22 Questions
Which type of rock is formed from magma that solidifies underneath the Earth's crust?
Granite
What is a characteristic of extrusive igneous rocks due to the rapid cooling of lava on the Earth's surface?
Vesicle-rich appearance
Which intrusive igneous body is composed of several smaller plutons and can reach hundreds of kilometers in length?
Batholith
What is the example of a dike mentioned in the text?
Mackenzie dike swarm in the Northwest Territories, Canada
What type of magma forms pumice, a light-colored, low density, and vesicle-rich extrusive igneous rock?
Felsic magma
What is the example of a sill mentioned in the text?
Dolerite sills in Karroo, South Africa
What is the term for large igneous bodies that solidify near the Earth's surface and are only exposed when overlying rocks erode?
Pluton
What may displace intrusive bodies and change their original orientation?
Deformations like folding and faulting
What are igneous rocks formed from?
Solidified magma
What causes magma to rise to the Earth's surface?
It is less dense and more buoyant than the surrounding rock
What are the conditions required for rocks to melt and form magma?
High temperature, decreased pressure, presence of volatiles
What type of rocks are formed when magma is trapped underneath the surface and slowly cools?
Intrusive or plutonic rocks
Where are melts commonly found?
Boundaries between tectonic plates or hot spots
What is the source of heat that partially melts small amounts of rocks in the upper mantle?
Radioactive decay occurring in the Earth's core
What is the characteristic of extrusive igneous rocks due to the rapid cooling of lava on the Earth's surface?
Fine-grained texture
What are the three main types of rocks observed on the Earth's surface?
Igneous, sedimentary, and metamorphic rocks
How are igneous rocks formed?
From the solidification of molten material called magma
What makes magma rise to the Earth's surface?
It is less dense and more buoyant than the surrounding rock
Where are the rising melts commonly found?
In boundaries between tectonic plates or hot spots
What conditions are required for rocks to melt?
The temperature should be at least near the temperature in the upper mantle, the pressure should decrease, and volatiles such as water should be present
What type of rocks are formed when magma is trapped underneath the surface and slowly cools?
Intrusive or plutonic rocks
What is the source of heat that partially melts small amounts of rocks located in the upper mantle?
Radioactive decay occurring in the Earth's core
Study Notes
Intrusive vs Extrusive Igneous Rocks
- Volcanic rocks are formed when molten material, called lava, is extruded onto the Earth's surface through volcanic vents and fissures.
- The rapid cooling of lava on the surface results in fine-grained or glassy-textured rocks with trapped gases known as vesicles.
- Pumice is an example of extrusive igneous rock, characterized by its light-colored, low density, and vesicle-rich appearance, formed from felsic magma.
- Plutonic rocks, or intrusive rocks, form from magma that does not reach the Earth's surface and solidifies slowly underneath the crust.
- Granite is an example of intrusive igneous rock, formed by slow cooling of viscous felsic magma, resulting in coarse-grained, light-colored crystalline texture.
- Plutons are large igneous bodies that solidify near the Earth's surface and are only exposed when overlying rocks erode, forming batholiths, dikes, and sills.
- Batholiths are irregularly shaped plutons composed of several smaller plutons, such as granite, quartz monzonite, or diorite, and can reach hundreds of kilometers in length.
- Dikes and sills are formed when magma intrudes pre-existing rock bodies and crystallizes as sheet intrusions, with dikes cutting across rock layers and sills occurring parallel to bedding planes.
- An example of a dike is the Mackenzie dike swarm in the Northwest Territories, Canada, while a sill example is the Dolerite sills in Karroo, South Africa.
- Plutons can also form batholiths, such as the Sierra Nevada Batholith in California and Pikes Peak granite in Colorado.
- Deformations in the rock, like folding and faulting, may displace intrusive bodies and change their original orientation.
- Understanding the differences between intrusive and extrusive rocks is essential in geology and has practical applications in fields like construction and resource exploration.
Test your knowledge of intrusive and extrusive igneous rocks with this quiz! Explore the formation, characteristics, and examples of volcanic and plutonic rocks, including their impact on geology and practical applications in various fields.
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