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Class VII T1 SS G U1 INTERIOR OF THE EARTH TEXTBOOK SOLUTIONS
UNIT -1
INTERIOR OF THE EARTH
Evaluation
I. Choose the correct answer
1. Nife is made up of ___________ .
a) Nickel and ferrous
b) Silica and aluminum
c) Silica and magnesium
d) Iron and magnesium
Ans: a) Nickel and ferrous
2. Earthquake and volcanic eruption occur near the edges of ______________.
a) Mountain b) Plains c) Plates d) Plateaus
Ans: a) Mountain
3. The magnitude of an earthquake is measured by ______________.
a) Seismograph b) Richter scale c) Ammeter d) Rotameter
Ans: b) Richter scale
4. The narrow pipe through which magma flows out is called a ______________.
a) Vent b) Crater c) Focus d) Caldera
Ans: a) Vent
5. _____________ Volcano is known as light house of Mediterranean Sea.
a) Stramboli b) Krakota c) Fujiyama d) Kilimanjaro
Ans: a) Stramboli
6. __________ belt is known as the “Ring of Fire”.
a) Circum - Pacific b) Mid-Atlantic c) Mid - Continental d) Antarctic
Ans: a) Circum - Pacific
II. Fill in the blanks
1.The core is separated from the mantle by a boundary called ______________.
Ans: Weichart-Gutenberg discontinuity
2. The earthquake waves are recorded by an instrument known as __________.
Ans: Seismograph
3. Magma rises to the surface and spreads over a vast area is known as ________.
Ans: fissure eruption.
4. An example for active volcano is ______________.
Ans: Mauna Loa in Hawaii
5. Seismology is the study of __________.
Ans: earthquake
III. Circle the odd one
1. crust, magma, core, mantle
Ans: magma
2. focus, epicenter, vent, seismic waves
Ans: vent
3. Uttar Kashi, Chamoli, Koyna, Krakatoa
Ans: Krakatoa
4. lava, caldera, silica, crater
Ans: Silica
5. Stramboli, Helens, Hawaii, Fujiyama
Ans: Fujiyama
IV. Match the following
1.Earth quake - Sudden movement
2. Sima - Silica and magnesium
3. Pacific Ring of Fire- World volcanoes
4. Tsunami - Japanese term
5. Mt. Kenya - Africa
V. Consider the following statement and ( ) Tick the appropriate answer
1. Assertion (A): The structure of the earth may be compared to that of anApple.
Reason (R): The interior of the earth consists of crust, mantle and core.
a) A and R are correct and R explains A
b) A and R are correct but R does not explain A
c) A is incorrect but R is correct
d) Both A and R are incorrect
Ans: a) A and R are correct and R explains A
2. Assertion (A): The Pacific Ocean includes two thirds of the world’s volcanoes.
Reason (R): The boundary along the Eastern and Western coast areas of the Pacific Ocean is known as the Pacific Ring of Fire.
a) A and R are correct and R explains A
b) A and R are correct but R does not explain A
c) A is incorrect but R is correct
d) Both A and R are incorrect
Ans: b) A and R are correct but R does not explain A
VI. Answer in a word
1. Name the outermost layer of the earth.
Crust.
2. What is SIAL?
SIAL is a mixture of Silica and Aluminium.
3. Name the movement of the Earth’s lithospheric plates?
Tectonic movements.
4. Give an example of extinct volcano.
Mt. Kenya of Africa
VII. Answer the following briefly
1. What is mantle?
The layer beneath the crust is called mantle.The mantle is about 2,900 km thick.It is divided into two parts,upper and lower mantle.
2. Write note on the core of the earth?
The innermost layer of the earth is called the core. It is also known as barysphere. It is separated from the mantle by a boundary called Weichart-Gutenberg discontinuity. The core is also divided into two parts, outer core and inner core.
3. Define Earthquake.
A sudden movement of a portion of the earth’s crust which produces a shaking or trembling is known as an earthquake.
4. What is Seismograph?
An instrument used to measure earthquake waves is known as seismograph.
5. What is a volcano?
A volcano is a vent or an opening in the earth’s crust through which hot magma erupts from deep below the surface. The opening is usually circular in form.
6. Name the three types of volcanoes based on periodicity of eruption.
Volcanoes are classified according to their periodicity of eruptions and the state of activity such as
1. Active Valcano
2. Dormant Valcano
3. Extinct Valcano
VIII. Give reason
1. No one has been able to take samples from the interior of the earth.
The earth’s crust density is high and it has very high temperature and pressure. So, it is not possible to take samples from the interior of the earth.
2. The Continental crust is less dense than the oceanic crust
The continental crust has a density of about 2.6 g/cm3 which helps the continents of the world to stay in one place.
The oceanic crust has a density of around 3.0 g/cm3.
The oceanic crust is made up of dark basalt rocks that are rich in minerals and substances like silicon and magnesium.
The continental crust is made up of light-colored granite rocks full of substances like oxygen and silicon.
IX. Distinguish between
1. SIAL and SIMA
2. Active volcano and dormant volcano
X. Answer the following in detail
1. Write about the effects of an earthquake?
☸Earthquakes may cause changes in the earth’s surface.
☸Vibrations often set landslides in mountainous regions.
☸A greater danger in an earthquake is the falling of buildings.
☸Most of the houses which collapsed were made of mud and bricks and proved to be death traps.
☸Underground water system is naturally disturbed by such movements.
☸Fire is another great danger.
☸An earthquake which originates below or near the sea causes great disturbance in the water.
☸Tsunami, a Japanese term, is the name given to the huge waves caused in the sea by an earthquake.
2. Describe the classification of volcanoes based on the eruptions.
A volcano is a vent or an opening in the earth’s crust through which hot magma erupts from deep below the surface.
Volcanoes are classified according to their periodicity of eruptions and the state of activity such as
1. Active Valcano
2. Dormant Valcano
3. Extinct Valcano
1. Active Valcano
Valcanoes that erupt frequently are called active volcanoes. Most of the active volcanoes lie in the Pacific Ring of Fire belt which lies along the Pacific coast.
eg.Mt. Stromboli in Mediterranean Sea, St.Helens in USA, Pinatubo in Philippines. Mauna Loa in Hawaii.
2. Dormant Valcano
These volcanoes have shown no sign of activity for many years but they may become active at any time. These are called Sleeping Volcanoes.
eg.Vesuvius mountain of Italy, Mt Fujiyama of Japan, Mt. Krakatoa of Indonesia
3. Extinct volcano
A Volcano that has not erupted in the past 1000 years is often listed as Extinct volcanoes. The top of extinct volcanic mountains have been eroded.
eg.Mt Popa of Myanmar and Mt. Kilimanjaro and Mt. Kenya of Africa.
3. Name the major zones of volcanic activity and explain any one.
Volcanoes are located in a clearly-defined pattern around the world. The volcanic belts are also the principal earthquake belts of the world.
There are three major zones of volcanic activities in the world. They are:
1. The Circum – Pacific belt
2. The Mid continental belt
3. The Mid Atlantic belt
Mid Atlantic Belt:
The Mid Atlantic belt represents the divergent boundary of plates located along the midAtlantic ridges. Volcanoes of this area are mainly of fissure eruption type. Iceland is the most active volcanic area and is located on the mid-Atlantic ridge. St. Helena and Azores Island are other examples.
XI. HOTs
1. The earth’s interior is very hot. Why?
The interior of Earth is very hot and the temperature of the core reaches more than 5,000 degrees Celsius, this is because of
☸The heat from when the planet formed and accreted
☸The heat from the decay of radioactive elements.
2. Are Volcanoes Destructive (or) Constructive?
According to scientists, volcanoes are known as “constructive” forces. That is, volcanoes often result in the construction of new landforms. “Destructive” forces are those like erosion or weathering in which landforms are broken down into smaller pieces like soil and sand.
3. How does volcanoes make an Island?
When volcanoes erupt, they build up layers of lava that eventually break the water’s surface. When the tops of the volcanoes appear above the water, an island is formed. While the volcano is still beneath the ocean surface, it is called a seamount.
