remote sensing, rocks and soils
DESCRIPTION
Remote Sensing, Rocks and Soils. Prospecting and Exploration. What we’re looking for is subtle Most rocks, even the most favorable, do not have extractable resources 1% of mineral occurrences are worth detailed study 1% of those are worth drilling 1% of those are worth mining. - PowerPoint PPT PresentationTRANSCRIPT
Remote Sensing, Rocks and Soils
Prospecting and Exploration• What we’re looking for is subtle• Most rocks, even the most favorable, do
not have extractable resources• 1% of mineral occurrences are worth
detailed study• 1% of those are worth drilling• 1% of those are worth mining
Geologic Map of
Wisconsin
Gravity Map of
Wisconsin
Gravity• Mean value about 9.8 m/sec2 = 1 g• About 0.5% smaller at equator than poles• Map unit = gal (for Galileo) = 1 cm/sec2
• Mean gravity = 980 gal• Maps contour in mgal = 10-6 g• Modern gravimeters can detect .001 mgal
variations (= 1 ppb)• A gravimeter is essentially a spring balance.
Gravimeter
Gravity Maps• Gravity varies by latitude due to earth’s
equatorial bulge and centrifugal force• Need altitude correction = 0.3 mgal/m = 3 x 10-7
g/m• Altitude only correction = Free-Air Anomaly Map• Correct for mass between you and sea level =
Bouguer Anomaly Map• Correct for variations in thickness of crust =
Isostatic Anomaly Map
Colorado Bouguer Map
Colorado Isostatic Map
Chicxulub Impact Basin Gravity Map
Gravity Mapping
• Simple corrections for latitude and altitude
• Density = Lithology• Can sense deep into
crust
• Gravimeters are basically sensitive spring balances
• Fragile• Prone to drift• Discrete data points• Labor intensive, low
detail
Magnetic Map of
Wisconsin
Geomagnetism • Magnetic field of Earth = 40 microtesla =
40,000 nt• Varies from 25 to 70 mt• Non-axial• Not centered on the earth• Varies over a human lifetime
Overall Magnetic Field of Earth
MAGSAT Map of Earth
Magnetic Mapping
• Corrections are complex and time variable
• No simple correlation with lithology
• Can’t sense deep into crust because heat destroys magnetism
• Magnetism is electromagnetic phenomenon
• Instruments can be purely electronic
• Can record continuously
• Can be extremely detailed
Gravity and Magnetic Mapping
• Greater sensing depth • Complex corrections• Greater detail possible
Gravity and Magnetic MappingGravity maps Magnetic Maps
Mechanical Instrument Instruments are purely electronic
Discrete readings Continuous readings
Less detail Great detail
Can sense to great depths Can sense only a few kilometers deep
Simple corrections for latitude and elevation
Complex corrections in time and space
Density correlates with rock type No simple correlation with rock type
SatelliteImage of Wisconsin
Grand Canyon
Lake Vostok,
Antarctica
Copper Mines, Iran
Saline Valley, California
The Moon
Mercury
Mars False Color View
Remote and Not
So Remote Sensing
Telling Minerals Apart
Martian Minerals?
Absorption Bands
Radar Interferometry: L’Aquila, Italy,
2009
Haiti, 2010
Haiti, 2010
Damage, Port au prince
Chile, 2010
Chile 2010
Chile, 2010, GPS
Ice Flow, Antarctica
Kilauea, Hawaii
Venus
Topography of Venus
Radar Map of Venus
Radar Map of Venus
Venus Gravity Maps
Gravity Map of Mars
Titan
Radar Image, Titan
Lakes on Titan
Sun Glint
Laser Rangefinder
Laser Reflector
LAGEOS
Herstmonceaux Castle (London)
• Latitude increasing (moving N)
• Longitude increasing (Moving E)
Lamont Earth Observatory
(Near New York)• Latitude increasing
(moving N)• Longitude decreasing
(Moving W)
Trans-Atlantic Plate Motion
• New York moving west at 15.4 mm/yr• London moving east at 16.6 mm/yr• Relative motion = 32 mm/yr
Churchill, Manitoba
• Latitude decreasing (moving S)
• Longitude decreasing (Moving W)
• Rising rapidly
Real-Time Plate Motions
Sturgeon Bay, Wisconsin