Question

Which of the following is not an intrusive igneous rock?
A) Laccolith
B) Dyke
C) Batholith
D) Basalt

Answer 1

Hint: The solidification of molten rock material produces igneous rocks. There are two fundamental categories. Intrusive igneous rocks crystallised beneath the surface of the Earth, and the gradual cooling permits huge crystals to form. The rocks formed when magma never reaches the surface and cools to form intrusions (dykes, sills, etc.) are known as plutonic or intrusive.

Complete answer:
 Gabbro, diorite, granite, and pegmatite are the names given to intrusive igneous rocks based on their silica content (in ascending order of silica content).

Let us look at the given options.
A) Laccolith: It is a form of igneous intrusion that has split two strata apart, resulting in a dome like structure; the structure's floor is usually horizontal.Laccoliths can be hundreds of metres thick or a few thousand metres thick.Acidic rocks are more abundant in laccoliths than basic rocks.Option A is incorrect since it is an intrusive igneous rock.

B) Dyke: A dyke is a structure that is built into an opening cross-cutting fissure, pushing aside other layers or bodies of rock.An intrusive dike is an igneous body with a high aspect ratio, meaning that its thickness is often substantially less than the other two dimensions.Thus,option B is incorrect.

C)Batholith: A batholith is a huge intrusive igneous rock mass that originates from cooled magma deep inside the Earth's crust and covers an area of more than 100 square kilometres. Felsic or intermediate rock types, such as granite, quartz monzonite, or diorite, are usually invariably found in batholiths.Thus,option C is incorrect.

D)Basalt: Basalt is a dark-colored, fine-grained extrusive igneous rock mostly consisting of plagioclase and pyroxene.It's a mafic extrusive rock that's the most common of all igneous rocks, accounting for about 90% of all volcanic rocks. Basalt lava has a low viscosity due to its low silica content, allowing it to create thin flows that can travel vast distances.Thus,option D is the correct answer.

Hence the correct answer is option 'D'.

Note: Extrusive igneous rocks erupt to the surface and cool rapidly, forming tiny crystals. Some cool quickly enough to turn into amorphous glass. Andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff are examples of these rocks.