Glacier Maps of the Sierra Nevada de Mérida, Venezuela

Transcription

1 Glacier Maps of the Sierra Nevada de Mérida, Venezuela Source Description Map 1 Jahn (1925) Map showing glacier cover, glacier names, summit names, and summit elevations in the Sierra Nevada de Mérida in 1910/1911. Map 2 Blumenthal (1923) Simple sketch map of the Sierra Nevada de Mérida intended as a guide for hiking and mountain climbing. Map 3 Gunther (1940, 1941a) Gunther s map of the Sierra Nevada de Mérida is based on Jahn (1925) and Gunther s own observations in 1939 and Map 4 Gunther (1940) Highly-generalized sketch map of the glaciers in the Pico Bolivar Massif, useful as an orientation map for climbers. Map 5 Busk (1964) Simple sketch map of the Sierra Nevada de Mérida intended as a guide for hiking, climbing, and trout fishing. Map 6 Schubert (1972) Detailed glacial-geomorphic and topographic map of the Pico Bolivar Massif (Schubert, 1972, Fig. 1). Map 7 Schubert (1972) Simple sketch map comparing glacier extent in 1910/1911 and 1972 in the Pico Bolivar Massif (Schubert, 1972, Fig. 5). Map 8 Schubert (1992) Map comparing glacier extent in the Sierra Nevada de Mérida in 1910/1911 and 1952 as determined from aerial photographs. Map 9, 10 Schubert (1998) Schubert s 1998 maps are generalizations of his 1992 map based on aerial photographs from Map 11 Mahaney et al. (2000) Generalized sketch map based on the available national park hiking map for the Sierra Nevada de Mérida. Map 12 Mahaney et al. (2009) Annotated 1952 aerial photograph map of the Pico Humboldt/Pico Bonpland Massif. Map 13 Mahaney et al. (2009) Sketch map of the Pico Humboldt foreland. The glacier margin was presumably estimated from the 1952 aerial photographs. Map 14 National Park Map (1:50,000) Map of the Sierra Nevada de Mérida and surrounding area showing hiking trails and generalized topography. Map 15 Topographic Map NC Official topographic map NC Merida (1:250,000, contour interval 40 m) produced in Map 16 Topographic Map HOJA 5941 Official topographic map HOJA 5941 (1:100,000, contour interval 40 m) produced in Map 17 Topographic Map HOJA 6041 Official topographic map HOJA 6041 (1:100,000, contour interval 40 m) produced in mapcompilation Page 1

2 Map 1 (Jahn, 1925) Microfilm scan of Jahn s original map depicting glacier cover in the Sierra Nevada de Mérida (Jahn, 1925) in 1910/1911 (scale 1:100,000). This remained effectively the only map showing approximate glacier extents in Venezuela until the mapping efforts by Schubert (1972, 1992, 1998). Alfredo Jahn (1867 to 1940) was a civil engineer, surveyor, botanist, geographer, avid mountaineer, and prolific map maker (for example Lake Valencia, cf. Crist and and Chardon, 1941, their Fig. 2) and recorded the first ascent of Pico Humboldt on 16 January 1911 via the Sievers Glacier. Jahn also conducted some of the first official elevation determinations in the Sierra Nevada de Mérida (e.g. Jahn, 1907) and was responsible for lake level measurements in Lake Valencia between 1905 and 1938 (Crist and Chardon, 1941; Gschwendtner, 1963). Blumenthal (1923, Page 221) considered this map the baptism of the Sierra Nevada de Mérida as it provided, for the first time, the names and elevations of the mountains. It is important to note that the names used for most glaciers and certain lakes in the Sierra Nevada de Mérida are somewhat inconsistent and have changed over time, making it sometimes difficult to compare the work from different authors (cf. Federici and Pappalardo, 2010). mapcompilation Page 2

3 Jahn (1925) mapped the entire Pico Espejo summit and ridge area as covered by the Espejo Glacier that extended westward into the Laguna Espejo valley/cirque to an elevation of about 4,500 m asl (Schubert, 1992). This matches approximately the glacier extent depicted in the Goering painting created between 1864 and 1874 (cf. Schubert, 1984, Fig. 4). Jahn named many of the glaciers in the Sierra Nevada de Mérida in honor of previous explorers (Schubert, 1992). Schubert (1972, 1992, 1998), unfortunately, re-named many of the glaciers in the Sierra Nevada de Mérida using the local geographic names of the valleys they occupied during the Last Glacial Maximum, creating some confusion and inconsistencies in the literature. Schubert (1972) separated what Jahn mapped as the Burgoin Glacier into the West and North Glacier to designate their approximate aspects. The West Glacier faces more-or-less due west and would extend into the Laguna Espejo cirque. The North Glacier faces northwest and would extend into an adjacent cirque and valley. Schubert (1992, 1998) reintroduced the new Espejo Glacier, matching approximately Jahn s Burgoin Glacier and Schubert s own West and North Glacier (Schubert, 1972). mapcompilation Page 3

4 Map 2: Blumenthal (1923) mapcompilation Page 4

5 Blumenthal (1923) included this simple sketch map of the Sierra Nevada de Mérida based on his travels in The map was clearly not intended to accurately depict the shapes of glacier, but rather to serve as a guide for hiking and climbing. This map was deemed highly inaccurate by Gunther (1940). Blumenthal was engaged in geologic mapping for petroleum exploration and thus presumably a competent cartographer. Some of the perceived inaccuracies may therefore reflect glacier recession between Blumenthal s visit in 1922 and Gunther s expeditions in 1939 and mapcompilation Page 5

6 Map 3 (Gunther, 1940, 1941a) mapcompilation Page 6

7 Gunther s map (Gunther, 1940, 1941a) depicts glacier extent in the Sierra Nevada de Mérida after Jahn (1925) and supplemented by Gunther s own observations and measurements during two climbing expeditions in 1939 and 1940 (Gunther 1940, 1941a, b). Gunther used the same glacier names as Jahn (1925) and it is interesting to compare both maps. Gunther mapped the Espejo Glacier considerably smaller than Jahn as essentially limited to the western side of the Pico Espejo summit ridge area (cf. Map 1) and not extending too far towards Laguna Espejo. This subtle difference is consistent with the well-documented asymmetry in glacier cover and glacier recession in the early part of the 20 th century in the Sierra Nevada de Mérida (cf. Sievers, 1908; Blumenthal, 1923; Schubert, 1992). The map also shows how the names used for certain lakes have changed: Laguna Verde Laguna El Suero Laguna Verde as mapped and described by Jahn (1925), Gunther (1940, 1941a, b), and Hanbury- Tracy (1944) is today called Laguna El Suero. However, the name Laguna Verde may have been quite reasonable at the time when the Laguna Verde Glacier (today: Humboldt Glacier) extended much closer towards the lake and glacial meltwater/sediment inflow may have caused the lake to exhibit a greenish color. Laguna Negra Laguna Verde Laguna Negra as mapped and described by Jahn (1925), Gunther (1940, 1941a, b), and Hanbury- Tracy (1944) is today called Laguna Verde, although the old name Laguna Negra seems more appropriate today as the lake is large, deep, and appears black. The old name Laguna Negra indicates or perhaps even emphasizes that the lake was not greenish in color (in contrast to Laguna Verde upstream). This may suggest that the lobe of the Humboldt Glacier descending towards the lake at the time did not cause sufficient glacial meltwater/sediment input to yield a greenish color. mapcompilation Page 7

8 Map 4 (Gunther, 1940) Highly-generalized close-up map of the glaciers located in the Pico Bolivar Massif based on Gunther s observations during a climbing expedition in February 1939 (Gunther, 1940). The sketch map is clearly not intended for glacier area determinations, but is very useful as an orientation map for climbers and hikers. The glacier names correspond to Jahn (1925) and Gunther (1941a). mapcompilation Page 8

9 Map 5 (Busk, 1964) Busk (1964) prepared this map of the Sierra Nevada de Mérida based on earlier maps by Jahn (1925), Gunther (1940, 1941a), other unpublished maps, personal observations, and conversations with local people. This map was obviously not designed to accurately depict contemporary glacier cover, but rather to serve as an orientation map for hikers, mountain climbers, and trout fishing. Sir Douglas Busk was the British Ambassador to Venezuela in the early 1960s and completed a rare winter weekend ascent of Pico Bolivar with Eric Shipton in 1963 (Band and Peck, 1991). mapcompilation Page 9

10 Map 6.1 (Schubert, 1972) Glacial-geomorphic and topographic map of the Pico Bolivar Massif prepared by Schubert (1972, Fig. 1). Map 6.2 is a close-up of the glaciers around Pico Bolivar. mapcompilation Page 10

11 Map 6.2 (Schubert, 1972) Glacial-geomorphic and topographic map of the Pico Bolivar summit and surrounding area prepared by Schubert (1972, Fig. 1). With this map Schubert introduced three new glacier names: West Glacier, North Glacier, and East Glacier. The Espejo Glacier as mapped by Jahn and Gunther obviously did not exist anymore in 1972 when Schubert was mapping around Pico Bolivar. Schubert separated what Jahn and Gunther mapped as the Bourgoin Glacier into the West and North Glacier to designate their approximate orientation. The West Glacier faces westward and would extend into the Laguna Espejo valley/cirque. The North Glacier faces northwest and would extend into the adjacent cirque and valley. The East Glacier was previously mapped as Karsten Glacier by Jahn and Gunther. The name Las Hermanas Glacier used on this map is also confusing. Schubert (1972) used it for the small eastern lobe of the Timoncito Glacier. Jahn, Blumenthal, and Gunther, however, mapped the Hermanas Glacier as a small separate and glacier from the Timoncito Glacier located a few km further to the east (cf. Map 4). However, these new names used by Schubert (1972) were revised again by Schubert (1992, 1998) when he introduced a series of new names for many of the glaciers in the Sierra Nevada de Mérida. mapcompilation Page 11

12 Map 7 (Schubert, 1972, Fig. 5) Schubert s 1972 map compared glacier cover in the Pico Bolivar / Pico La Concha Massifs between 1910 and This map is obviously too generalized for quantitative analysis, but allows useful qualitative comparisons: Pico El Toro was glacier-covered in 1910, but not anymore in This is consistent with other evidence (e.g. Blumenthal, 1923; Schubert, 1992). In 1868 reports indicated an ice thickness of between 8 and 16 m on the flanks of Pico El Toro. By 1890 deglaciation was on the way and rock patches were emerging from below the ice. By 1915 only a small remnant remained and by 1931 Pico El Toro was ice-free (after Schubert, 1992, Page 60). The Garza Glacier on the western side of Pico La Concha apparently still existed in 1972, whereas the Mucuy Glacier on the eastern side had already disappeared. Both glaciers existed in 1952 (Schubert, 1992, 1998). This makes sense in terms of their relative orientation and size. The Garza Glacier was larger than the Mucuy Glacier in 1910/11 (Jahn, 1925, Gunther, 1940, 1941a) and was located on the western side, protected from solar radiation by the diurnal cycle in cloud cover (cf. Flohn, 1968). The Garza Glacier had disappeared by 1991 (Schubert, 1998). The basic configuration of the four glaciers around Pico Bolivar in February 1972 was the same as on Schubert s detailed 1952 aerial photograph map (Schubert, 1992). mapcompilation Page 12

13 Map 8 (Schubert, 1992) Glacier distribution in the Sierra Nevada de Mérida in 1910/1911 (after Jahn, 1925) and in 1952 as mapped by Schubert (1992) from aerial photographs. Glacier-covered area in 1910 was about 10 km 2 and about 2.91 km 2 in 1952 (Schubert, 1992, 1998). The table below lists glacier names and area for individual glaciers (after Schubert, 1992, Table 1). Massif Schubert (1992) Jahn (1925) Area (km 2 ) Pico Bolivar 1) Espejo Glacier Espejo Glacier ) Timoncito Glacier Timoncito/Hermanas Glacier ) El Encierro Glacier Bourgoin Glacier ) El Encierro Glacier Karsten Glacier 0.10 Pico La Concha 1) Ño León Glacier Garza Glacier ) Coromoto Glacier W-Remnant Mucuy Glacier 0.07 Pico Humboldt Pico Bonpland (1, 2) Coromoto Glacier E-Remnant 3) Siniguis Glacier Sievers Glacier 4) Nuestra Señora Glacier Plazuela Glacier Laguna Verde Glacier Codazzi Glacier 2.03 mapcompilation Page 13

14 Note that the summit of Pico Bonpland is marked incorrectly on this map. The actual summit location is about 1.5 km further to the southwest on the ridge extending northwest towards Pico La Concha (i.e. separating Glacier #3 and #4). Unfortunately, Schubert (1992) decided to rename and redefine many of the glaciers in the Sierra Nevada de Mérida from the original names used by Jahn (1925) and Gunther (1940, 1941a). In addition, Schubert s map and associated table contain several errors and inconsistencies. First, Schubert s new Espejo Glacier is not what Jahn and Gunther had mapped as the original Espejo Glacier, but rather what they mapped as the Bourgoin and Espejo Glacier. Second, Glacier #3 was mapped by Jahn and Gunther as the Karsten Glacier, not as the Bourgoin Glacier. Finally, Glacier #4 was mapped in combination with Glacier #3 by Jahn and Gunther as the Karsten Glacier (western and eastern section). Pico Bolivar Massif Schubert (1992) reintroduced the new Espejo Glacier matching approximately what Jahn and Gunther mapped as the Bourgoin and Espejo Glacier and what Schubert (1972) mapped as the West and North Glacier (Schubert, 1972). The original Espejo Glacier covering the Pico Espejo summit and ridge area had disappeared by The remnants of the new Espejo Glacier or old North Glacier are today still visible from downtown Mérida as two small ice/firn patches. Jahn (1925) and Schubert (1972) distinguished between the Timoncito Glacier and its easterly neighbor the Hermanas Glacier, whereas Schubert (1992) combined them. The original Hermanas Glacier (cf. Map 4) as mapped by Jahn, Blumenthal, and Gunther had more-or-less disappeared by 1952 and Schubert (1972) introduced the name Las Hermanas Glacier for what was essentially the smaller eastern lobe of the Timoncito Glacier. Schubert (1992) changed the name of the western section of the Karsten Glacier to El Encierro Glacier in reference to Laguna Del Encierro and associated stream. Schubert (1992) introduced the name El Encierro Glacier for the small glacier east of the (other) El Encierro Glacier. In the past, the El Encierro Glacier was mapped as the Karsten Glacier and consisted of a western section on the north side of Col Bourgoin and a smaller eastern section (mapped but unnamed on the map by Schubert, 1972) below and east of La Columna South Peak towards Pico La Concha. Pico La Concha Massif Schubert (1992) introduced the name Ño León Glacier for what Jahn and Gunther mapped as the Garza Glacier. Schubert (1992) introduced the name Coromoto Glacier W-Remnant for what Jahn and Gunther mapped as the Mucuy Glacier. Pico Humboldt and Pico Bonpland Massif Schubert (1992) introduced the name Siniguis Glacier for what Jahn and Gunther mapped as the Sievers Glacier on the southeastern side of Pico Humboldt (= the route Jahn used for his first ascent of Pico Humboldt on 16 January 1911). Schubert (1992) introduced the name Coromoto Glacier E-Remnant to combine what Jahn mapped separately as the Laguna Verde Glacier and Codazzi Glacier. The name Laguna Verde Glacier makes sense as it extends towards Laguna Verde, which is today called Laguna El Suero. Gunther, on the other hand, did not explicitly label the Laguna Verde Glacier on his map but used the name Humboldt Glacier in his papers for what Jahn mapped as the Laguna Verde Glacier. The Humboldt Glacier today is the remnant of the Laguna Verde Glacier as mapped by Jahn or the Humboldt Glacier as described by Gunther and Hanbury-Tracy. Schubert (1992) introduced the name Nuestra Señora Glacier for the glacier mapped by Jahn and Gunther as Plazuela Glacier on the southwestern side of Pico Bonpland. mapcompilation Page 14

15 Map 9 (Schubert, 1998) Schubert s 1998 map is a reproduction and generalization of his more detailed map from The accompanying table list glacier names, glacier area (in 1952), and glacier appearance in January 1991 for individual glaciers (cf. Map 10). mapcompilation Page 15

16 Map 10 (Schubert, 1998) This map included in Schubert (1998) depicts the distribution of glaciers in the Sierra Nevada de Mérida in 1952 based on aerial photographs. The accompanying table further lists glacier names, glacier area (in 1952), and subjective glacier appearance in January 1991 based on fieldwork and ground photographs. In the case of the Coromoto Glacier East Remnant, Schubert used a Landsat 2 satellite image from 29 January Unfortunately, Schubert changed the glacier numbering system with respect to his 1992 map (Schubert, 1992). In addition, many glacier names have changed over the last 100 years (cf. Map 8) and there are some inconsistencies in the literature regarding the precise spatial meaning of some glacier names. Note that the summit of Pico Bonpland is again marked incorrectly on this map. The actual summit location is about 1.5 km further to the southwest on the ridge extending towards Pico La Concha (i.e. separating Glacier #9 and #10). Glacier Appearance in January 1991 (after Schubert, 1998, Table 1) Glacier Name Appearance in 1991 Espejo Gl. (1) Melted into 2 small firn patches Timoncito Gl. (2) Almost completely disappeared El Encierro Gl. (3) Lost at least 50 percent of its area El Encierro Gl. (4) Retreated Ño León Gl. (5) Completely disappeared Coromoto Gl. West Remnant (6) Completely disappeared Coromoto Gl. East Remnant (7, 8) Retreated Siniguis Gl. (9) Retreated Nuestra Señora Gl. (10) Completely disappeared mapcompilation Page 16

17 The two small ice/firn patches remnants of the new Espejo Glacier (Schubert, 1992) or the old North Glacier as mapped by Schubert (1972) are still visible from the cable car line and downtown Mérida, but not from the summit of Pico Espejo. The two El Encierro Glaciers mapped by Schubert (1992, 1998) used to be known as the Karsten Glacier (western and eastern section) as mapped by Jahn and Gunther. The two glaciers in the Pico La Concha Massif existed in 1952 and had both disappeared by Glacier #5 still existed in 1972 (Schubert, 1972). See comments for Map 8 in reference to the glaciers in the Pico Humboldt/Pico Bonpland Massif. mapcompilation Page 17

18 Map 11 (Mahaney et al., 2000) The glacier outlines and glacier names shown here are based on a map for the Parque Nacional Sierra Nevada Sector Sierra Nevada De Merida Mapa Para Excursionistas (see Map 14). This map included three new glacier names: Glacier Este is used here for what Jahn and Gunther mapped as the Codazzi Glacier and Schubert mapped as the Coromoto Glacier East Remnant. Glacier de La Corona is used here for what is called today the Humboldt Glacier, Jahn mapped as the Laguna Verde Glacier, Gunther described as the Humboldt Glacier, and Schubert mapped as the Coromoto Glacier East Remnant. The name Glacier de La Corona is reasonable as the Pico Humoldt/Pico Bonpland Massif used to be known as the Corona Group (e.g. Blumenthal, 1923; Jahn, 1925; Gunther, 1940, 1941a, b). Glacier La Concha is used here for what Jahn and Gunther mapped as the Garza Glacier and Schubert mapped as the Ño León Glacier. Glacier extent and shape shown on this map are grossly inaccurate. mapcompilation Page 18

19 Map 12 (Mahaney et al., 2009) Annotated 1952 aerial photograph map of the Pico Humboldt/Pico Bonpland Massif. B = Bonpland Lobe C = Center Lobe N = Northern Lobe (= Codazzi Glacier after Jahn and Gunther) Today (2009/2011) the Northern Lobe (or Codazzi Glacier) has disappeared. The Center and Bonpland Lobe (of the Humboldt Glacier) have receded considerably. mapcompilation Page 19

20 Map 13 (Mahaney et al., 2009) Mahaney et al. (2009) included this simple sketch map of the Pico Humboldt foreland. The glacier extent shown here was presumably approximated from the 1952 aerial photographs (see Map 12). mapcompilation Page 20

21 Map 14 Section of the map Parque Nacional Sierra Nevada Sector Sierra Nevada De Merida Mapa Para Excursionistas (1:50,000). Glacier extent and shape shown on this map are grossly inaccurate. mapcompilation Page 21

22 Map 15 Section of topographic map NC Merida (1:250,000, contour interval 40 m) produced in 1978 based on 1:100,000 scale topographic maps from 1964 and Glacier extent and shape shown on this map are grossly inaccurate. mapcompilation Page 22

23 Map 16 Section of topographic map HOJA 5941 (1:100,000, contour interval 40 m) produced in 1977 based on aerial photography acquired between 1960 and Glacier extent and shape shown on this map are grossly inaccurate. mapcompilation Page 23

24 Map 17 Section of topographic map HOJA 6041 (1:100,000, contour interval 40 m) produced in 1977 based on aerial photography acquired in Glacier extent and shape shown on this map are grossly inaccurate. mapcompilation Page 24