Geography of Uttarakhand | Uttarakhand State PSC (UKPSC): Preparation - UKPSC (Uttarakhand) PDF Download

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Geography
 
of
 
Uttarakhand
In Himalayas, we have three major faults which are thrust faults. Thrusts
result from crustal shortening (decrease in area of crust), in our case this is
due to the collision of the Indian plate with the Eurasian plate
Main Central Thrust (MCT)- The Main Central Thrust, marking the
boundary between the Lesser and Higher Himalayas, is a zone of more or
less parallel thrust planes along which the rocks of the Central Crystallines
have moved southwards against, and over the younger sedimentary and
metasedimentary (Paleozoic?) rocks. It is a major tectonic feature, well
defined, and easily recognisable in general.
Main Boundary Fault (MBT)- Separating the Siwalik Formations of the
Sub-Himalayas from the older rocks lying to their north, the Main
Boundary Fault is a major structural plane discernible throughout the
length of the Himalayas. Hitherto regarded as a steep north dipping fault,
it is more likely a thrust which flattens with depth. The MBF, originally
defined as the tectonic feature separating the Siwalik from the pre Siwalik
Tertiaries, is exposed only in the extreme western sector in the Kumaon
Himalayas, roughly between the Yamuna and Tons valleys. The older
rocks of the Lesser Himalayas are thrust over the Siwaliks along a series
of more or less parallel thrust planes. The Main Boundary Fault is a thrust
fault with large-scale movements and is still very active.
Himalayan Frontal Fault- Separates Shivaliks from the plain especially
Bhabar Region. It is youngest fault and forms frontal zone of Himalaya.
Still very active shortening of earth surface is still continuous here. crustal
shortening is dominant along this fault. In simple words, it defines the
southern boundary of Himalayas, to the south of MFT one may hardly
find any uplifted area (hills) except in few areas which are experiencing
the most recent upliftment activity. This forms tectonic boundary between
the Indian plate and the Himalayan orogenic prism.