7#T$VT""""""."""" ###"#6x"# ##*$"####$9######.c.Andes Mountains, South America Titles of Investigations: I. SIR-C/X-SAR Analysis of Topography and Climate in the Central Andes II. SIR-C/X-SAR Radar Investigations of Volcanism and Tectonism in the Northern Andes Principal Investigators: I. Brian Isacks Cornell University II. Chuck Wood University of North Dakota Site Description: The Andes Mountains of South America provide an ideal laboratory to study the effects of both modern and Quaternary climate changes. The mountain belt traverses a latitudinal transect of over 60 from equatorial to sub-polar regions. Since at least four million years ago, the glaciers and icesheets of the Andes have expanded and contracted in response to the Earth's changing climate. These changes have left an indelible geomorphic signature on the landscape that can be used to reconstruct changes in temperature and precipitation that caused the glacial advances and retreats. In addition, the modern glacier movements in the Andes provide a valuable record of historic and ongoing climate change in the region. During the last 100 years, most glaciers along the entire range of the Andes have shown marked retreat. The Patagonian Lake District in Argentina and Chile is of special interest because it includes South America's most extensive modern, as well as past, glaciers and ice fields. The regions glacial history is one of the most studied in all of the Andes (e.g., Caldenius, 1932; Mercer, 1976, 1983; Morner and Sylwan, 1989). Throughout the Quaternary, the Patagonian ice caps and glaciers have had the largest volume of ice in the southern hemisphere outside of Antarctica (and only exceeded by the ice fields of southeast Alaska and the Karakorum in the northern Hemisphere). Previous glaciations produced a series of extensive moraines, the earliest of which is at least 700,000 years old. From these moraines it is possible to infer the extent and timing of the previous glaciations and thereby reconstruct the history of climate change in this region. The semi-arid climate of the region resulting in sparse vegetation and slow weathering rates make it possible to use SIR-C/X-SAR to estimate moraine chronology from space. Moraine sequences can be differentiated with SAR because of the correlation of surface roughness with moraine age. Older moraines become smoother through time as a result of boulder weathering and soil development; in contrast, the angular and more dense boulder distribution of the younger moraines presents a rougher surface. The ability of SAR to categorize moraines based on age has been demonstrated through analysis of airborne SAR images of the Mono Basin moraines in California. The area was chosen as a proof-of-concept site because of its similarity to the Patagonian site with expressions of multiple glaciation and sparse vegetation. The Mono Basin moraines are well studied with established chronologies and have been dated by cosmogenic exposure with 36Cl. In an effort to further constrain the timing of glaciations and provide calibration for the radar measurements, the Cornell Andes Project collected samples from boulders on all four of the major moraine sequences (Figure 1) in the Patagonian Lago Buenos Aires area. These samples are now being dated with the 36Cl exposure dating technique. SIR-C/X-SAR images of the moraines in the Andes will be analyzed with the techniques established by the Cornell Andes Project to obtain ages for the moraines. The site will act as a moraine age calibration site for the Andes enabling SAR dating technique to be extended to other Andean moraines imaged by SIR-C/X-SAR and future SAR missions. From this cornerstone location an extensive glacial chronology for the Andes may be constructed from spaceborne satellites supplying new information regarding the dynamics of past global climate change. The two Patagonian ice caps adjacent to the supersite (and criss-crossed by the SIR-C/X-SAR swaths) are among the least studied of the earths major alpine snow and ice field due to remoteness and cloud cover, although some work has been done (e.g. Aniya, 1988). SIR-C/X-SAR images across the Patagonian Lake District will provide a powerful means to determine the present-day glacier and snowline extents, and to estimate equilibrium line altitudes (ELAs) on glaciers by differentiation of snow and ice facies. Estimation of the modern regime, required for comparison with Quaternary condition to infer paleotemperatures and paleoprecipitation, will also contribute important baseline data for measurements of future changes in this climatically sensitive region. Objectives: I. a) Calibrate radar measurements of the ages of glacial moraines. b) Determine modern and Pleistocene snow-line altitudes and gradients along Andean latitudinal transect. c) Provide new baseline measurements of the state of the Patagonian ice caps and glaciers. II. a) Increase understanding of the volcano-tectonic history of Andes mountain range by testing and extending the volcano-tectonic segmentation model. b) Develop radar models for detecting and mapping pyroclastic and mudflow deposits at dangerous volcanoes of the Andes. Field Measurements: I. a) Additional 36Cl measurements of moraine ages. b) Measurement of images moraine surface roughness. c) Observations of snow and ice conditions at time of imaging. Wood please provide if applicable Crew Observations: 1) Crew Journal: Monitor dust storms and determine the extent of the snow line and glaciers. 2) Cameras: Hercules and Hasselblad will be used to photograph the site. Stereo and low sun angle images are requested. Coverage Requirements: Two polarimetric swaths crossing morainal sequences of Lago Buenos Aires. Polarimetric swaths crossing ice caps. Anticipated Results: I. a) Determination of the timing of late Quaternary Andean glacial advances. b) New information about the degree of correlation between Northern and Southern Hemisphere Quaternary climate change. c) Baseline data for determination of future changes in volumes of Patagonian snow and ice. II. a) Greatly improve geologic knowledge of poorly mapped, frequently cloud-covered, volcanically active arc; b) Increase understanding of a seismically unusual subduction setting; c) Develop an optimal interpretation of radar data for detection and mapping of pyroclastic/lahar deposits in tropical environments; d) Improve understanding of distribution and character of poorly mapped deposits at Ruiz and other explosive volcanoes in the area; and e) Recognize prehistoric pyroclastic deposits around other Andean volcanoes thereby increasing awareness of volcanic hazards. u0`?!"$=>?M`a -9:abuw%I[\45KPSTW @    *"#$>?  !1NOab 1--.:;KLabvw%&߻譟uuuu ! 8@ !8@ ! x@ ! x@ ! 0@! 0 !L !  !  ! 0@ 0@.&HI\]45LM(*stEFRSTȺȺȺȺȺȺ! ! 8@ ! 8@ ! 0@! 0 ! 0@! 0 :New York 10 point,timesCourier , TT MT&tW&T ! HH(FG(HH(d'@=/RBH -:LaserWriter PalatinoSSS(9Mission SummarySIR-CED Karl Erickson Karl Erickson