Global Plate Tectonics and India Subcontinent

1. Global Plate Tectonics

The theory of Plate Tectonics explains how the Earth's lithosphere (the rigid outer shell) is broken into large pieces called plates.

Plates: These plates float over the softer, semi-molten layer beneath, called the asthenosphere.
Movement: Driven by heat from Earth's interior (mantle convection, ridge push, slab pull), plates move a few centimetres per year — about the speed your fingernails grow.
Boundaries: Where plates meet, we get different interactions:
1. Divergent boundaries – plates move apart (mid-ocean ridges, new crust formation).
2. Convergent boundaries – plates collide (mountains, subduction zones).
3. Transform boundaries – plates slide past each other (earthquakes).

Why it matters: This movement shapes continents, mountains, volcanoes, ocean basins, and earthquakes.

2. India's Place in Global Plate Tectonics

India's geologic story is one of the most dramatic and fast-moving continental journeys in Earth's history.

Past position: Around 150 million years ago (Mesozoic Era), India was part of the southern supercontinent Gondwanaland, along with Africa, Antarctica, Australia, and South America.
Breakup: About 120 million years ago, the Indian plate broke away and started moving northwards across the Tethys Ocean.
Fast motion: India moved unusually quickly — about 15–20 cm/year at times (triple the average speed of plates).
Collision: Around 50 million years ago, the Indian plate collided with the Eurasian plate.
Result: The Himalayas and the Tibetan Plateau began to rise — and they are still rising today.

3. Current Tectonic Setting of India

Plate boundaries around India:
- North: Convergent boundary with the Eurasian Plate → Himalayan orogeny (mountain building) and seismic activity in the Himalayan belt.
- West: Transform and convergent interactions with the Arabian Plate along the Owen Fracture Zone and Makran Subduction Zone (earthquake risks in Gujarat, Arabian Sea).
- East: Convergent boundary with the Burma Plate and Sunda Plate → Andaman–Nicobar volcanic arc and earthquakes.
- South: Surrounded by the Indian Ocean spreading ridges (divergent boundaries) in the southwest and southeast.
Seismic zones: India has four main seismic zones (II–V), with Zone V being the most active (NE India, Kashmir, Andaman–Nicobar).

4. Key Effects on India

Himalayan growth: Still rising ~5 mm/year; ongoing earthquakes.
Peninsular stability: Generally stable, but intraplate quakes occur (e.g., Latur, Koyna) due to ancient fault reactivation.
Volcanism: Andaman–Nicobar volcanic activity (Barren Island volcano).
Tsunamis: Risk from undersea earthquakes (2004 Indian Ocean tsunami).

Time Period	Event	Impact
~150 Ma	India part of Gondwanaland	Connected to Antarctica, Africa, Australia
~120 Ma	Broke away from Gondwanaland	Started moving north
~50 Ma	Collision with Eurasia	Formation of Himalayas, Tibetan Plateau
Present	Active convergence & seismicity	Earthquakes, mountain building, volcanism

Comments

History of GIS

1. 1832 - Early Spatial Analysis in Epidemiology: - Charles Picquet creates a map in Paris detailing cholera deaths per 1,000 inhabitants. - Utilizes halftone color gradients for visual representation. 2. 1854 - John Snow's Cholera Outbreak Analysis: - Epidemiologist John Snow identifies cholera outbreak source in London using spatial analysis. - Maps casualties' residences and nearby water sources to pinpoint the outbreak's origin. 3. Early 20th Century - Photozincography and Layered Mapping: - Photozincography development allows maps to be split into layers for vegetation, water, etc. - Introduction of layers, later a key feature in GIS, for separate printing plates. 4. Mid-20th Century - Computer Facilitation of Cartography: - Waldo Tobler's 1959 publication details using computers for cartography. - Computer hardware development, driven by nuclear weapon research, leads to broader mapping applications by early 1960s. 5. 1960 - Canada Geograph...

Pre During and Post Disaster

Disaster management is a structured approach aimed at reducing risks, responding effectively, and ensuring a swift recovery from disasters. It consists of three main phases: Pre-Disaster (Mitigation & Preparedness), During Disaster (Response), and Post-Disaster (Recovery). These phases involve various strategies, policies, and actions to protect lives, property, and the environment. Below is a breakdown of each phase with key concepts, terminologies, and examples. 1. Pre-Disaster Phase (Mitigation and Preparedness) Mitigation: This phase focuses on reducing the severity of a disaster by minimizing risks and vulnerabilities. It involves structural and non-structural measures. Hazard Identification: Recognizing potential natural and human-made hazards (e.g., earthquakes, floods, industrial accidents). Risk Assessment: Evaluating the probability and consequences of disasters using GIS, remote sensing, and historical data. Vulnerability Analysis: Identifying areas and p...

Supervised Classification

Image Classification in Remote Sensing Image classification in remote sensing involves categorizing pixels in an image into thematic classes to produce a map. This process is essential for land use and land cover mapping, environmental studies, and resource management. The two primary methods for classification are Supervised and Unsupervised Classification . Here's a breakdown of these methods and the key stages of image classification. 1. Types of Classification Supervised Classification In supervised classification, the analyst manually defines classes of interest (known as information classes ), such as "water," "urban," or "vegetation," and identifies training areas —sections of the image that are representative of these classes. Using these training areas, the algorithm learns the spectral characteristics of each class and applies them to classify the entire image. When to Use Supervised Classification: - You have prior knowledge about the c...

History of GIS

The history of Geographic Information Systems (GIS) is rooted in early efforts to understand spatial relationships and patterns, long before the advent of digital computers. While modern GIS emerged in the mid-20th century with advances in computing, its conceptual foundations lie in cartography, spatial analysis, and thematic mapping. Early Roots of Spatial Analysis (Pre-1960s) One of the earliest documented applications of spatial analysis dates back to 1832 , when Charles Picquet , a French geographer and cartographer, produced a cholera mortality map of Paris. In his report Rapport sur la marche et les effets du choléra dans Paris et le département de la Seine , Picquet used graduated color shading to represent cholera deaths per 1,000 inhabitants across 48 districts. This work is widely regarded as an early example of choropleth mapping and thematic cartography applied to epidemiology. A landmark moment in the history of spatial analysis occurred in 1854 , when John Snow inv...

Representation of Spatial and Temporal Relationships

In GIS, spatial and temporal relationships allow the integration of location (the "where") and time (the "when") to analyze phenomena across space and time. This combination is fundamental to studying dynamic processes such as urban growth, land-use changes, or natural disasters. Key Concepts and Terminologies Geographic Coordinates : Define the position of features on Earth using latitude, longitude, or other coordinate systems. Example: A building's location can be represented as (11.6994° N, 76.0773° E). Timestamp : Represents the temporal aspect of data, such as the date or time a phenomenon was observed. Example: A landslide occurrence recorded on 30/07/2024 . Spatial and Temporal Relationships : Describes how features relate in space and time. These relationships can be: Spatial : Topological (e.g., "intersects"), directional (e.g., "north of"), or proximity-based (e.g., "near"). Temporal : Sequential (e....

Vineesh V, Geography

Search This Blog