1. Davis – Geographical Cycle of Erosion (Time-Controlled Model) Proposed by: William Morris Davis Core Concept Davis proposed that landforms evolve through a sequential, time-dependent cycle following a single episode of rapid tectonic uplift . After uplift, erosion becomes the dominant geomorphic agent. Fundamental Assumptions Structure + Process + Time = Landscape form Uplift is rapid and followed by tectonic stability Denudation operates progressively through stages Landscape evolution is orderly and predictable Stages of the Cycle Youth Stage High relief and steep gradients Deep, narrow V-shaped valleys Active vertical erosion Presence of waterfalls and rapids Maturity Stage Maximum relief Valley widening through lateral erosion Well-developed drainage network Reduced interfluves Old Age Stage Low relief surface Extensive lateral erosion Broad floodplains Formation of a nearly level surface called a peneplain Key Terminologies Base level Graded river Peneplain Sequential develop...
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...