Geography Class 10
Last class revision (5:14 PM)
Earth's movement (5:30 PM)
- Various forces from the earth's interior as well as outside the earth's surface cause physical stress and chemical actions on the earth's material bringing about changes in the configuration of the surface of the earth called a geomorphic process.
- The geomorphic process results from two types of forces, endogenetic and exogenetic.
- Endogenetic forces:
- These are the forces acting from the earth's interior, the source of energy is radioactivity and primordial heat.
- They result in large-scale upliftment or subsidence or folding and faulting.
- They are responsible for the formation of major structural units of the earth's surface.
- Exogenetic forces:
- These are the forces acting on the earth's surface from above the surface.
- The sources of energy are sunlight and gravity.
- Wind, water, and glaciers are the different agents of exogenetic movements.
- These forces result in minor topographical features such as valleys and caves.
Endogentic movements (6:11 PM)
- They are classified into dystrophic and catastrophic movements.
- Catastrophic movements (Sudden movements):
- These are unpredictable movements of shorter duration.
- These movements can be observed.
- Examples are earthquakes, volcanic eruptions, etc.
- Diastrophic movements:
- Some movements move, elevate, and buildup up the portions of the earth's crust.
- These movements operate very slowly and led to the formation of primary landforms.
- They are of 3 types: tectonic, isostatic, and eustatic.
- Tectonic movement:
- The Word tectonic means to build.
- These are continent and mountain-building movements affecting the earth's surface.
- They are of 2 types Epirogenic and orogenic.
- Epirogenic movements:
- These are vertical movements caused by radial forces.
- These are characterized by large-scale upliftment/ emergency and subsidence/submergence of land areas.
- They are very slow and widespread.
- These movements led to the continental building.
- An example is the gradual upliftment of the Deccan plateau and the slow subsidence of the northern coast of the Gulf of Mexico.
- Orogenic movement:
- These are mountain-building movements caused by tangential forces.
- They involve intense folding and faulting of narrow belts.
- The tangential forces are of 2 types, Compressional resulting in folding, and tensional resulting in faulting.
- Folding:
- When the compressional forces the earth's rocks to push or squeeze against each other.
- It results in the formation of folds
- Folds are structures in which the layers are bent or distorted without the loss of continuity.
- Faulting is when tensional forces pull the rocks apart, it results in the formation of faults.
- Faults are the fractures, through which primary surfaces are broken and displaced, with the loss of continuity.
- Type of faults:
- The up-folds are called anticlines and the Downfolds are called synclines.
- A fold will have two sides called limbs.
- Symmetrical Fold:
- If the limbs of a fold are inclined at the same angle, it is called a Symmetrical fold.
- Asymmetric Fold:
- If one of the limbs is inclined more than the other, it is called an Asymmetrical fold.
- Overfold:
- It is a fold where the strata in one limb have been folded beyond the vertical axis.
- Recumbent Fold:
It is a fold lying down resulting from the continuation of pressure on one of the limbs. - Nappe:
- It is formed when the pressure exerted upon a Recumbent Fold is sufficiently great to cause it to be torn from its roots and thrust forward.
- Nappes are well-developed in the Himalayas.
- Types of Faults:
- Normal Fault:
- When one of the blocks moves downward relative to the other due to tensional forces it is called a Normal fault or Dip Slip Fault.
- Reverse Fault:
- When one block moves up about the other one due to compressional forces it is called a Reverse Fault or Thrust Fault.
- Strike-Slip Fault:
- Where both the blocks move across each other involving no vertical movements it is called Strike-slip or Transform Fault.
- In a fault, the upthrust block is called a Horst and the down-dropped block is called a Graben.
The difference between the fold and the fault mountains(8.03 PM):
Fold mountains: Fault/block mountains: It is because of the folding process. Due to the Faulting process Only compressional force Both compressional and tension force They are greater in length They are greater in width. For example Himalayas and Alps For example Vindhyas and Blackforest
The topic for the next class: Isostatic movement and Eustatic movement.
Images
Here are 40 short answer type questions with answers based
on notes on Geography Class 10:
1. What causes changes in the configuration of the earth's
surface?
- Geomorphic
processes.
2. What are the two types of forces involved in geomorphic
processes?
- Endogenetic and
exogenetic forces.
3. What are endogenetic forces?
- Forces acting
from the earth's interior, powered by radioactivity and primordial heat.
4. What do endogenetic forces result in?
- Large-scale
upliftment, subsidence, folding, and faulting.
5. What are exogenetic forces?
- Forces acting on
the earth's surface from above, such as sunlight and gravity.
6. What do exogenetic forces result in?
- Minor
topographical features like valleys and caves.
7. What are the two classifications of endogenetic
movements?
- Diastrophic and
catastrophic movements.
8. What are catastrophic movements?
- Unpredictable
movements of shorter duration, like earthquakes and volcanic eruptions.
9. What are diastrophic movements?
- Slow movements
that elevate and build up portions of the earth's crust, leading to the
formation of primary landforms.
10. What are the three types of diastrophic movements?
- Tectonic,
isostatic, and eustatic.
11. What does the term 'tectonic' mean?
- To build.
12. What are tectonic movements?
- Continent and
mountain-building movements affecting the earth's surface.
13. What are the two types of tectonic movements?
- Epirogenic and
orogenic movements.
14. What are epirogenic movements?
- Vertical
movements caused by radial forces, leading to upliftment or subsidence of land
areas.
15. What are orogenic movements?
-
Mountain-building movements caused by tangential forces, involving intense
folding and faulting.
16. What are the tangential forces in orogenic movements?
- Compressional
(resulting in folding) and tensional (resulting in faulting).
17. What is folding?
- When
compressional forces cause the earth's rocks to push or squeeze against each
other, forming folds.
18. What is faulting?
- When tensional
forces pull the rocks apart, resulting in faults.
19. What is an anticline?
- An up-fold in
rock layers.
20. What is a syncline?
- A down-fold in
rock layers.
21. What is a symmetrical fold?
- A fold where the
limbs are inclined at the same angle.
22. What is an asymmetrical fold?
- A fold where one
limb is inclined more than the other.
23. What is an overfold?
- A fold where the
strata in one limb have been folded beyond the vertical axis.
24. What is a recumbent fold?
- A fold lying
down due to continued pressure on one limb.
25. What is a nappe?
- A recumbent fold
torn from its roots and thrust forward.
26. What is a normal fault?
- A fault where
one block moves downward relative to the other due to tensional forces.
27. What is a reverse fault?
- A fault where
one block moves up relative to the other due to compressional forces.
28. What is a strike-slip fault?
- A fault where
both blocks move across each other with no vertical movement.
29. What is a horst?
- The upthrust
block in a fault.
30. What is a graben?
- The down-dropped
block in a fault.
31. What are fold mountains?
- Mountains formed
due to the folding process.
32. What are fault/block mountains?
- Mountains formed
due to the faulting process.
33. What type of force is involved in the formation of fold
mountains?
- Compressional
force.
34. What type of forces are involved in the formation of
fault mountains?
- Both
compressional and tensional forces.
35. Which mountains are greater in length: fold mountains or
fault mountains?
- Fold mountains.
36. Which mountains are greater in width: fold mountains or
fault mountains?
- Fault mountains.
37. Give an example of fold mountains.
- The Himalayas
and the Alps.
38. Give an example of fault mountains.
- The Vindhyas and
the Black Forest.
39. What is the source of energy for exogenetic forces?
- Sunlight and
gravity.
40. What are the agents of exogenetic movements?
- Wind, water, and
glaciers.
1)
Which of the following can be considered endogenic forces?
- Earthquakes
- Ground Water
- Plate Movements
- Volcanoes
Select the correct answer from the codes given below:
(a)1 only
(b)1 and 2 only
(c)1, 3 and 4 only
(d)1,2,3 and 4
2)
Consider the following statements:
- Endogenetic forces are responsible for the erosion of fold mountains of the earth
- Exogenetic forces derive their energy from the interior of the earth.
Which of the statements given above is/are correct?
(a)Only 1
(b)Only 2
(c)Both 1 and 2
(d)Neither 1 nor 2
3)
Which of the following are sources of energy for endogenetic forces?
- Gravity.
- Primordial heat.
- Radioactivity under the earth.
Choose the correct answer using the codes given below:
(a)1 and 2 only
(b)1 and 3 only
(c)2 and 3 only
(d)All of the above
4)
Consider the following statements with respect to the types of Folds
- The overturned fold is one in which one limb of the fold is thrust upon another fold due to intense tensional forces.
- Nappes are formed due to an increase in the continued compressive force one limb of the recumbent fold slides forward and overrides the other fold.
Which of the above statement(s) is/are correct?
(a)1 only
(b)2 only
(c)Both 1 and 2
(d)Neither 1 nor 2
5)
Consider the following statements with respect to faults
- Normal faults occur due to the compressional forces and result in the movement of one block in an upward direction with respect to the other block.
- A reverse fault occurs due to the tensional forces and results in the movement of one block in a downward direction with respect to the other block.
- In a transform fault, both the blocks move across each other involving no vertical movement with only lateral movement.
Which of the above statements is/are correct?
(a)1 and 2 only
(b)3 only
(c)1 and 3 only
(d)2 an 3 only
6)
With reference to the difference between fold and fault, consider the following statements:
- The folds are formed when the dominant force is compressive force whereas faults can occur either due to tensional or compressional forces.
- The up-folded and down-folded rock strata are known as anticlines and synclines whereas the trough-like depression in a fault is called Graben and the upthrown block is called Horst.
- Upwarping and downwarping are the features that occur in folds whereas cracks, fractures, and ruptures are the features of faults.
Which of the following statements is/are correct?
(a)1 only
(b)2 and 3 only
(c)1 and 3 only
(d)All of the above
7)
"It is also called Transform Fault, where both the blocks move across each other involving no vertical movements." Which of the following best describes this type of fault?
(a)Normal Fault
(b)Reverse Fault
(c)Strike-Slip Fault
(d)None of the Above
8)
Which of the following fault is aslo called " Dip Slip Fault"?
(a)Reverse Fault.
(b)Normal Fault.
(c)Strike-Slip Fault.
(d)None of the above.
9)
What do you understand by the "tectonic movements"? Also, discuss about the epeirogenic and orogenic movements with suitable examples. (150 words)
10)
Mention the different type of faults and folds in detail?(150 words/10 marks)
Answers
1) c
2) d
3) c
4) b
5) b
6) d
7) c
8) b
Define Geomorphic processes and discuss the types of forces inducing them.(150 words/10 marks)
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