Himalayas Formation, Relief, and Structure - Geomorphology: Tectonic Plates, Mountain Building, and Landform Characteristics
Himalayas Formation, Relief and Structures
Formation Overview
The Himalayan mountain range and the Tibetan plateau were formed as a result of the collision between the Indian Plate and the Eurasian Plate, which began 40-50 million years ago and continues today.
Collision Impact:
Both plates have about the same rock density, preventing subduction.
Pressure from the collision caused thrusting upwards.
Resulted in the formation of the jagged Himalayan peaks.
Himalayas Formation
The Himalayas are the youngest mountain chain in the world.
Origin:
Formed from a geosyncline called the Tethys Sea.
Uplift occurred in phases.
Permian Period (250 million years ago):
The supercontinent Pangaea existed, consisting of:
Laurasia: Northern part, made up of present-day North America and Eurasia.
Gondwanaland: Southern part, made up of present-day South America, Africa, India, Australia, and Antarctica.
The Tethys Sea existed between Laurasia and Gondwanaland.
Rivers deposited sediments in the Tethys Sea.
These sediments were compressed due to the northward movement of the Indian Plate.
Resulted in folding and the eventual formation of the Himalayas.
Mount Everest: The summit is made of marine limestone from the ancient Tethys Sea.
The Indian plate continues to move northward at 5 cm/year, raising the Himalayas.
The Tibetan plateau was formed due to the upthrusting of the southern block of the Eurasian Plate.
The Indo-Gangetic plain was formed from the alluvium deposited by Himalayan rivers.
The Himalayas have a curved shape due to the maximum push at the ends of the Indian Peninsula.
Phases of Himalayas Formation
The Himalayas consist of three parallel ranges that emerged from the Himalayan Geosyncline (Tethys Sea) in six distinct phases.
Each phase marked a significant stage in the formation of the ranges.
6 Phases of Himalayas Formation
Phase 1 – 100 million years ago:
During the Cretaceous Period:
The Indian plate was located between 10⁰S and 40⁰S, over the Reunion hotspot.
The plate's movement towards the equator at a rate of 14 cm/year initiated the squeezing of the Tethys Sea.
Phase 2 – 71 million years ago:
Himalayan orogenesis began:
The Indian plate drifted northeast and collided with the Aravalli series.
Collision formed the Indus–Tsangpo Suture Zone (ITSZ), a compressional tectonic fault line.
Crustal doubling below Tibet created the high Tibetan plateau.
The Murree Foredeep and Shiwalik Foredeep were formed south of the ITSZ.
Phase 3 – The Drass Volcanic Arc (Oligocene Period):
Volcanic eruptions occurred:
In the Tethys crust, forming the Drass volcanic area.
Anti-clockwise rotation of the Indian plate released pressure in the west but squeezed Tethyan sediments in the east.
Marked the rise of the Tethyan Himalayas.
Phase 4 – Greater Himalayas Raised (30-35 million years ago):
Continued compression caused a major thrust:
Raised the Greater Himalayas.
The Main Central Thrust (MCT) was the compressional line that raised the Greater Himalayas.
Phase 5 – Rise of Lesser Himalayas (15-20 million years ago):
Sediments deposited in the Shiwalik foredeep were compressed:
Leading to the rise of the Lesser Himalayas during the Miocene.
The Boundary Thrust/Fault (MBT) separates the Greater and Lesser Himalayas.
Phase 6 – Rise of the Shiwalik Ranges:
Sedimentation by Himalayan rivers filled the Shiwalik foredeep:
Partial folding along the Himalayan Frontal Fault (HFF) led to the rise of the Shiwalik ranges.
Tibetan Plateau
The Tibetan Plateau:
Not part of the Himalayas but formed due to Himalayan orogeny.
Often referred to as the "Roof of the World" due to its high elevation.
Significance:
Serves as a major factor influencing the regional climate.
Acts as a barrier to the cold winds from the north, affecting weather patterns in the Indian subcontinent.
Indus–Tsangpo Suture Zone (ITSZ)
ITSZ:
A compressional fault line extending 3200 km from the Indus Gorge to the Tsangpo Gorge.
Represents the collision zone between the Indian Plate and the Eurasian Plate:
Rocks in this zone are crushed and pulverized.
Mostly consists of Paleozoic and ancient rocks.
Rivers:
Indus and Tsangpo flow through this reverse faulted line.
These rivers have cut through the suture zone, influencing the landscape.
Tethyan Himalayas
Tethyan Himalayas:
Average height: around 4000 m.
Characteristics:
Compressed against the Greater Himalayas.
High compressional forces due to the absence of a longitudinal valley between them.
Composition:
Submarine sedimentary and metamorphic rocks.
Represents the initial upliftment in the Tethyan Geosyncline or Murree Foredeep.
Greater Himalayas
Greater Himalayas:
Average height: around 6000 m, extending from Mt. Namcha Barwa to Nanga Parbat for 2500 km.
Features:
Considered the mightiest and most majestic mountain range.
Numerous peaks rising above 7000 m.
Characterized by high relief, deep gorges, vertical slopes, and symmetrical convexity.
Relief:
Sharp peaks and escarped valleys due to isostatic adjustment.
Composed of metamorphic and sedimentary rocks.
Core includes granitic magma (batholith).
Features asymmetrical folds and fractured rocks due to high compression.
Main Central Thrust (MCT)
Main Central Thrust (MCT):
Major tectonic thrust line along which the Greater Himalayas were uplifted.
Characteristics:
A compressional valley.
Rocks are fractured and pulverized between the Greater and Lesser Himalayas.
Examples:
Kathmandu Valley
Kashmiri Valley
Kulu Valley
Kangra Valley
Valley Types:
Kulu: Transverse valley.
Kangra and Manali: Straight valleys, more prone to earthquakes due to underlying faults.
Lesser Himalayas
Lesser Himalayas:
Average height: around 3800 m, extending about 2400 km.
Characteristics:
Runs parallel to the Greater Himalayas.
Segmented into several parallel and transverse ranges in the western section.
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