Question

Evaluate the following statements regarding Igneous formations:Which of the statements is/are correct?

1. Dykes are horizontal cooling structures of magma.
2. Igneous rocks are often the first stage in the rock cycle, hence called "Primary."
3. Granite is an example of a rock formed from volcanic activity.

• A. All
• B. None of these
• C. 2, 3
• D. 1, 2

Answer 1

Answer:

C. 2, 3

• Igneous rocks are formed from the cooling and solidification of molten rock (magma or lava). They are considered the "Primary Rocks" because they represent the initial stage of rock formation in the rock cycle. They form from the cooling of magma deep within the Earth or lava erupted onto the surface.
• Dykes are a type of intrusive igneous formation. They are formed when magma intrudes into a fissure or crack in pre-existing rock. Unlike horizontal formations, dykes are typically discordant, meaning they cut across the bedding or structure of the host rock and are often oriented vertically or steeply inclined. Horizontal or near-horizontal intrusive bodies are called sills.
• Granite is a common type of intrusive igneous rock. It forms from magma that cools and solidifies slowly beneath the Earth's surface. This slow cooling allows large crystals to form, giving granite its characteristic granular texture. Rocks formed from volcanic activity, where lava cools quickly on the surface, are called extrusive igneous rocks and typically have smaller crystals (e.g., basalt, obsidian). Therefore, granite is not formed from volcanic activity but from plutonic processes deep within the crust.
• The rock cycle describes the continuous process by which rocks are transformed from one type to another. Igneous rocks are the starting point, which can then be weathered and eroded into sediment (forming sedimentary rocks) or subjected to heat and pressure (forming metamorphic rocks).