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Geog319RmSns > Soils and Minerals > Flashcards

Soils and Minerals Flashcards

1
Q

Why is RS limited for soils?

A
  • Dense vegetation often on top of soil
  • Needs exposed soils and minerals
  • Visual good for drainage basins and Earth structures
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2
Q

Geobotany

A
  • Infer mineralogical or soil type based on overlying vegetation
  • Vegetation as proxy
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3
Q

What is the greatest enemy to measuring soils radiance?

A

Vegetation

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4
Q

Ltotal = ?

A

Lp plus Ls plus Lv

- Ls and Lv of interest for bare soil

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5
Q

How deep into soil does Ls go?

A
  • 1/2 of lambda deep
  • ex. 0.55micrometers = 0.27micrometers depth of penetration (hair is 100micrometers for comparison)
  • O horizon
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6
Q

How deep into soil does Lv go?

A
  • A few cm

- O and A horizons

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7
Q

Ls and Lv are a function of?

A
  • Soil texture (grain size/roughness)
  • Soil moisture
  • Organic matter content
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8
Q

What happens to penetration with depth of Organic layer horizon?

A
  • Deep O layer = fully attenuates and will not penetrate deeper soil
  • Thin O layer = more light penetration and better Lv radiance
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9
Q

Soil texture

A
  • Percent sand, silt, clay in soil
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10
Q

Sand soil

A
  • 2mm

- water can percolate easily in large air spaces

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11
Q

Silt and clay soil

A
  • Clay 0.002mm
  • Silt 0.05mm
  • Retention of soil capillary water = more water
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12
Q

What happens as grain size increases?

A
  • Probability of photon absorption increases
  • Due to larger internal path of grain
  • Smaller grain has more surface (reflection) than volume (absorption)
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13
Q

Graph of dry bare silt vs. sand

A
  • Reflectance increases with increasing wavelengths throughout Vis, NIR, and MIR
  • Sand less reflection than silt b/c of more volume in larger grain absorbing
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14
Q

Dry soil

A
  • Ls specular reflection
  • Increase scatter btwn grains
  • Lv volume reflectance penetrates into particle and can be absorbed
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15
Q

Wet soil

A
  • Specular reflection
  • Volume reflectance
  • Absorption by water in interstitial space and capillary water at familiar peaks (0.76, 0.97, 1.1, 1.4, 1.9, 2.7)
  • Darker appearance b/c water absorbs IR and lowers reflectance
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16
Q

What is the amount of moisture held in a soil layer a function of?

A
  • Function of Soil texture (grain size)
  • Smaller particle = greater ability to hold more moisture for longer b/c of capillary water
  • Sand drains rapidly
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17
Q

What effect does increased moisture have on reflectance?

A
  • More valleys in reflectance from water absorption
  • Soil will appear darker
  • Reflectance will decrease, absorption increase
18
Q

Where are the ‘valleys’ of absorption in sand and what happens as moisture increases?

A
  • Dry soil has negligible valleys
  • Increase moisture and reflectance decreases
  • Valleys appear at 1.4, 1.9, 2.7, the typical water absorption locations
19
Q

Where are the ‘valleys of absorption in clay and what happens with increasing moisture?

A
  • Dry clay has valleys at 1.4 and 2.2 regardless of moisture content
  • 2.2 micrometers is unique to clay b/c of hydroxyl molecule not found in sands absorbs at this wavelength
  • As moisture increases, reflectance decreases and typical water absorption valleys become more pronounced
20
Q

At what wavelength does clay have unique absorption because of the hydroxyl molecule?

A
  • 2.2
  • But also less unique at 1.4 (similar to water)
  • 1.4 will be seen without water content and will become more pronounced with increasing moisture
21
Q

Presence of organic material causes what in soil reflectance?

A
  • Reduction in reflectance due to increased absorption
  • Visible wavelengths will see increased absorption
  • Soil appears darker
22
Q

What will happen if organic matter is burned off?

A

Reflectance will increase, especially at shorter wavelengths

23
Q

Where does Organic Matter absorb more?

A
  • Blue spectrum

- Increase OM and absorption at short wavelengths increases

24
Q

What can the absorption of water in soil infer?

A
  • Soil moisture content
  • Water stressed fields
  • Use for precision farming, algorithm in almost real-time w/ satellite data (mostly in developed countries)
25
Q

What are variables that affect ratio of organic?

A
  • Soil composition, moisture content, organic content, mineral content, soil texture
26
Q

What does mineral detection require?

A
  • High spectral resolution
  • Detail in SWIR
  • Spectral absorbance happens at specific, small locations for different minerals
  • W/o hyperspectral, small detailed features would be lost
  • Most features in SWIR
27
Q

AVIRIS

A
  • Airborne Visible Infrared Imaging Spectrometer
  • NASA
  • 224 contiguous spectral channels (bands)
  • Wavelengths 400 - 2500nm
28
Q

GERIS

A
  • 63 bands
  • Hyperspectral
  • Not great but better than Landsat
29
Q

How should a company interested in exploring for minerals go bout doing that?

A
  • Use hyper spectral because Landsat would be useless
  • Airborne would be best but is expensive
  • Use USGS spectral library for minerals
30
Q

Why is SWIR and thermal important for mineral exploration?

A
  • SWIR shows many small details specific to individual minerals
  • Thermal bands important because some minerals emit, not reflect
31
Q

ASTER

A
  • Advanced Spaceborne Thermal Emission and Reflection Radiometer
  • Designed for geological exploration by Japanese
  • Free, USGS website
  • 26m resolution
  • Broad Vis bands b/c not goal of platform
  • Narrow SWIR and TIR
32
Q

What band combination should be used for ASTER mineral data?

A
  • RGB all SWIR
33
Q

Where are ASTER bands located?

A
  • Broad Vis
  • Many Narrow SWIR and TIR to see minerals detailed absorption peaks
  • In atmospheric windows to avoid atm water absorption
34
Q

Compare and contrast ASTER, Hyperion and Landsat ETM

A
  • ASTER designed for minerals with broad
    Vis and many narrow SWIR and TIR
  • Hyperion has many more narrow bands from Vis to SWIR but does not reach TIR
  • Landsat has broad bands in Vis, SWIR and TIR but will not give small details of minerals
35
Q

What was ASTER, Landsat and MODIS designed for?

A
  • ASTER: minerals b/c of many narrow SWIR and TIR
  • Landsat: Vegetation b/c broad bands
  • MODIS: oceanographic b/c of narrow bandwidths in Vis, B and G in particular
36
Q

What is ASTER band 6 and 8 designed for? 10, 11, 12?

A

6: Clays (kaolinite, gypsum)
8, 14: Carbonates (limestones, dolomites)
10, 11, 12: Silicates

37
Q

Geobotany

A
  • Vegetation spectral changes can be related to lithology, soil chemistry
  • Helps ID underlying soil when vegetation density covers it
  • ex. Copper enriched vegetation
38
Q

How does Geobotany work

A
  • Vegetation changes in presence of heavy metals or alteration zones
  • Accumulation of heavy metals may stress vegetation and shift red-edge
  • May be evident as abrupt changes in plant species indicating lithological change rather than stress
  • Lack of vegetation b/c of toxic metals
  • Basically, some veg uptakes compounds, some veg changes depending on minerals
39
Q

Indicator plants

A
  • Grow in soils enriched by certain elements
40
Q

What happens to Balsam fir and Red spruce in metal enriched soil?

A
  • Increased G reflectance for both
  • Balsam: NIR increase
  • Spruce: NIR decrease

Geog319RmSns (15 decks)

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