Olympiad Test Level 1: Our Earth and Universe- 2 - Class 7 MCQ

Widest section of the 'Earth' is known as:
The widest section of the 'Earth' refers to the part with the largest diameter. This section is known as the mantle.
Explanation:
The Earth is composed of several layers, including the inner core, outer core, mantle, and crust. Among these layers, the mantle is the widest section. Here's a breakdown of the Earth's structure and why the mantle is considered the widest section:
1. Inner Core:
- Located at the center of the Earth.
- Composed mainly of solid iron and nickel.
- Has a radius of approximately 1,220 kilometers.
2. Outer Core:
- Surrounds the inner core.
- Composed of liquid iron and nickel.
- Has a radius of approximately 2,200 kilometers.
3. Mantle:
- Lies between the outer core and the Earth's crust.
- Composed of solid rock that can flow slowly over long periods of time.
- Accounts for approximately 84% of the Earth's volume.
- Has an average thickness of about 2,900 kilometers.
4. Crust:
- The Earth's outermost layer.
- Composed of solid rock and soil.
- Varies in thickness, with oceanic crust being thinner than continental crust.
- Has an average thickness of about 30 kilometers.
Therefore, based on the Earth's structure, it is the mantle that is considered the widest section of the Earth.

The top layer of earth in which the plants grow is known as Soil.

The Chipko movement started from:
The Chipko movement, also known as the Chipko Andolan, originated in Reni, a village in the Garhwal region of Uttarakhand, India.
Explanation:
The Chipko movement was a grassroots environmental movement that emerged in the 1970s in response to the deforestation and degradation of forests in the Himalayan region. Here is a detailed explanation of the movement:
1. Reni in Garhwal:
- The Chipko movement started in the village of Reni in the Garhwal region, which is now a part of Uttarakhand state in India.
- In 1973, the movement gained prominence when the local women of Reni, led by Gaura Devi, hugged the trees to prevent them from being felled by loggers.
2. Objective of the movement:
- The main objective of the Chipko movement was to protect the forests from commercial exploitation and maintain the ecological balance.
- The movement aimed to raise awareness about the importance of forests and the need for sustainable development.
3. Methods used by the activists:
- The activists, mostly women, employed non-violent methods to protect the forests.
- They hugged the trees and formed human chains around them to prevent their felling.
- They also used slogans, songs, and awareness campaigns to mobilize support for their cause.
4. Impact and success:
- The Chipko movement gained national and international attention, highlighting the issue of deforestation and the rights of local communities.
- The movement led to the recognition of community rights over forests and the formulation of policies for sustainable forest management.
- It also inspired similar movements in other parts of India and around the world.
In conclusion, the Chipko movement started in Reni, a village in the Garhwal region of Uttarakhand, as a response to deforestation. It played a significant role in raising awareness about environmental conservation and community rights over forests.

The farthest planet of our Solar System is Neptune.
Neptune is the eighth and farthest planet from the Sun. It is located at an average distance of about 2.8 billion miles (4.5 billion kilometers) from the Sun.
Here are the reasons why Neptune is the farthest planet:
- Distance from the Sun: Neptune is located at an average distance of 2.8 billion miles from the Sun, making it the farthest planet in our Solar System.
- Orbit: Neptune has a highly elliptical orbit, which means it deviates from a perfect circle. This elliptical orbit takes Neptune to its closest point to the Sun (perihelion) and its farthest point from the Sun (aphelion). Due to its elongated orbit, Neptune spends most of its time farthest from the Sun.
- Slow orbit: Neptune takes the longest time to complete one orbit around the Sun compared to the other planets in our Solar System. It takes approximately 165 Earth years for Neptune to complete one orbit. This slow orbit contributes to its position as the farthest planet.
- Discovery: Neptune was discovered in 1846 by astronomers Urbain Le Verrier and Johann Galle. Its discovery was based on mathematical predictions and observations of the gravitational influence it had on the orbit of Uranus. This discovery revealed the existence of a previously unknown planet beyond Uranus, solidifying Neptune's status as the farthest planet in our Solar System.
In conclusion, Neptune is the farthest planet of our Solar System due to its distance from the Sun, elliptical orbit, slow orbit, and its discovery as a result of the gravitational influences on Uranus.

Earth Hour is organized by the World
Wildlife Fund (WWF). With almost 5 million supporters and a global network in over 100 countries/territories, it’s one of the world’s largest and most respected independent conservation organizations. WWF is mission is to stop the degradation of the Earth’s natural environment and build a future where people live in harmony with nature.

The correct sequence of Earth from the interior to the surface is as follows:
1. Core:
- The innermost layer of the Earth is the core.
- It is composed of two parts: the inner core and the outer core.
- The inner core is solid, while the outer core is in a liquid state.
- The core is primarily made up of iron and nickel.
2. Mantle:
- The mantle is the layer between the core and the crust.
- It is the thickest layer of the Earth.
- The mantle is mainly composed of solid rock, but it is capable of flowing over long periods of time.
- It is divided into two sections: the upper mantle and the lower mantle.
3. Crust:
- The crust is the outermost layer of the Earth.
- It is a relatively thin layer compared to the core and mantle.
- The crust is composed of solid rocks and minerals.
- It is divided into two types: continental crust and oceanic crust.
Therefore, the correct sequence of Earth from the interior to the surface is Core > Mantle > Crust (Option B).

To identify the planet that takes the maximum time for one spin on its axis, we need to analyze the given options: Venus, Mercury, Saturn, and Uranus. Let's go through each option and determine the correct answer.
Venus:
- Venus is the second planet from the Sun in our solar system.
- It is known for its thick atmosphere and extreme temperatures.
- Venus takes about 243 Earth days to complete one rotation on its axis.
Mercury:
- Mercury is the closest planet to the Sun.
- It is the smallest planet in our solar system.
- Mercury takes about 59 Earth days to complete one rotation on its axis.
Saturn:
- Saturn is the sixth planet from the Sun in our solar system.
- It is famous for its beautiful rings.
- Saturn takes about 10 hours and 33 minutes to complete one rotation on its axis.
Uranus:
- Uranus is the seventh planet from the Sun in our solar system.
- It is an ice giant planet.
- Uranus takes about 17 hours and 14 minutes to complete one rotation on its axis.
From the given options, it is clear that the planet that takes the maximum time for one spin on its axis is Mercury. It takes approximately 59 Earth days to complete one rotation.

Water harvesting is a method which:
1. Increases ground water level: Water harvesting techniques help to replenish the underground water table by collecting and storing rainwater. This increases the availability of water in the groundwater reservoir.
2. Is practiced in modern days: Water harvesting is a practice that is widely used in modern times to ensure the sustainable management of water resources. It is implemented in both rural and urban areas to conserve water and mitigate water scarcity.
3. Has a direct relation with groundwater: Water harvesting techniques, such as rooftop rainwater harvesting and groundwater recharge, directly contribute to the replenishment of groundwater reserves. These methods allow rainwater to percolate into the ground, thereby recharging the aquifers.
4. Does not decrease ground water level: On the contrary, water harvesting helps to prevent the depletion of groundwater resources. By capturing and storing rainwater, it reduces the reliance on groundwater extraction, thus maintaining or even increasing the groundwater level.
In conclusion, water harvesting is a method that increases the groundwater level, is widely practiced in modern days, and has a direct relation with groundwater. It is an effective approach to conserve water and ensure the sustainable management of water resources.

Oxides of nitrogen and sulphur dissolves in rainwater to form corresponding acides.
This result into acid rain.

Answer:
To identify which constellation consists of seven main stars, we need to examine the given options and their characteristics.
Option A: Ursa Major
- Ursa Major, also known as the Great Bear, is a prominent constellation in the northern sky.
- It consists of seven bright stars that form the shape of a dipper or a saucepan.
- However, these seven stars are not the main stars of Ursa Major, but rather part of an asterism called the Big Dipper.
Option B: Ursa Minor
- Ursa Minor, also known as the Little Bear or the Little Dipper, is another constellation in the northern sky.
- Ursa Minor consists of seven main stars that form the shape of a smaller dipper or saucepan.
- These seven stars, including Polaris (the North Star), are the main stars of Ursa Minor.
Option C: Hercules
- Hercules is a constellation located in the northern sky.
- It is known for its distinctive shape, which resembles a torso and a head of a mythical hero.
- However, Hercules does not consist of seven main stars.
Option D: Lyra
- Lyra is a small constellation in the northern sky.
- It is notable for its bright star Vega, one of the brightest stars in the night sky.
- Lyra does not consist of seven main stars.
Conclusion:
Based on the given options, the constellation that consists of seven main stars is Ursa Minor (Option B).