Class 7 Geo.Ch.3 Earth's Movements and Major Landforms

Here are the correct options marked with a tick (√):

a. The Theory of Continental Drift was suggested by Professor Alfred Wegener in the year:

(i) 1812

(ii) 1912 √

(iii) 1911

b. The place of origin of an earthquake below the surface of the Earth is known as:

(i) focus √

(ii) epicentre

(iii) vent

c. When _____ volcanoes erupt, they often do so very violently.

(i) dormant

(ii) active √

(iii) extinct

d. The sudden movements which originate from within the Earth can cause

(i) volcanic eruption √

(ii) folding

(iii) faulting

e. A volcano likely to be active in the future is:

(i) extinct volcano

(ii) active volcano

(iii) dormant volcano √

  1. Here are the filled-in blanks:

a. The top of the volcano has a cup-shaped or a funnel-shaped depression which is known as a crater.

b. Folding and faulting are responsible for the formation of mountains.

c. The intensity of an earthquake is measured on a Richter scale.

d. Dormant volcanoes are those that have not erupted in the known historical times.

e. The forces which act in the interior of the Earth are called endogenic forces.

  1. Here are the statements marked as true or false:

a. The Theory of Continental Drift describes the large-scale motion of the lithosphere. False (It describes the movement of continents over the Earth's surface, while the theory of plate tectonics describes the motion of the lithosphere.)

b. The place of origin of an earthquake under the Earth's surface is known as its focus. True

c. The Richter scale was developed by German seismologist, Charles Richter. False (Charles F. Richter was an American seismologist.)

d. The three kinds of volcanoes are active, dormant, and extinct. True

e. The intensity of an earthquake is measured with the help of a seismograph. False (A seismograph records the seismic waves; the intensity is measured on the Modified Mercalli Intensity scale or other similar scales.)

  1. Answer the following questions in one or two words:

a. What was the name of the supercontinent which was once joined together?


b. What are the forces that act on the surface of the Earth called?

Exogenic forces

c. The word volcano is derived from the island of which country?


d. The large-scale displacement of the rock structures is known as


  1. Here are brief answers to the questions:

a. What do you mean by volcano?

A volcano is an opening in the Earth's crust through which molten rock, ash, and gases erupt. It forms when magma from within the Earth's mantle makes its way to the surface.

b. How can the damage caused by earthquakes be reduced?

Damage caused by earthquakes can be reduced through earthquake-resistant construction, early warning systems, public education and preparedness, strict building codes, and land-use planning to avoid constructing buildings in high-risk areas.

c. What is faulting?

Faulting is the process by which rocks break and move along fractures in the Earth's crust due to tectonic forces. This movement can cause earthquakes and result in the displacement of rock layers.

d. What do you mean by lithosphere plates?

Lithosphere plates are large, rigid segments of the Earth's lithosphere (crust and uppermost mantle) that move and interact on the underlying, more fluid asthenosphere. Their interactions cause most of the Earth's seismic and volcanic activity.

e. What are young and old fold mountains?

Young fold mountains are relatively recent in geological terms, characterized by high peaks, deep valleys, and significant tectonic activity (e.g., the Himalayas). Old fold mountains are older, having been formed millions of years ago; they are generally lower, more eroded, and tectonically less active (e.g., the Appalachians).

  1. Answer the following questions in detail.

a. Write a short note on the Theory of Plate Tectonics.

The Theory of Plate Tectonics posits that the Earth's outer shell, or lithosphere, is divided into several large and small plates that float on the semi-fluid asthenosphere beneath them. These tectonic plates move due to the convective currents in the mantle. The movement and interactions of these plates cause various geological phenomena, such as earthquakes, volcanic activity, and the formation of mountain ranges. Plate boundaries are classified into three main types: divergent (where plates move apart), convergent (where plates collide), and transform (where plates slide past each other). This theory explains the distribution of earthquakes and volcanoes, as well as the movement of continents over geological time.

b. Write a short note on the Bhuj Earthquake of 2001.

The Bhuj Earthquake occurred on January 26, 2001, in the Indian state of Gujarat. With a magnitude of 7.7 on the Richter scale, it caused extensive damage and loss of life. The epicenter was near the town of Bhuj. The earthquake resulted in the deaths of around 20,000 people, injured over 167,000, and left hundreds of thousands homeless. Buildings, infrastructure, and historical sites were destroyed or severely damaged. The disaster highlighted the need for improved building codes and disaster preparedness in India and led to significant advancements in the country's disaster management strategies.

c. Give a brief account of the distribution of volcanoes.

Volcanoes are primarily found along tectonic plate boundaries. Major volcanic regions include:

The Ring of Fire around the Pacific Ocean, which contains about 75% of the world's active volcanoes.

Mid-Ocean Ridges, such as the Mid-Atlantic Ridge, where tectonic plates are diverging and new crust is formed.

Subduction Zones, like the Andes in South America and the Cascades in North America, where an oceanic plate is being forced beneath a continental plate.

Rift Valleys, such as the East African Rift, where plates are pulling apart.

Hotspots, like those forming the Hawaiian Islands, where plumes of hot mantle material rise towards the surface independently of plate boundaries.

d. Explain the types of volcanoes:

Active Volcanoes

Active volcanoes are those that have erupted recently and are likely to erupt again in the near future. They exhibit ongoing or periodic activity, including the emission of gases, steam, ash, or lava. Examples of active volcanoes include:

Mount Etna in Italy

Kilauea in Hawaii

Mount St. Helens in the USA

Dormant Volcanoes

Dormant volcanoes are those that have not erupted in recent history but have the potential to erupt again. These volcanoes are "sleeping" and could become active at any time if conditions change. Examples of dormant volcanoes include:

Mount Fuji in Japan

Mount Rainier in the USA

Mount Kilimanjaro in Tanzania

Extinct Volcanoes

Extinct volcanoes are those that have not erupted for tens of thousands of years and are not expected to erupt again. They no longer have a magma supply and are considered geologically inactive. Examples of extinct volcanoes include:

Mount Thielsen in Oregon, USA

Kohala in Hawaii

Ben Nevis in Scotland

These classifications help scientists assess volcanic hazards and predict future activity.

e. Explain the formation of major landforms.

Major landforms are created by a combination of tectonic activity, weathering, erosion, and deposition:

Mountains: Formed by tectonic forces through the collision of plates (fold mountains like the Himalayas), volcanic activity (volcanic mountains like Mount Kilimanjaro), or faulting (block mountains like the Sierra Nevada).

Plains: Formed by the accumulation of sediments over long periods, often in river basins (alluvial plains like the Indo-Gangetic Plain).

Plateaus: Elevated flat-topped areas formed by volcanic activity (like the Deccan Plateau), tectonic uplift, or erosion of surrounding land (dissected plateaus like the Colorado Plateau).

Valleys: Low areas between mountains or hills, formed by river erosion (river valleys like the Grand Canyon) or glacial movement (glacial valleys like the Yosemite Valley).

Deserts: Formed in regions with very low precipitation, shaped by wind erosion and deposition (e.g., the Sahara Desert) and the rain shadow effect (e.g., the Atacama Desert).

Coastal Landforms: Shaped by wave and tidal action, including cliffs, beaches, and estuaries, formed by erosion, deposition, and tectonic activity.

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