Week Fifteen Synopsis of Ch. 14: Soils: RS plays a limited role in the ID, inventory, & mapping of soils. Rocks & minerals: Emphasis is placed on understanding unique absorption bands associated with specific types of rocks & minerals using imaging spectroscopy Geology & geomorphology: RS can be used to extract geologic information including, structure, drainage patterns, & landforms

Soil Soils require in situ examination Soil RS works in ideal situations only Spectral reflectance characteristics via: Aerial photography Multispectral Hyperspectral A function of several characteristics: Soil texture (% sand, silt, clay) Soil moisture (dry, moist, saturated) Organic matter content Fe2O3 content Soil salinity Surface roughness

Soil: Texture and Moisture Increasing reflectance with increasing wavelength visible through middle-infrared

Soil: Texture and Moisture Smaller particles hold water better than larger ones (clay, silt, sand) As such, more water means more absorption and less reflectance

Soil: Texture and Moisture Higher moisture content in (a) sandy and (b) clayey soil results in decreased reflectance, especially in the water absorption bands (1.4,1.9, 2.7 μm). Question: Why are water absorption bands more active in clayey soil? 1.4, 1.9, 2.7 water absorption bands

Soil: Texture and Moisture More organics at surface means more absorption and lower spectral reflectance

Soil: Texture and Moisture Active radar 24 cm (L band) radar: > In dry sand can penetrate 1 – 2 m > Can penetrate thin moist sand 5 – 8 cm (C band) radar: > Can see extent of dry sand well

Soil: Organic Matter and Biological Soil Crusts Moss, algae, lichen, bare ground Fig. 14.9 Fig. 14.0

Soil: More… Iron oxide (Fig. 14-11). Salinity (Fig. 14-12) High reflectance in red Salinity (Fig. 14-12) More salt, more reflectance Can be confused with silty soils Surface roughness with radar Must be dry and devoid of veg. Sand = bright; clayey = dark Meshing of wavelength to clast size means more reflectance Fig. 14.9 Fig. 14.0

Rocks and Minerals: Imaging Spectroscopy Imaging spectrometers are ideal Optical properties vary in complex ways with wavelength > electronic absorption processes (unfilled electron shells) > crystal lattice vibration absorption processes Often, hyperspectral sensors are needed Refer to a spectral reflectance library > JPL’s Salisbury et al. 1991 > USGS Digital Spectral Library

Rocks and Minerals: Imaging Spectroscopy Many diagnostics for mineral ID are found in thermal infrared Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on Terra has: Band 6 for clay and hydrothermal discrimination Bands 8, 14 for carbonate discrimination Bands 10, 11, 12 for sulfates and silica

Geology: Lithology and Structure Focus on image interpretation (shape, pattern) Digitizing to characterize morphometric parameters (Table 14-1, pg. 525)

Geomorphology Sensors: Digital products: Aerial photography Radar Lidar Sonar Digital products: 2.X dimensional interactive image Oblique views Image draping

Geomorphology Geomorphometry: Application areas: Concave and convex slopes, curvature, flow accumulation, channel delineation, watershed partitioning, roughness More here and here Application areas: Tectonic geomorphology Subsidence and uplift Paleoglacial studies Coastal processes (hurricane erosion) Landform evolution theories Flood and other hazards mapping River migration (border issues)