Maharashtra Board Class 11 Geography Solution Chapter 1 Earth Movements
Balbharati Maharashtra Board Class 11 Geography Solution Chapter 1: Earth Movements. Marathi or English Medium Students of Class 11 get here Earth Movements full Exercise Solution.
Std |
Maharashtra Class 11 |
Subject |
Geography |
Chapter |
1 |
Chapter Name |
Earth Movements |
1) Complete the chain :
A | B | C |
1)Widespread Volcanic Eruptions | 1) Zone V | 1) I to XII |
2) Andaman and Nicobar Islands | 2) Fissure eruption | 2) Block Mountain |
3) Mercalli scale | 3) Intensity | 3) Very high seismic vulnerability |
4) Slow movements | 4) Faulting | 4) Solid |
5) Phillippines | 5) Volcanic bombs | 5) Deccan Trap |
6) Volcanic material | 6) Circum Pacific belt | 6) Mayon |
Answer : – The completed chain is as follows : –
A | B | C |
1)Widespread Volcanic Eruptions | 1) Fissure eruption | 1) Deccan Trap |
2) Andaman and Nicobar Islands | 2) Zone V | 2) Very high seismic vulnerability |
3) Mercalli scale | 3) Intensity | 3) I to XII |
4) Slow movements | 4) Faulting | 4) Block Mountain |
5) Phillippines | 5) Circum Pacific belt | 5) Mayon |
6) Volcanic material | 6) Volcanic bombs | 6) Solid |
2) Identify the correct correlation :
A : Assertion; R : Reasoning
1) A : Faulting leads to development of fold mountains.
R : Faulting occurs when tensional forces move away from each other.
1) Only A is correct
2) Only R is correct
3) Both A and R are correct and R is the correct explanation of A.
4) Both A and R are correct but R is not the correct explanation of A.
Answer – 2) Only R is correct
2) A : Intensity of an earthquake is a measurement of the energy released during an earthquake.
R : Mercallis scale is used to measure intensity of an earthquake.
1) Only A is correct
2) Only R is correct
3) Both A and R are correct and R is the correct explanation of A.
4) Both A and R are correct but R is not the correct explanation of A.
Answer – 3) Both A and R are correct and R is the correct explanation of A.
3) A : South-East Asia, Japan and islands in the Pacific Ocean are most vulnerable to
earthquakes and volcanic eruption.
R : They are located in ‘Ring of Fire’.
1) Only A is correct
2) Only R is correct
3) Both A and R are correct and R is the correct explanation of A.
4) Both A and R are correct but R is not the correct explanation of A.
Answer – 3) Both A and R are correct and R is the correct explanation of A.
3) Identify the correct group :
A) 1) Symmetrical fold B) 1) Black Forest
2) Isoclinal fold 2) Vosges
3) Overturned fold 3) Himalayas
4) Recumbent fault 4) Satpuras
C) 1) Narmada Valley D) 1) Caldera
2) African Valley 2) Crater lake
3) Tapi Valley 3) Cinder Cone
4) Rhine Valley 4) Lava plateau
Answer – The correct group is
D) 1) Caldera
2) Crater lake
3) Cinder Cone
4) Lava plateau
4) Give geographical reasons :
1) Extinct conical volcanoes often form crater lakes.
Answer – Extinct volcanoes show no volcanic activity for several thousands of years and after the eruption, a large and deep depression remains in that area which is called caldera. These can be around 10 km wide and hundreds of metres deep and may later turn into lakes due to inactivity of the volcano over thousands of years. Smaller calderas thus formed are known as craters.
When these funnel shaped crater of an extinct volcano is filled with rain water, ground water circulation or ice, it forms a crater lake.
2) People living in the Himalayas are more vulnerable to earthquakes.
Answer – Tectonic movements : The earth’s crust consists of several large and small unstable tectonic plates. They float on denser portion of the upper mantle zone. Due to their movements, the earthquake generally occurs along their margins (divergent and convergent).
The Himalayas are formed due to the tectonic collision of the Indian tectonic plate and the Eurasian plate and their sudden movements are the main reason rendering the region vulnerable to earthquakes.
According to the tectonic plate theory, the Inda-Australian plate is moving towards the north and is slowly moving under the Eurasian plate, causing friction between the two plates.
These reasons are the main causes of the Himalayan region being more vulnerable to earthquakes.
3) L-waves do not have a shadow zone.
Answer – The shadow zone is the area of the earth at an angular distance between 105 degree to 140 degrees from a given earthquake for both P-waves and S-waves.
Seismographs located at any point within 105degrees from the epicentre record S-waves, and beyond 140degrees record P-waves.
However, L-waves are generated when the source of the earthquake is closer to the earth’s surface.
The l-waves are generated when the epicentre of the earthquake (or its source) occurs relatively closer to the surface of the earth and hence this kind of wave does not have a shadow zone.
4) Soft rocks form folds while hard rocks form faults.
Answer – Folding occurs when compressional forces are applied to rocks that are ductile or flexible ie soft rocks. Within the earth’s crust, the rocks that lie deep inside are usually under high pressure. They are usually ductile and therefore tend to form folding, instead of breaking. Folding occurs when compressional forces are applied slowly.
On the other hand, rock layers that are near the Earth’s surface and not under high confining pressures are too rigid to bend into folds ie hard rocks. If the tectonic force is large enough, these rocks will break rather than bend. Such breaks may also be called fractures, ruptures or faults.
5) Folds depend on the strength of rocks and intensity of forces.
Answer – Compressional forces push two portions of crustal rocks together and tend to shorten and thicken the crust. The affected rocks react to compressional forces depending on the strength of the rocks and the speed or intensity of the forces. Folding occurs when compressional forces are applied to rocks that are ductile or flexible. Rocks that lie deep within the crust and are therefore under high pressure are generally ductile and particularly susceptible to folding without breaking. As a result rocks deep within the crust typically fold rather than break. Folding is also likely to occur where compressional forces are applied slowly.
5) Answer in detail :
1) Explain different types of faults.
Answer – Faulting – In the earth’s crust, the forces operating in opposite direction lead to stress or tension causing faulting. Rocks therefore develop cracks or fissures. In these regions where cracks are developed rocks get displaced and such displacement can occur in the upward, downward or horizontal directions. Faulting can be classified according to the displacement in rocks. Rock layers that are nearer to the Earth’s surface that are not under high confining pressures are too rigid to bend into folds. Further if the tectonic force is large enough, these rocks will break rather than bend. Such breaks may also be called fractures, ruptures or faults. Also the rock masses will move relative to each other along the fracture i.e. the zone where they break. One part of the rock strata moves along the plane of fracture upwards or downward relative to the other parts. The plane of fracture is called fault and often results in the formation of block mountains and rift valleys.
Types of faults :
A) Normal fault : Normal faults results when a portion of land slides down along the fault plane and when the exposed portion of the plane faces the sky.
B) Reverse fault : It results when a portion of the land is thrown upward relative to other side of the land. In such situation, the fault plane faces the ground.
C) Tear fault : At times, the rock strata on either sides of the fault plane do not have vertical displacement. Instead movement occurs along the plane in horizontal direction.
D) Thrust fault : When the portion of the land on one side of the fault plane gets detached and moves over land on the other side. The angle of fault plane is generally low less than 45°.
2) Explain with examples, different types of landforms produced by volcanic eruption.
Answer – Quite a number of landforms are formed due to cooling and solidification of magma. Some such important landforms are given below.
1) Lava Domes : Domes are developed when magma comes out and solidifies around its mouth. The shape of such domes depend upon fluidity of lava. High dome with steep slopes are developed by acidic lava. Due to basic lava, broad-based low domes are developed.
2) Lava Plateaus : Due to spread of lava in huge quantity from fissure volcano, it covers large areas and plateaus are formed. The Deccan Trap in India has developed from volcanic eruptions millions of years ago.
3) Caldera : At times, the eruption of a volcano brings about large quantity of material and
relieves lot of pressure. After the eruption, a large and deep depression remains in that area. This large depression is called caldera. These can be around 10 km wide and hundreds of metres deep. They may later turn into lakes. Smaller calderas are known as craters.
4) Crater lake : When the funnel shaped crater of an extinct volcano is filled with rain water, its forms a crater lake.
5) Volcanic plug : It is formed, when the lava solidifies in the volcanic neck.
3) Explain the concept of shadow zone.
Answer The waves that are caused by the earthquakes are called seismic waves, which are mainly of three types: P-waves, S-waves and longitudinal waves. The P-waves pass through all mediums while S-waves pass only through solid medium. P-waves even though they pass through all mediums, they experience a refraction while passing from one medium to another. Earthquake waves get recorded in instruments called seismographs usually located at locations far off from the epicentre. There however, exists some specific areas where the waves of that earthquake are not reported. Such a zone is called the ‘shadow zone’, as the name signifies, lack of waves.
For each earthquake, there exists an altogether different shadow zone. It has been observed that generally, seismographs located at any distance within 105° from the epicentre, record the arrival of both P-waves and S-waves while, the seismographs located beyond 140° from the epicentre; record the arrival of P-waves, but not that of S-waves. Thus, a zone between 105° and 140° from the epicentre is identified as the shadow zone for both the types of waves. The entire zone beyond 105° does not receive S-waves. The shadow zone of P-waves appears as a band around the earth between 105° and 140° away from the epicentre. The shadow zone of S-waves is larger in extent.
Isoseismal line is an imaginary line, drawn on the map, connecting the places of uniform intensity of earthquake.
4) Write a note on volcanic materials.
Answer – Mainly three types of material come out in volcanic eruptions, namely, liquid, solid and gaseous forms.
1) Liquid material : It is the molten rock material. When the molten rock material is below the earth surface it is called ‘magma’. When it appears on the surface it is called ‘lava’. On the basis of percentage of silica it is classified into two types
a) Acidic Lava : It contains higher percentage of silica. It has got high melting point. It is thick, fluid and moves slowly.
b) Basic Lava : It contains less percentage of silica. It has low melting point. Its more fluid and can flow over longer distances.
2) Solid material : It consists of dust particles and rock fragments. When the material is very fine it is called volcanic dust. The small sized solid particles are called ash. The solid angular fragments are known as breccias. Sometime, the lava material thrown into the air solidifies into small fragments before falling on the earth surface; it is called volcanic bombs.
3) Gaseous Material : At the time of volcanic eruption, a dark cloud of smoke can be seen over the crater. On the basis of shape, cloud is called cauliflower cloud. Various inflammable gases are found in these clouds. These gases produce flames.
6) Differentiate between :
1) Folding and faulting
Answer – The differences between Folding and Faulting is as follows : –
Folding – Folding is due to bends in rock layers due to compressional forces. Mainly the soft rocks which are ductile and flexible are folded and affected by these compressional forces.
The rocks that lie deep in the earth’s crust are susceptible to folding without breaking.
Folding results in formation of fold mountains like Himalayas, Alps, etc
Faulting – Faults are formed when due to tensional forces along which displacement of rocks take place. When force operating in opposite direction leads to tension, faults occur and as a results rocks develop cracks or fissures.
Rock layers that are near the earth’s surface and not under too high pressure, and also they are rigid and harder to bend forms cracks, and fissures, therefore are susceptible to faulting.
Faulting results in formation of block mountains like black forest mountains etc. right valleys like Narmada, Tapi etc.
2) Normal fault and Reverse fault
Answer – Difference between Normal and Reverse faults is as follows : –
Normal fault results when a portion of land slides down along the fault plane.
Also, the exposed portion of the plane faces the sky.
Reverse fault : Reverse faults form when a portion of the land is thrown upward relative to other side of the land.
The fault plane faces the ground.
3) Syncline and Anticline
Answer – Syncline and Anticline can be differentiated as follows : –
Folds develop in earth’s crust and both sides of a fold are called limbs. The axial plane divides a fold into two parts.
The axis may be vertical, inclined or horizontal. When limbs slope downward with central portion getting raised up, it is called anticline.
However, if limbs slope towards each other and the central part located at lower elevation, it is called synclines.
4) Asymmetrical fold and Symmetrical fold
Answer – The differences between Asymmetrical and Symmetrical folds are as follows :
Asymmetrical fold – The axial plane is inclined and the limbs are at different angles
Heights and shapes of the limbs is not the same and may differ abruptly, therefore no symmetry in them.
Symmetrical fold – The axial plane is vertical and the limbs are at same angles.
Heights and shapes of the limbs are same, thereby forming a symmetry.
5) Mercalli scale and Richter scale
Answer – Both the Mercalli and Richter scales are used for measurement of earthquake . The differences between the two can be summarised as follows :
Mercalli scale describes the intensity of an earthquake based on its observed effects, while the Richter scale describes the earthquake’s magnitude by measuring the seismic waves that are generated by the earthquake.
The two scales have different applications and measurement techniques. The energy released in an earthquake of a magnitude 5 is 32 times more than that of magnitude 4.
Earthquake Measurement – Scale | Mercalli Scale | Richter Scale |
Nature of Measurement | Measures the intensity of earthquake | Measures the energy released during an earthquake |
Measuring Tool
|
It is based on mere Observation | Measured by an instrument called Seismograph |
Quantification | Quantified from observation of
the effects on earth’s surface, humans, infrastructures , objects and man-made structures |
Quantified on a Logarithmic scale obtained by calculating logarithm of the amplitude of waves. |
Unit | I (not felt at all ) to XII (total destruction) | From < 2.0 to 10.0+ (never
recorded). 3.0 earthquake releases 32 times more energy than a 2.0 earthquake. |
6) Slow movements and sudden movements
Answer – Differences between Slow movement and sudden movement is as follows : –
Slow movement – Movements that are both horizontal and vertical in nature, caused due to forces deep within the earth’s crust.
Slow movement include movements that result in formation of mountains and continents and are occurring continuously.
Sudden movements – Sudden movements are caused by sudden endogenic forces coming from deep within the earth. They are the reason for volcanoes and earthquake. They are not continuous but abrupt, sudden and catastrophic, therefore results in an event.
7) Draw diagrams for :
1) Types of folds
2) Types of faults
3) Shadow zone
4) Volcanic landforms