Social Science STD 7 Chapter 10: Earth's Internal Composition and Landforms - Exercises

1. (A) Match the following correctly:

(B) Fill in the blanks:

1. 1. Inner most layer of the earth is known as .........

   core

2. 2. ......... stone is used to grind grains.

   Granite

3. 3. The place where the vibration starts below the surface is called ......... center.

   focus

4. 4. The wall like topography formed due to erosion of the ocean waves is known as .........

   stacks

5. 5. As the speed of the wind decreases and soil particles spread on the ground, it is known as .........

   loess

2. Answer the following questions in one sentence:

1. 1. Which minerals are mainly composed in SiAl layer?

   The SiAl layer is mainly composed of Silica (Si) and Alumina (Al).

2. 2. Name the three main types of rocks.

   The three main types of rocks are Igneous, Sedimentary, and Metamorphic rocks.

3. 3. What are the intrusive igneous rocks?

   Intrusive igneous rocks are formed when molten magma cools down slowly and solidifies deep inside the earth's crust, resulting in a large-grained structure like granite.

4. 4. What is Endogenic force?

   Endogenic forces are the movements or forces that are generated in the interior of the earth, such as earthquakes and volcanic eruptions.

5. 5. What is waterfall?

   A waterfall is formed when a river tumbles straight down at a steep angle over very hard rocks or down a valley.

3. Write a short note on:

1. 1. Sial and Sima.

   Sial	Sima
   1. This layer forms the continental masses. 2. It is primarily composed of Silica (Si) and Alumina (Al). 3. This layer is about 35 km thick.	1. This layer forms the oceanic crust. 2. It consists mainly of Silica (Si) and Magnesium (Ma). 3. This layer is thinner than the Sial layer and is found beneath the oceans.

2. 2. Explain the function of wind with example.

   Wind is an active agent of both erosion and deposition, especially in desert regions. It erodes the softer, lower parts of rocks faster than the harder, upper parts, creating formations like mushroom rocks. When wind lifts and transports sand from one place to another and then stops, it deposits the sand in low, hill-like structures called sand dunes or barchans, which are commonly seen in Rajasthan. When large deposits of this wind-blown sand accumulate, they are called loess, with massive deposits found in China.

3. 3. Explain the function of metamorphic rocks with example.

   Metamorphic rocks are formed when igneous and sedimentary rocks are subjected to immense heat and pressure, causing them to change their form. This process can alter the rock's structure and composition. For example, clay transforms into slate, and limestone changes into marble. These rocks are highly useful in construction and other industries due to their durability and aesthetic qualities.

4. Answer the following questions:

1. 1. Explain the internal structure of the earth with diagram.

   The Earth's internal structure is composed of several layers, much like an onion. The outermost and thinnest layer is the Crust, which is about 35 km thick on the continents. Below the crust is the Mantle, extending to a depth of 2900 km. The innermost layer is the Core, with a radius of about 3500 km. The core is made of nickel and iron and has very high temperature, pressure, and density. The text also divides the core into the outer and inner core.
   

2. 2. Explain, types of rocks with example.

   Rocks are classified into three types based on their formation process:

   • Igneous Rocks: Formed when molten magma or lava cools and solidifies. Examples include basalt (extrusive) and granite (intrusive).
   • Sedimentary Rocks: Formed from compressed and hardened layers of sediments, which are small particles broken down from other rocks and deposited by natural forces. An example is sandstone, which is made from grains of sand.
   • Metamorphic Rocks: Formed when existing igneous and sedimentary rocks are transformed by great heat and pressure. Examples include slate (from clay) and marble (from limestone).

3. 3. Explain the topography (features) of a river or glacier.

   A river's topography is shaped by erosion and deposition. As a river flows, it creates waterfalls where it tumbles over hard rocks. When it enters the plains, it forms large bends called meanders. Continuous erosion and deposition can cut off a meander loop, forming an oxbow lake. During floods, a river deposits alluvium, creating a fertile floodplain, and raised banks called levees.
   A glacier, a "river of ice," erodes the landscape by bulldozing rocks, forming characteristic U-shaped valleys. When the ice melts, these hollows can fill with water, forming lakes. The material carried by a glacier is deposited in a hill-like landform called a Drumlin.