Igneous Rocks and Magma Quiz

Questions and Answers

What type of rocks form when magma hardens beneath the Earth's surface?

Extrusive Igneous Rocks

Intrusive Igneous Rocks (correct)

Sedimentary Rocks

Metamorphic Rocks

What type of rocks form when lava hardens?

Metamorphic Rocks

Extrusive Igneous Rocks (correct)

Intrusive Igneous Rocks

Sedimentary Rocks

What is the difference between lava and magma?

Magma is molten material beneath the Earth's crust; when it reaches the surface, it is called lava.

What are two characteristics used to classify igneous rocks?

Texture and composition. Signup and view all the answers

How are igneous rocks classified by texture?

Coarse-grained, fine-grained, glassy, and porphyritic texture. Signup and view all the answers

Explain coarse-grained texture.

Slow cooling of magma or lava results in rocks with large crystals. Signup and view all the answers

Explain fine-grained texture.

Rapid cooling of magma or lava results in rocks with small, interconnected crystals. Signup and view all the answers

Explain glassy texture.

Glassy texture occurs when lava is quenched rapidly, preventing crystallization. Signup and view all the answers

Explain porphyritic texture.

Porphyritic textures develop under changing cooling conditions of magma. Signup and view all the answers

Explain granitic composition.

Granitic composition contains light-colored silicate minerals like quartz and feldspar. Signup and view all the answers

Explain basaltic composition.

Basaltic composition includes dark silicate minerals and/or plagioclase feldspar. Signup and view all the answers

Explain andesitic composition.

Andesitic composition falls between basaltic and granitic compositions. Signup and view all the answers

Explain ultramafic composition.

Ultramafic igneous rocks are composed almost entirely of dark silicate minerals. Signup and view all the answers

Study Notes

Igneous Rocks Overview

Intrusive igneous rocks form from magma that solidifies beneath the Earth's surface.
Extrusive igneous rocks form from lava that solidifies on the Earth's surface.

Magma vs. Lava

Magma is molten material found beneath the Earth's crust, often accumulating in magma chambers.
When magma erupts through a volcano, it is referred to as lava.

Classification of Igneous Rocks

Igneous rocks are classified based on two primary characteristics: texture and composition.

Texture Classifications

Coarse-grained texture: Results from slow cooling of magma or lava, leading to large crystal formations.
Fine-grained texture: Results from rapid cooling, resulting in small, interconnected crystals.
Glassy texture: Forms when lava is cooled rapidly during volcanic eruptions, preventing crystallization.
Porphyritic texture: Develops when cooling conditions change quickly, producing varied crystal sizes.

Composition Classifications

Granitic composition: Consists primarily of light-colored silicate minerals such as quartz and feldspar.
Basaltic composition: Contains dark silicate minerals and plagioclase feldspar.
Andesitic composition: Has mineral composition intermediate between basaltic and granitic rocks.
Ultramafic composition: Nearly entirely composed of dark silicate minerals.

Description

Test your understanding of igneous rocks with this quiz. Explore the differences between intrusive and extrusive igneous rocks, as well as the fundamental concepts of magma and lava. Perfect for geology enthusiasts and students alike!