NCERT Class 7 Geography — Chapter 1: Inside Our Earth

mcqeasy

The oceanic crust mainly consists of which of the following mineral constituents?

Official previous-year question

Verified 1 Aug 2026.

Options

ASilica and Magnesium
BSilica and Alumina
CIron and Magnesium
DNickel and Iron

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Solution

The correct option is

Silica and Magnesium

Explanation

The Earth's crust is the outermost solid shell of the planet, categorized into continental and oceanic crust based on composition, density, and thickness.

Oceanic Crust (SIMA): The oceanic crust is thinner (5–10 km) and denser than the continental crust. It is primarily composed of Silica and Magnesium. Due to these dominant constituents, it is often referred to as SIMA. It is largely basaltic in nature.
Continental Crust (SIAL): The continental crust is thicker and less dense. It mainly consists of Silica and Alumina, leading to the acronym SIAL. It is largely granitic in nature.
Core (NIFE): The core of the Earth is composed primarily of heavy metals, specifically Nickel and Iron, referred to as NIFE.

Key Takeaway: The oceanic crust is characterized by the composition of Silica and Magnesium (SIMA), whereas the continental crust is characterized by Silica and Alumina (SIAL).

Your note

More from Chapter 1: Inside Our Earth

Consider the following statements regarding the interior of the Earth: 1. The crust is the thickest layer of the Earth. 2. The oceanic crust is thinner than the continental crust. 3. The mantle extends up to a depth of only 100 km. Which of the statements given above is/are correct?

medium

With reference to the composition of the Earth’s crust, the term ‘Sial’ refers to which of the following combinations?

easy

Consider the following statements regarding the Earth's core: 1. It is the innermost layer with a radius of about 3500 km. 2. It is mainly composed of silica and magnesium. 3. It has very high temperature and pressure. Which of the statements given above is/are correct?

medium

Which of the following correctly represents the volume composition of the Earth’s layers?

medium

Consider the following pairs regarding rock types and their word origins: 1. Igneous : Latin word meaning 'fire' 2. Sedimentary : Latin word meaning 'settle down' 3. Metamorphic : Greek word meaning 'change of form' 4. Fossils : Latin word meaning 'hard rock' How many of the above pairs are correctly matched?

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The correct option is

Silica and Magnesium

Explanation

The Earth's crust is the outermost solid shell of the planet, categorized into continental and oceanic crust based on composition, density, and thickness.

Oceanic Crust (SIMA): The oceanic crust is thinner (5–10 km) and denser than the continental crust. It is primarily composed of Silica and Magnesium. Due to these dominant constituents, it is often referred to as SIMA. It is largely basaltic in nature.
Continental Crust (SIAL): The continental crust is thicker and less dense. It mainly consists of Silica and Alumina, leading to the acronym SIAL. It is largely granitic in nature.
Core (NIFE): The core of the Earth is composed primarily of heavy metals, specifically Nickel and Iron, referred to as NIFE.

Key Takeaway: The oceanic crust is characterized by the composition of Silica and Magnesium (SIMA), whereas the continental crust is characterized by Silica and Alumina (SIAL).