Test: Inside Our Earth - Class 7 MCQ

The thinnest layer of the earth is Crust. It is about 35 km on continental masses & 5 km on ocean floors.

The main mineral constituents:
(i) Continental mass are silica and alumina. It is thus called sial (si-silica and al-alumina).
(ii) The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium).

There are three main types of rock:
(i) Igneous rocks form from molten rock, and rarely have fossils in them.
(ii) Metamorphic rocks have been put under great pressure, heated, squashed or stretched, and fossils do not usually survive these extreme conditions.
(iii) It is only sedimentary rocks that contain fossils.

Thus, option A is correct.

The innermost layer of the earth is known as the core, divided into inner core and outer core.
It comprises of a high concentration of nickel and iron.

The core is the innermost layer, divided into the outer core and the inner core.
It is mainly made up of Nickel and Iron, therefore, it is also called nife.
Its radius is about 3500 km and the temperature and pressure of the central core are very high.

A Fossil is any preserved remains, impression, or trace of any dead organism which was living in the past from a different geological age.
Example: Bones or stone imprints of animals or microbes, exoskeletons, shells, objects preserved in petrified wood, oil, coal, and DNA remnants.

The study of fossils is known as “Palaeontology”. This includes the study about their age, the method of formation, and evolutionary significance. If the age or time of some specimens is over 10,000 old years, they are considered to be fossils.

Thus, option C is correct.

There are three main types of rock: Igneous Rocks, Metamorphic Rocks, and Sedimentary Rocks.

The mantle is the most solid bulk of Earth's interior that lies between core and crust.

• When fiery red molten lava comes out from the interior of the earth and cools down quickly on the earth's surface, it forms rocks called extrusive igneous rocks. These rocks have a very fine-grained structure. An example of extrusive igneous rock is basalt. So, when you see lava cooling fast and forming rocks like basalt, you're looking at extrusive igneous rocks.

Sedimentary rocks are formed from the accumulation and compression of sediments over time. The Deccan plateau, known for its extensive basalt formations, is primarily composed of igneous rocks, particularly basalt, which are formed from solidified lava. So, the statement is False.