Chapter 1 Earth Movements Solutions

A

B

C

(1) Widespread volcanic eruption

(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) Philippines

(5) Circum Pacific belt

(5) Mayon

(6) Volcanic material

(6) Volcanic bombs

(6) Solid

2. Identify the correct correlation.

A : Assertion R : Reasoning
Question 1.
A – Faulting leads to development of fold mountains.
R – Faulting occurs when tensional forces move away from each other.
(a) Only A is correct.
(b) Only R is correct.
(c) Both A and R are correct and R is the correct explanation of A.
(d) Both A and R are correct but R is not the correct explanation of A.
Answer:
(b) Only R is correct.

3. Identify the correct group.

A

B

C

D

(1) Symmetrical Fold

(1) Black Forest

(1) Narmada Valley

(1) Caldera

(2) Isoclinal Fold

(2) Vosges

(2) African Valley

(2) Crater Lake

(3) Overturned Fold

(3) Himalayas

(3) Tapi Valley

(3) Cinder Cone

(4) Recumbent Fault

(4) Satpuras

(4) Rhine Valley

(4) Lava Plateau

5. Answer in detail.

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.

Tear fault: At times, the rock strata on either side of the fault plane do not have vertical displacement. Instead, movement occurs along the plane in horizontal direction.

Thrust fault: When the portion of the land on one side of the fault plane gets detached and moves over the land on the other side. The angle of fault plane is generally less than 45°.

Lava plateaus:

Caldera:

Crater lake:
When the funnel shaped crater of an extinct volcano gets filled with rain water, it forms a crater lake.

Volcanic plug:

Cinder cone:

Composite cone:

Solid material:

Gaseous material:

6. Differentiate between.

7. Draw a neat and labelled diagram.

11th Geography Digest Chapter 1 Earth Movements Intext Questions and Answers

Let’s recall (Textbook Page No. 1)

1. Observe the following pictures in fig 1.1 and discuss the questions.

2. On 19th August, 2018, around 300 people died in Indonesia. Many buildings collapsed. Many roads broke apart. A tsunami was generated. (Textbook Page No. 6)

Think about it.

Try this.

Can you tell? (Textbook Page No. 7)

In fig 1.10 textbook page 6 A, B, C are three points on the earth’s surface. Analyse their location with respect to epicentre and shadow zones
Answer:
A, B, C are the points on the surface of the earth.
(i) ‘A’ point is located with 105° from the epicentre, therefore P waves and S waves reach at ‘A’ point. The seismograph at !A’ point records both waves, therefore ‘A’ point is not in shadow zone.

(ii) ‘B’ point is in shadow zone because both the waves do not reach there. P waves pass through all mediums, they experience refraction as they pass on one medium to another. The seismograph records P waves, which is located away from ‘B’ point. But P waves are not recorded in an area between 105 and 140° from epicentre. The S waves also do not reach here. Therefore, it is called ‘Shadow zone’ of Earthquake waves.

(iii) ‘C’ point is in the area of the shadow zone of ‘S’ waves, that in within 140°. P waves reach beyond 140°. Since ‘S’ waves do not reach here, it is called ‘Shadow zone of S waves’.

Read the following passage about Krakatoa volcanic eruption and answer the following questions. (Textbook Page No. 10)

There is an island known as Krakatoa between the islands of Java and Su matra in Indonesia. There were frequent volcanic eruptions here. From May 1883, massive explosions began. The eruption that took place at about 10 in the morning on 28 August 1883 was the largest ever recorded explosion. As a result of this explosion, the entire island disappeared. During this eruption, rock particles and dust thrown up in the atmosphere was about 25 km³. The column of this dust-ash rose as high as 80 km.

The discharge of Krakatoa threw into the air nearly 21 km3 of rock fragments, and large quantities of ash fell over an area of some 800,000 km². Near the volcano, masses of floating pumice, were so thick that ships had to halt. The surrounding region was plunged into darkness for two and a half days because of ash in the air. For some years after this, cloud kept moving round the earth. About 36,000 people died in these eruptions and the tsunami waves created by it.

In 1927, volcanic eruptions began at the same place and a new island rose in place of the Krakatoa island that had vanished. It was named Anak Krakatoa’ or ‘Child Krakatoa’. The volcano here constantly emits ash and steam. This new island has now become a laboratory for geologists and biologists.

Find out! (Textbook Page No. 9)

Find out examples of active, dormant and extinct volcanoes.
Answer:
Examples of active volcanoes are – Mt. Etna (Italy), Stromboli (Italy), Mt. Merapi (Indonesia), Erta Ale (Ethiopia), Mt. Erebus (Antarctica)
Examples of dormant volcanoes – Mt. Kilimanjaro (Africa), Mt. Katmai (Alaska)
Examples of extinct volcanoes – Mt. Egmont (New Zealand), Chimborazo (Ecuador), Mt. Kulal (Kenya)

Give it a try (Textbook Page No. 8)

Take the given hypothetical data in the table. The data shows the time of arrival of P-waves and S-waves at 3 seismograph stations. Assume the scale of the map as 1 cm : 18 km. See fig. 1.11.

Answer:
Speed of waves = 08 kms per second
Scale of the map = 1 cm
= 18 kms
First step : Find out the difference in time for waves at Jalana recording centre.
Difference in time of waves = Time of S-wave – Time of P-wave
11 : 06 : 19 (Time of S-wave)
11 : 06 : 06 (Time of P-wave)
= (Time of S-wave) – (Time of P-wave)
= 11 : 06 : 19 – 11 : 06 : 06
= 00 : 00 : 13
Therefore difference in time for waves at Jalana recording centre is 13 seconds.

Second Step : Find out distance on land between Jalana and Epicentre
Distance on land = Difference in time of waves × speed of waves per second
= 13 × 8
= 104
Therefore distance on land between Jalana and Epicentre is 104 km.

Third Step : Find out radius for Jalana Station.
Jalana – Radius of circle =
=
= 5.7 cm.
Therefore radius of circle around Jalana station is 5.7 cm.
Now find out radium for remaing stations.
Jalana – 5.7 cm, Washim – 7.5 cm, Aurangabad – 8 cm.

Fouth step : Now draw circles around Jalana, Washim and Aurangad with the help of radius calculated.
All arcs of circle will intersect one another at a particular point. That point is the location of Epicentre.
In the map given below Epicentre is to the south of Mudgal.