be related to the Cheops Glacier. In fact, during the Little Ice Age, glaciers achieved their greatest extent between A.D and 1720 (Koch, 2007) which would lead one to believe that the Cheops Glacier itself achieved its greatest extent around these same dates. This lead to the conclusion that the Cheops Glacier, during the Little Ice Age, did not reach the extent of the tree dated to 1643A.D. and thus the corresponding date lines in Figure 6.4 were established. Air Photos proved to be very useful for the locating lateral, medial, terminal, and recessional moraines that were otherwise tough to pick out on the ground. When relating data from what was found through dendrochronogoly and lichenometry with the air photo analysis, the understanding of the geomorphology processes that took place at this site, along with their corresponding dates in which then occurred, are evident. 26

27 Figure 6.5 Estimated recessional lines A, D, L represent Air photo analysis dates, Dendrochronogoly data dates, and Lichenometry data dates respectively. 6.1 Results Through basic air photo interpretation, retreat rates were established to the air photo taken in 1991 (Fig 6.5). Its scale was calculated through relationships to topographic maps and was determined to be 1: From 27

28 this retreat rates were calculated and classified into different time periods (Table 6.1). Table 6.1 Retreat rates according to time periods Time Period (A.D.) Retreat Rates (m/year) Sources of Error The methods used in calculating the scale of air photos entailed the use of topographical maps that had scales much smaller than those of the air photos used. Consequently, the smaller scales of the topographical maps may have been rounded and not accurate. Air photo interpretation and the above results were calculated used standard rulers for measurements. Subsequently, human error would be large contribution in the error in the results section of the air photo analysis. Throughout the calculation process, measurement on air photos had an accuracy of 1mm and a higher level of accuracy may have bettered the results. The location of green and yellow recessional lines located in Fig. 6 above were estimated and may not have been the precise locations of ice at their given dates. Had the air photos been taken in color or false-color, it may have been easier to locate the extent of the ice at the time the air photos were taken because boundaries of ice and debris would be more distinct. 28

29 Moreover, there debris on the surface of the glacier may have covered ice and masked the true glacial extents at the time the photos were taken. 7.0 Discussion and Conclusion Lichenometry and Dendrochronology were quantitative procedures used in order to find specific dates of moraines left by the Cheops cirque glacier. Air photo analysis was a qualitative process that was also used to date the moraines. Through the use of the first two methods in the field and the third method in the labs, the dates of the moraines were found and a history of the glacier was created. It is very evident all around the Glacier national park area that glaciers are retreating at a substantial rate. This is a direct result of changing climate which was pointed out in figures 2.21 and It is very easy to see the retreat if you have access to Air Photos of the area. The Air Photos collected for this study proved to be extremely useful. They showed significant retreat and from these photos retreat rates were estimated. The estimated retreat rates increased as time went on and are currently greater than 5.6m/yr. It was determined that the Cheops cirque glacier was actually two glaciers which was concluded by the medial moraine seen in the field and in the air photos. The extent of these glaciers was extremely different because of the topography in the area. The Eastern most glacier reached an extent that can be seen by a terminal moraine (Figure 6.5). The Western most terminated over a very steep cliff face and therefore did not have a terminal moraine. 29

30 The results that were found through the use of the three processes correlated very nicely to other studies. It was found that the Cheops glacier reached its extent in an era known as the Little Ice Age. The late advances in the Little Ice Age occurred around the late 1600 s to early 1700 s which correlates to the dates of the moraines that were interpreted through the three study methods (Koch et al, 2007). 30

31 8.0 References: Allen, S.M. and Smith, D.J. (2007). Late Holocene glacial activity of Bridge Glacier, British Columbia Coast Mountains, Canadian Journal of Earth Science, 44: Benedict, J. B. (1988). Techniques in Lichenometry: Identifying the Yellow Rhizocarpons, Arctic and Alpine Research, 20 (3): Calkin, P.E. and Ellis, J.M. (1980). A Lichenometric Dating Curve and its Application to Holocene Glacier Studies in the Central Brooks Range, Alaska, Arctic and Alpine Research, 12(3): Dugmore, A. J., McKinzey, K. M., Orwin, J. F., Stephens, M. A.( 2008). Identifying Moraine Surfaces with Similar Histories Using Lichen Size Distributions and The U2 Statistic, Southeast Iceland, Geografiska Annaler Series A: Physical Geography, 90 (2): Innes, J. L. (1985). Moisture Availability and Lichen Growth: The Effects of Snow Cover and Streams on Lichenometric Measurements, Arctic and Alpine Research, 17(4): Lindsay, D.C. (1973). Estimates of Lichen Growth Rates in the Maritime Antarctic, Arctic and Alpine Research, 5(4): Koch, J. Clague, J.J., Osborn, G.D. (2007). Glacier fluctuations during the past millennium in Garibaldi Provincial Park, southern Coast Mountains, British Columbia, Canadian Journal of Earth Science, 44: Koch, J. (2009). Improving Age Estimates for Late Holocene Glacial Landforms Using Dendrochronology-Some Examples from Garibaldi Provincial Park, British Columbia, Quaternary Geochronology, 4: Luckman, B. H. (1977). Lichenometric dating of Holocene moraines at Mount Edith Cavell, Jasper, Alberta, Canadian Journal of Earth Science, 14:

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