Environmental Engineering Chapter 3 Homework Rock Cycle And Plate Tectonics Plate Tectonics

Learning Objectives

After reading and studying this chapter, students should

▪ Understand minerals in terms of their chemistry and internal structure

▪ Know the major groups of important rock-forming minerals and their environmental

significance

▪ Understand the rock cycle and how it interacts with plate tectonics

▪ Know the three rock laws

▪ Know the basic rock types and their environmental significance

▪ Know the basic rock structures

Chapter Summary

This chapter focuses on minerals, rocks, rock structures, and the environmental importance thereof.

The chapter opens with a case history of the asbestos controversy, and follows with discussions of

mineral characteristics, bonding, and mineral groups. The chapter then turns to the rock cycle and

Chapter Outline

I. Minerals

A. What is a mineral?

B. Atoms and elements

1. Atoms and elements

2. Conceptual model of an atom

a. atoms are composed of three subatomic particles: protons, neutrons, and electrons

3. isotopes

4. Why are isotopes important in studying the environment?

C. Mineral chemistry: compounds

3

Minerals and Rocks

1. formal definition of mineral: element or chemical compound that is naturally formed, is

2. minerals and chemical bonding

a. four types of chemical bonds

2. ionic: atoms attracted by opposite charges imparted by gain or loss of electrons

4. metallic: electrons shared by all atoms of the solid mass rather than by specific atoms

b. bonding determines important mineral properties

3. crystalline structure of minerals

a. crystalline structure is the orderly, regularly repeating geometric patterns of atoms

II. Important rock-forming minerals

A. Common minerals

1. more than 4000 known minerals

2. hand specimen identification involves appearance and physical properties

a. mineral properties summarized in Appendix A

3. weathering (See A Closer Look: Weathering)

4. Geologists learn to identify minerals using pattern recognition

a. Clues such as color, specific gravity, crystal form, cleavage, etc.

B. Silicates

1. silicon and oxygen comprise 72% of weight of Earth’s crust

a. 45% of crust is oxygen, 27% is silicon

2. Quartz

a. SiO2 with network structure of silicon and oxygen atoms

3. Feldspars

a. aluminosilicates containing silicon, oxygen, and aluminum, combined with potassium,

sodium, and calcium

4. Mica

a. sheets of Si-O tetrahedra

b. includes muscovite (colorless, potassium and aluminum rich) and biotite (ferromagnesian)

Minerals and Rocks

c. basal cleavage

5. Ferromagnesian minerals

a. olivine

C. Other important rock-forming minerals

1. oxides

2. carbonates

a. metal ions combined with carbonate ion

3. sulfide minerals

a. metal ions combined with sulfur

4. native elements

a. minerals composed of single elements

III. Rock cycle

A. What is a rock?

1. an aggregate of one or more minerals

B. The rock cycle

1. the rock cycle is a worldwide rock-recycling system linking subsurface and surface processes

2. three main groups of rocks

a. igneous: crystallization of molten rock

C. Rock cycle and plate tectonics

IV. Three rock laws

A. Fundamental laws are required to understand Earth history

1. cross-cutting relationships

2. original horizontality

a. sedimentary layers are nearly horizontal when deposited

3. superposition

V. Igneous rocks

Chapter 3 – Instructor’s Manual

A. Definition

B. Intrusive igneous rocks

1. cool slowly and crystallize well below the surface of the Earth

3. inclusions are pieces of surrounding rock incorporated into crystallizing magma

4. batholiths and plutons

5. why magma rises and intrudes other rocks

a. probable explanation is that once formed, a mass of magma is hotter and less dense than

C. Extrusive igneous rocks

1. crystallize at surface of Earth

D. Igneous rocks and the environment

1. intrusive rocks are generally strong and resistant to weathering

2. lava flows often exhibit columnar jointing and lava tubes, both of which impart weaknesses

VI. Sedimentary rocks

A. Definitions and types

1. detrital or clastic

a. form from broken pieces of preexisting rocks

2. chemical

3. diagenesis

B. Sedimentary processes

1. sediment is delivered to sedimentary basin

3. as basin sinks or sea level rises, several kilometers of sedimentary rocks can be deposited

4. pressure of overlying rocks and precipitation of minerals from pore waters cement the rocks

C. Detrital sedimentary rocks

1. classified according to grain size

a. shale

D. Chemical sedimentary rocks

1. classified according to chemical composition

Minerals and Rocks

E. Sedimentary rocks and the environment

1. three primary environmental concerns

a. shale, mudstone, and siltstone are often very weak

VII. Metamorphic rocks

A. Definitions

1. rocks changed by heat, pressure and chemically active fluids

2. types of metamorphism

a. high-pressure, low-temperature

B. Foliated metamorphic rocks

2. types

a. slate

C. Nonfoliated metamorphic rocks

1. no alignment of mineral grains

2. types

D. Metamorphic rocks and the environment

1. foundation materials

2. foliation planes are potential planes of weakness (see Case History: St. Francis Dam)

VIII. Rock strength and deformation

A. Definition

1. resistance to failure such as fracturing, sliding, or flowing

a. varies with composition, texture, and location

B. Deformation of Earth materials

1. types of deformation

a. elastic

2. types of strength

a. compressive

b. tensile

c. shear

IX. Rock structures

A. The term “structural” refers to deformation of rocks or the resulting structures

B. Fractures

2. faults

a. displacement along fracture

3. problems associated with fractures

a. conduits for fluids

b. zones of weakness

c. fracture is subject to weathering, which widens and weakens it

C. Folds

1. form when layers are shortened by lateral compression

2. types

3. fold belts

D. Unconformities

1. definition and importance

2. types

a. nonconformity

b. angular unconformity

c. disconformity

Answers to Review Questions and Critical Thinking Questions

Review Questions

1. A mineral is a natural organic solid with characteristic chemical composition and crystalline

structure.

5. Igneous rocks form from crystallization of molten rock, sedimentary rocks form from the deposition

7. A rock is younger than any other rock it cuts.

9. A batholith is a large, regional-scale mass of intrusive igneous rock, composed of multiple plutons.

11. Detrital sedimentary rocks are composed of broken parts of preexisting rocks, while chemical

Minerals and Rocks

Critical Thinking Question

1. Steps should focus on determining the types of asbestos present and its condition, and the