Igneous Rocks and Magma Types

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Questions and Answers

Which mineral is formed last as magma crystallizes?

Gold

Platinum

Quartz (correct)

Nickel

Dikes and sills refer to the same type of igneous intrusion.

False

What are the main components of magma that have the lowest melting points?

Silica and oxygen

The largest igneous intrusions are known as __________.

batholiths Signup and view all the answers

Match the following igneous intrusions with their descriptions:

Dike = Vertical sheet of magma Sill = Horizontal sheet of magma Laccolith = Domed mass of magma Volcanic neck = Solidified magma plug of an inactive volcano Signup and view all the answers

What type of crystals crystallize first as the temperature of magma drops?

Minerals with the highest melting points Signup and view all the answers

What type of igneous rock is formed when magma cools slowly beneath the Earth's surface?

Intrusive Igneous Rocks Signup and view all the answers

Quartz veins are rare because quartz is usually formed immediately after other minerals crystallize.

False Signup and view all the answers

Extrusive igneous rocks have a coarse-grain texture.

False Signup and view all the answers

What are the three minerals commonly found in igneous rock formations?

Platinum, chromium, nickel Signup and view all the answers

What is the primary difference between felsic and mafic magma?

Felsic magma contains large amounts of silica, while mafic magma contains little silica. Signup and view all the answers

Magma that reaches Earth’s surface is referred to as ______.

lava Signup and view all the answers

Which rock is formed from felsic magma?

Granite Signup and view all the answers

Match the type of magma with its characteristics:

Felsic = Light in color, high silica content Mafic = Dark and dense, low silica content Intermediate = Medium grays and greens, moderate silica content Signup and view all the answers

The texture of igneous rocks is determined by the cooling rate of magma.

True Signup and view all the answers

What are the characteristics of intrusive igneous rocks?

Intrusive igneous rocks have a coarse-grain texture and form slowly beneath the Earth's surface. Signup and view all the answers

Study Notes

Igneous Rocks

Igneous rocks form from the crystallization of magma
The location of cooling magma determines the rate of cooling and thus the texture of the resulting rock
Intrusive igneous rocks form deep beneath Earth's surface
Intrusive rocks cool slowly, resulting in large crystals
Extrusive igneous rocks form when magma reaches Earth's surface (lava) and cool quickly
Extrusive rocks cool rapidly, resulting in microscopic crystals
The type of magma (felsic, mafic, intermediate) determines the rock's color

Magma Types

Felsic magma: high silica content, thick, slow-moving, light-colored rocks (e.g., granite)
Mafic magma: low silica content, hot, fluid, dark-colored rocks (e.g., gabbro)
Intermediate magma: moderate silica content, viscosity between felsic and mafic magmas, medium-colored rocks

Igneous Intrusions

Intrusions are formations of magma that push into existing rock
Plutons are the general term for igneous intrusions
Dikes are sheet-like intrusions that run vertically through existing rock
Sills are sheet-like intrusions that run horizontally through existing rock
Laccoliths are large, dome-shaped intrusions
Volcanic necks are remnants of solidified magma after a volcano erodes
Batholiths are large, complex intrusions that form the cores of mountain ranges

Practice Questions

Question 1: Create a Venn diagram comparing felsic and mafic magmas.
Question 2: Different cooling rates lead to different textures in igneous rocks.
Question 3: A laccolith forms when magma is stiff and unable to spread, instead bulging upwards.
Question 4: Obsidian's glassy texture makes it a better cutting tool than gabbro's coarse texture.
Question 5: Magma flowing easily suggests low silica content; high silica magma is thick and slow-moving.

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Description

This quiz covers the formation and characteristics of igneous rocks, focusing on their origins from magma. You will learn about intrusive and extrusive rocks, the types of magma, and the effects on rock texture and color. Test your knowledge of igneous intrusions and their classifications.