Granite is an example of?
a. Intrusive
b. Extrusive
c. Clastic
d. Shale
The correct answer and explanation is :
Granite is an example of an intrusive igneous rock.
To understand why granite is classified as intrusive, it’s essential to comprehend the formation processes of igneous rocks. Igneous rocks form from the cooling and solidification of molten rock material known as magma. The environment in which this cooling occurs determines whether the rock is intrusive or extrusive.
Intrusive Igneous Rocks: These rocks form from magma that cools slowly beneath the Earth’s surface. The slow cooling process allows large, visible crystals to develop, resulting in a coarse-grained texture. Granite is a prime example of this category.
Extrusive Igneous Rocks: In contrast, extrusive rocks form from lava that cools rapidly on the Earth’s surface, typically due to volcanic eruptions. The quick cooling doesn’t permit large crystals to form, leading to a fine-grained or even glassy texture. Basalt is a common example of an extrusive igneous rock.
Granite’s Composition and Characteristics: Granite is primarily composed of quartz, feldspar, and mica, giving it a visibly crystalline appearance. The minerals within granite interlock, contributing to its durability and strength. This composition not only provides granite with its characteristic speckled look but also makes it a popular choice for construction and decorative purposes, such as countertops and flooring.
Understanding the Other Options:
- Clastic Rocks: These are sedimentary rocks formed from fragments (clasts) of pre-existing rocks that have been compacted and cemented over time. Sandstone is a typical example of a clastic rock.
- Shale: This is another type of sedimentary rock, characterized by its fine grains and formation from silt and clay particles. Shale often splits into thin layers and is rich in fossils.
In summary, granite’s formation deep within the Earth’s crust, its coarse-grained texture, and its mineral composition all point to its classification as an intrusive igneous rock.
Here is an image of granite showcasing its coarse-grained texture:
