Geomorphology 15 - Class Notes PDF

# UPSC ## Batch: SANKALP 2026 ### Geomorphology #### Subject:- Geography #### Lecture No.-15 By- Himanshu Thapa Sir # Topics to be covered ## Endogenetic & Exogenetic Forces (Part 03) # Topic: Endogenetic Forces - Rising Magma - "Sudden Force" - Very Fast Moving Forces - Earthquakes - V...

# UPSC ## Batch: SANKALP 2026 ### Geomorphology #### Subject:- Geography #### Lecture No.-15 By- Himanshu Thapa Sir # Topics to be covered ## Endogenetic & Exogenetic Forces (Part 03) # Topic: Endogenetic Forces - Rising Magma - "Sudden Force" - Very Fast Moving Forces - Earthquakes - Volcanic Eruptions - Also known as Catastrophic Forces - Diastrophic Movement/Forces - Very Slow Movements - **Epeirogenetic Forces** - These are vertical in nature. - Upward Movement - Downward Movement - Continent building Forces - Upliftment or subsidence of land - Mt. Building Forces - **Orogenic Forces** - These are horizontal in nature - Compressional Force - Tensional Force # Topic: Epeirogenic Forces - **(1) Upward Movement** - There are two conditions: - **(a) Upliftment:** When the already existing land is being pushed upward, then it is known as UPLIFTMENT. - **Example:** Ozark Plateau of USA - **(b) Emergence:** The submerged part of the Earth's crust is being pushed upwards to such an extent that it rises about the sea level. - **Example:** Eastern Coast of India - **(ii) Downward Movement** - There are two conditions: - **(a) Subsidence of Land:** A part/portion of already existing land gets subsided. - **(b) Submergence:** A part of land gets submerged under seawater due to vertical downward movement. - **Example:** Atoll Islands # Topic: Orogenic Forces - **ORO** means Mountains - **(i) "COMPRESSIONAL" FORCES:** These are horizontal forces acting towards each other. - **"South African (O)" WARP"** - These are upward bends found on the Earth’s crust due to moderate compressive forces. - The slope of the warp is very less (generally < 5’) - These are extensive in nature. - **(ii) "FOLD":** Wave like bends in the crustal rocks due to horizontal forces: - **Sedimentary Rocks:** If the compression is very high, then these rocks will be uplifted and folded to form a Mountain Range. - **Anticline:** - **Crest of a Fold:** Peaks of a fold Mt. Uplifted sedimentary parts - **Syncline:** - **Trough of a Fold** Depressed part of a fold. These forms Valleys - **Anticlinorium:** - It is called Anticlinorium. - Middle Himalayas of India, or Nepal - **Synclinorium:** - A syncline with anticlines and synclines is known as Synclinorium. - In case of extreme compressive forces, the anticlinal region breaks and gets crushed. These crushed particles again get folded to form anticline and syncline in the Anticlinal Region. # Topic: Types of Folds - **(1) Symmetrical Fold:** - Both the limbs are equal in size. - The angle formed by both the limbs is equal. - Compressive forces are equal. - **Example:** Jura Mts of Switzerland - **(2) Asymmetrical Fold:** - The limbs are of different sizes. One limb is larger. - The angle formed by limbs on the axis is not equal. - Compressive forces from the both sides are not equal. - **Example:** Pennine Mts of Great Britain - **(3) Monoclinal Fold:** - One limb is perpendicular to the Earth's surface and is shorter in length. - It is a result of more compression from one end. - **Example:** Great dividing range of Australia - **(4) Isoclinal Folds:** Result of continuous horizontal compressive force. - The limbs tilted towards the Earth's surface. - Both the limbs become parallel to each other. - These folds are very common in Middle Himalayas of Uttarakhand and HP - **(5) Recumbent Folds:** - Compressive forces from both ends are unequal. - Both the limbs become horizontal to the Earth’s surface. - Both the limbs are parallel to each other. - Result of extreme compressive forces. - **Example:** Garhwal & Kumaon Himalayas - **(6) “Overturned Fold”:** - This is a result of “cont” extreme compressive forces. - It is an example of unequal force. - The upper horizontal limb of recumbent fold overturns. - These are uncommon folds, however, these overturned folds can be seen in the Middle Himalayas. - **Example:** - Nanga Parbat - Pir Panjal Range in J&K - Dhauladhar Range in HP - Mussorie Range - UK - Nagtibba - UR + Nepal - Mahabharata Range - Nepal - Darjeeling - WB, Range # Topic: NAPPE - Due to extreme comp. force, the limb of overturned fold breaks. It moves along with the direction of compressive force. - Breaking point: 2 kms - 5 kms - After traveling for 2kms - 5kms., it stops and get placed over another structure. This new formed unique structure is known as “NAPPE” (Kashmir Himalayas, Garhwal). # Topic: - The broken limb of the fold overrides the rock beds and gets placed on some other rock structure. - This type of structure is known as “NAPPE”. # Topic: - Image of a mountain range with a river flowing through it. The left side of the image is an arrow pointing towards a bend in the river. On the right side of the image, there are two arrows pointing towards the direction of the river flow. # Thank You