Test: Inside Our Earth - UPSC

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.

Sandstone is made of sand grains (0.05mm to 2mm) that may have been deposited in the sea, by rivers, or in deserts, and later cemented together by minerals precipitated from groundwater.

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.

The Earth's outer core has a radius of about 3,500 km. The inner core is more than 5,000 °C hot but in solid-state due to the high pressure. The outer core is liquid and somewhat cooler.

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.

Ferrous means generally "containing iron". It is derived from the Latin word Ferrum ("iron").
Example: Steel, Pig iron, and alloys of iron with other metals (such as stainless steel).

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.