Geology Test 21: Igneous Rock and Magma

Questions and Answers

Define Concordant.

Parallel to the grain or layering of the surrounding rock.

Define Magma.

Molten rock material that originates deep within the earth.

Define Igneous Rock.

A type of rock formed from a molten material that has cooled and solidified.

Define Lava.

Molten rock material that reaches the earth's surface due to a volcanic eruption. Signup and view all the answers

How old is the Earth?

4.6 billion years. Signup and view all the answers

What was the first type of rocks to form?

The first rocks formed were igneous. Signup and view all the answers

______ Earth's crust is composed of igneous rocks.

80% Signup and view all the answers

Igneous rocks can be divided into two basic categories.

Extrusive igneous & Intrusive igneous. Signup and view all the answers

Describe extrusive igneous rocks.

Rocks that cool at the surface of the earth, generally due to some type of volcanic eruption. Signup and view all the answers

Describe intrusive igneous rocks.

Igneous rocks that cooled somewhere beneath the surface of the earth. Signup and view all the answers

How are Igneous Rocks classified?

Texture & Mineral composition. Signup and view all the answers

Define Texture.

Refers to the size, shape and arrangement of grains or other constituents within a rock. Signup and view all the answers

Describe Aphanitic.

Extrusive igneous rocks cool quickly at or near Earth's surface. Signup and view all the answers

Describe Glassy.

Texture contains no crystals at all, and is formed by extremely rapid cooling. Signup and view all the answers

Describe Porphyritic.

Texture includes 2 distinct crystal sizes. Signup and view all the answers

Describe Pegmatitic.

An extremely coarse-grained igneous rock, forms when magma cools very slowly at depth. Signup and view all the answers

Describe Phaneritic.

Intrusive igneous rocks cool slowly deep beneath earth's surface. Signup and view all the answers

What is the correlation of Mineral Composition and Color of Igneous Rocks?

The color gives a clue as to its composition. Signup and view all the answers

What are oceanic plates composed of?

More dense low silica rocks. Signup and view all the answers

What is the correlation between Density and Composition?

The dark low silica rocks are more dense than the light colored high silica rocks. Signup and view all the answers

What are continental plates composed of?

Less dense high silica rocks. Signup and view all the answers

Know the Common Igneous Rocks and how they are Organized by Composition.

Study guide. Signup and view all the answers

Describe in detail Bowen's Reaction Series. Why is it important?

It describes the sequence of mineral formation from cooling magma. Signup and view all the answers

Define Discordant.

Cuts against the grain or layering of the surrounding rock. Signup and view all the answers

How are Igneous rock bodies subdivided?

Intrusive igneous rock bodies & Extrusive igneous rock bodies. Signup and view all the answers

Define Pluton. How are they classified?

A large body of intrusive igneous rock formed below the earth's surface. Signup and view all the answers

Study Notes

Key Definitions

Concordant: Describes rock layers that run parallel to the surrounding geological features.
Magma: Molten rock material located deep within the Earth.
Lava: Magma that reaches the Earth's surface through volcanic activity.
Igneous Rock: Rock formed through the cooling and solidification of molten material.

Earth Facts

The Earth is approximately 4.6 billion years old.
Igneous rocks were the first type of rocks to form on Earth.
Approximately 80% of the Earth's crust is composed of igneous rocks.

Types of Igneous Rocks

Extrusive Igneous Rocks: Formed by cooling at the Earth's surface, typically from volcanic eruptions.
Intrusive Igneous Rocks: Formed from cooling beneath the Earth’s surface; visible at the surface due to erosion or uplift.

Classification of Igneous Rocks

Classified based on texture and mineral composition.

Texture Definitions

Aphanitic: Texture of extrusive igneous rocks that cool quickly at or near the surface.
Glassy: Texture with no visible crystals formed by rapid cooling.
Porphyritic: Contains two crystal sizes; larger phenocrysts formed slowly underground and smaller groundmass formed rapidly at the surface.
Pegmatitic: Extremely coarse-grained rocks formed from very slow cooling of magma.
Phaneritic: Intrusive rocks that cool slowly beneath the Earth's surface.

Mineral Composition and Color

Igneous rock color indicates its mineral composition:
- High Silica: Light-colored minerals, such as those found in granite, diorite, and andesite.
- Low Silica: Dark-colored minerals with higher iron, magnesium, and calcium content, such as in gabbro and peridotite.

Types of Plate Composition

Oceanic Plates: Composed of denser, low-silica rocks, often resting below sea level.
Continental Plates: Composed of less dense, high-silica rocks that stand high above sea level.

Density Correlation

Low silica rocks tend to be more dense than high silica rocks.

Bowen's Reaction Series

Describes the order in which minerals crystallize from cooling magma; essential for understanding mineral content in igneous rocks and their formation processes.

Rock Bodies Classification

Igneous rock bodies can be subdivided into intrusive and extrusive types.
Pluton: A large body of intrusive igneous rock formed from solidified magma, classified by size and shape.

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Description

This quiz focuses on key concepts in geology, specifically relating to igneous rock, magma, and lava. Learn definitions and properties of these essential geological materials through flashcards. Test your knowledge and enhance your understanding of rock formation processes.