Question

Primary rocks that are of thermal origin are _____________.
A.Metamorphic rocks
B.Sedimentary rocks
C.Igneous rocks
D.None of these

Answer 1

Hint: Primary rocks also known as crystalline rocks are formed during the geological ages. They have no organic matter, like granite, schist or gneiss.

Complete Step by Step answer: These rocks are of three types: sedimentary rocks, metamorphic rocks and igneous rocks. These rocks are also often referred to parent rocks because other rocks are formed from primary rocks. Therefore, primary rocks are the rocks that begin the rock cycle.
Primary rocks that are of thermal origin are igneous rocks. These rocks are formed when the molten magma solidifies.
Option A. Metamorphic rocks are a type of Primary rock that starts off as another rock but take their final formation later on. They are not of thermal origin.
Option B. Sedimentary rocks are another type of primary rock that is formed due to cementing and accumulation of minerals in the earth’s surface. They are also not of thermal origin.
Option C. Igneous rocks are those primary rocks that are formed through the moulding of the molten magma. These rocks are of primary origin.
Option D. None of these is not the correct answer to this question.
The correct answer to this question is option C - Igneous rocks. These are the only types of Primary rocks that are of thermal origin.

Note: Thermal origin is a region that is hot or warm. Thus, the above question tells us about primary rocks that are formed in thermal or warm and hot regions. These are the rocks that are formed due to natural heat present in the earth.