Question

Evaluate these statements regarding the formation of Igneous rocks:Which of the statements is/are true?

1. Magma must come out and solidify to form these rocks.
2. They are called primary because they are formed from the destruction of secondary rocks.
3. The root word "Ignis" defines the thermal nature of their origin.

• A. i, iii
• B. All
• C. i, ii
• D. iii only

Answer 1

Answer:

A. i, iii

Igneous Rocks: Formation and Characteristics

• Igneous rocks are formed from the cooling and solidification of molten rock material. This molten material is known as magma when it is beneath the Earth's surface and lava when it erupts onto the surface. Therefore, for igneous rocks to form, this molten material must be extruded (come out) and then solidify.
• Igneous rocks are often referred to as primary or original rocks. This is because they are the first type of rocks to form on Earth from the cooling of molten material. They are not formed from the destruction of other types of rocks (secondary or sedimentary rocks).
• The term 'igneous' is derived from the Latin word 'ignis', which means 'fire'. This etymology accurately reflects the origin of these rocks, as they are formed from the intense heat associated with molten rock.

Types of Igneous Rocks:

• Intrusive Igneous Rocks: These form when magma cools and solidifies slowly beneath the Earth's surface. The slow cooling allows large crystals to form. Examples include Granite and Gabbro.
• Extrusive Igneous Rocks: These form when lava cools and solidifies rapidly on the Earth's surface. The rapid cooling results in small crystals or a glassy texture. Examples include Basalt and Obsidian.

Significance in Geology:

• Igneous rocks provide crucial information about the Earth's internal processes and the composition of the planet's mantle and crust.
• The study of igneous rocks, known as igneous petrology, is fundamental to understanding plate tectonics, volcanic activity, and the formation of mineral deposits.