𝗕𝗮𝘀𝗶𝗻 𝗧𝘆𝗽𝗲𝘀

1. Divergent Basins (Extensional Basins)

Form due to crustal extension and thinning, commonly associated with rifting and continental breakup.

Examples: Rift basins, passive margin basins

a) Rift Basins

Develop along extensional fault zones where the lithosphere is stretched.

Characterized by normal faults, grabens, and half-grabens.

Common in early-stage continental breakup (e.g., East African Rift System, North Sea Rift).

Petroleum Significance: Excellent source rocks (lacustrine shales) and structural traps (fault-bounded reservoirs).

b) Passive Margin Basins

Found along continental margins after rifting stops and seafloor spreading begins.

Thick sequences of sediments accumulate due to thermal subsidence.

Examples: Gulf of Mexico, West African Margin.

Petroleum Significance: Rich in organic-rich marine shales (source rocks) and large sandstone reservoirs.

2. Convergent Basins (Compressional Basins)

Form due to plate collision and crustal shortening.

Examples: Foreland basins, forearc basins, backarc basins.

a) Foreland Basins

Develop adjacent to mountain belts due to crustal loading by orogenic (mountain-building) processes.

Examples: Western Canada Sedimentary Basin, Persian Gulf Basin.

Petroleum Significance: Thick sedimentary sequences with excellent reservoirs and traps.

b) Forearc Basins

Form between an oceanic trench and a volcanic arc in subduction zones.

Examples: Peru-Chile Forearc Basin, Japan Forearc Basin.

Petroleum Significance: Complex depositional environments with potential gas accumulations.

c) Backarc Basins

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Located behind volcanic arcs, formed due to slab rollback and extension.

Examples: Sea of Japan, South China Sea.

Petroleum Significance: Potential hydrocarbon-bearing sedimentary sequences.

3. Transform Basins (Strike-Slip Basins)

Develop along strike-slip fault zones, where crustal blocks move laterally.

Examples: San Andreas Fault Basin, Dead Sea Basin.

Petroleum Significance: Contain localized pull-apart basins with high sedimentation rates and hydrocarbon potential.

4. Intracratonic Basins

Form within stable continental interiors, often due to slow thermal subsidence.

Examples: Williston Basin (USA), Illinois Basin.

Petroleum Significance: Long-lived source rock maturation, leading to extensive hydrocarbon accumulations.

5. Cratonic Rift and Failed Rift Basins (Aulacogens)

Ancient rift basins that did not evolve into full ocean basins.

Examples: West Siberian Basin, Reelfoot Rift (USA).

Petroleum Significance: Preserve thick organic-rich sediments suitable for oil and gas generation.

Comments

REMOTE SENSING INDICES

Remote sensing indices are band ratios designed to highlight specific surface features (vegetation, soil, water, urban areas, snow, burned areas, etc.) using the spectral reflectance properties of the Earth's surface. They improve classification accuracy and environmental monitoring. 1. Vegetation Indices NDVI – Normalized Difference Vegetation Index Formula: (NIR – RED) / (NIR + RED) Concept: Vegetation reflects strongly in NIR and absorbs in RED due to chlorophyll. Measures: Vegetation greenness & health Uses: Agriculture, drought monitoring, biomass estimation EVI – Enhanced Vegetation Index Formula: G × (NIR – RED) / (NIR + C1×RED – C2×BLUE + L) Concept: Corrects for soil and atmospheric noise. Measures: Vegetation vigor in dense canopies Uses: Tropical rainforest mapping, high biomass regions GNDVI – Green Normalized Difference Vegetation Index Formula: (NIR – GREEN) / (NIR + GREEN) Concept: Uses Green instead of Red ...

Energy Interaction with Atmosphere and Earth Surface

In Remote Sensing , satellites record electromagnetic radiation (EMR) that is reflected or emitted from the Earth. Before reaching the sensor, radiation interacts with: The Atmosphere The Earth's Surface These interactions control how satellite images look and how we interpret them. I. Interaction of EMR with the Atmosphere When solar radiation travels from the Sun to the Earth, four main processes occur: 1. Absorption Definition: Absorption occurs when atmospheric gases absorb radiation at specific wavelengths and convert it into heat. Main absorbing gases: Ozone (O₃) → absorbs Ultraviolet (UV) Carbon dioxide (CO₂) → absorbs Thermal Infrared Water vapour (H₂O) → absorbs Infrared Concept: Atmospheric Windows These are wavelength regions where absorption is very low, allowing radiation to pass through the atmosphere. Remote sensing depends on these windows. For example, satellites like Landsat 8 use visible, near-infrared, and thermal bands located in atmospheric windows. 2. Trans...

Atmospheric Window

The atmospheric window in remote sensing refers to specific wavelength ranges within the electromagnetic spectrum that can pass through the Earth's atmosphere relatively unimpeded. These windows are crucial for remote sensing applications because they allow us to observe the Earth's surface and atmosphere without significant interference from the atmosphere's constituents. Key facts and concepts about atmospheric windows: Visible and Near-Infrared (VNIR) window: This window encompasses wavelengths from approximately 0. 4 to 1. 0 micrometers. It is ideal for observing vegetation, water bodies, and land cover types. Shortwave Infrared (SWIR) window: This window covers wavelengths from approximately 1. 0 to 3. 0 micrometers. It is particularly useful for detecting minerals, water content, and vegetation health. Mid-Infrared (MIR) window: This window spans wavelengths from approximately 3. 0 to 8. 0 micrometers. It is valuable for identifying various materials, incl...

Landsat band composition

Short-Wave Infrared (7, 6 4) The short-wave infrared band combination uses SWIR-2 (7), SWIR-1 (6), and red (4). This composite displays vegetation in shades of green. While darker shades of green indicate denser vegetation, sparse vegetation has lighter shades. Urban areas are blue and soils have various shades of brown. Agriculture (6, 5, 2) This band combination uses SWIR-1 (6), near-infrared (5), and blue (2). It's commonly used for crop monitoring because of the use of short-wave and near-infrared. Healthy vegetation appears dark green. But bare earth has a magenta hue. Geology (7, 6, 2) The geology band combination uses SWIR-2 (7), SWIR-1 (6), and blue (2). This band combination is particularly useful for identifying geological formations, lithology features, and faults. Bathymetric (4, 3, 1) The bathymetric band combination (4,3,1) uses the red (4), green (3), and coastal bands to peak into water. The coastal band is useful in coastal, bathymetric, and aerosol studies because...

Landsat 8 Band designation and Band Combination.

Landsat 8 Band designation and Band Combination. Landsat 8-9 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) Bands Wavelength (micrometers) Resolution (meters) Band 1 - Coastal aerosol 0.43-0.45 30 Band 2 - Blue 0.45-0.51 30 Band 3 - Green 0.53-0.59 30 Band 4 - Red 0.64-0.67 30 Band 5 - Near Infrared (NIR) 0.85-0.88 30 Band 6 - SWIR 1 1.57-1.65 30 Band 7 - SWIR 2 2.11-2.29 30 Band 8 - Panchromatic 0.50-0.68 15 Band 9 - Cirrus 1.36-1.38 30 Band 10 - Thermal Infrared (TIRS) 1 10.6-11.19 100 Band 11 - Thermal Infrared (TIRS) 2 11.50-12.51 100 Vineesh V Assistant Professor of Geography, Directorate of Education, Government of Kerala. https://www.facebook.com/Applied.Geography http://geogisgeo.blogspot.com

Vineesh V, Geography

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