Examkin

Question

Difficulty: MediumRock Types, Formation, and Economic Importance

A civil engineering firm in Nigeria requires a coarse-grained, highly durable rock with high compressive strength for constructing heavy building foundations and road monuments. Which rock type best fulfills this requirement, and what is its primary mode of origin?

  1. Granite, formed through the slow cooling and crystallization of magma deep beneath the Earth's surfaceAnswer
  2. B
    Marble, formed through the accumulation and compaction of organic marine sediments
  3. C
    Basalt, formed through the in-situ chemical weathering and mechanical breakdown of surface rocks
  4. D
    Slate, formed through the deposition and consolidation of fine clay particles in river basins

Answer

Granite, formed through the slow cooling and crystallization of magma deep beneath the Earth's surface
Granite is an intrusive (plutonic) igneous rock. Because magma cools slowly beneath the Earth's crust, large mineral crystals form, giving it a coarse-grained texture and immense structural strength. This makes it an ideal material for foundation construction, aggregate production, and monuments.

Step-by-Step Solution

1
Identify the required rock characteristics described in the engineering scenario
The target rock must be coarse-grained (phaneritic), exceptionally durable, and resistant to high pressure.
Engineering applications such as heavy foundations demand plutonic igneous rocks with interlocking mineral crystals.
2
Evaluate the geological origin of candidate rock types
Granite forms as intrusive magma cools slowly deep underground, allowing large crystals of quartz and feldspar to grow, imparting high strength and coarse texture.
Slow cooling underground produces plutonic igneous rocks, whereas rapid surface cooling produces fine-grained volcanic rocks like basalt.

Key Concept

Classification and Economic Importance of Igneous Rocks
Rate this question

Topics

Rock Types, Formation, and Economic Importance

More questions from this topic