Fig. 51. Three types of fault motion

EXERCISES

1. Match the English term with the Russian variant. (TEXT: Fault terminology)

2. Re-read the text “Fault terminology”. Look at the diagram (anatomy of a fault). Label the letters and give an explanation.(R.P – 8.3.1.2)

Match the term with its definition and then find its translation.

4 Fill in the gaps with the missing words.

A fault is a (1) _______________ along which one side has moved (2)_____________ to the other. The term fault is generally used for (3)___________ fractures. A fault divides a rock into two (4)________________. The bottom surface of the upper block is the (5)____________, and the top surface is the (6)_________________. Faults are classified in terms of the (7)_________________ of the fault surface. The fault dip may be more than (8)_______________, which is called (9)______________. If it is less than (10) __________, it is a (11)____________. A fault can be divided depending on the (12)___________ of the (13)__________. Also they are subdivided on terms of (14) ____________. Faults may also be either (15) ________ ( ) or (16)___________ ( ).

5 Read the following fault types. The look at the diagrams and then try to draw them by heart. and draw a diagram. (R.P – 8.3.1.3, 8.3.1.4)

1.Normal fault – stretching breaks rocks along

a steep fault plane, and one block drops or rises

against the other.

2. Reverse fault – compression forces one block

up and over another. A thrust fault is a reverse fault

with a low-angled fault plane producing great

horizontal movement.

3. Tear(strike-slip, transcurrent, wrench)fault –

horizontal shearing along a vertical fault plane.

Transform faults are tear faults at right angles

to oceanic ridges.

4. Graben-a long, narrow block sunk between

two parallel faults.

5. Horst- a horizontal block raised between

two normal faults

Fig. 52. Fault types

6. Here are six definitions. Read the definition, then name the term and give its translation (R.P – 8.3.1.3, 8.3.1.4)

1. horizontal block raised between two normal faults

2. a long, narrow block sunk between two parallel faults

3. one block drops / rises against the other

4. horizontal shearing along a vertical fault plane

5. an uplifted, tilted block

6. one block is forced up and over another

LISTENING COMPREHENSION

You will hear part of a lecture. For statements 1-14, give the correct answer according to what the speaker says. You will need to write a word or short phrase.

1. What is another term for splits formed in stressed rocks?

2. What is a joint?

3. How do joints form?

4. Where do joints occur?

5. What are faults?

6. What explains the weakness in the Earth’s crust?

7. What does block faulting create?

8. How many types of faults are there?

9. What are the main types of faults?

10. When does a normal fault occur?

11. How is a reverse fault formed?

12. What forces create reverse faults?

13. What is an example of a tear fault?

14. What is the difference between graben and horst?

COMPREHENSION: FOLDS

VOCABULARY

WORD FORMATION

VERBS (+ PREPOSITION)

to drape over – ниспадать складками;

to precede – предшествовать;

to manifest – проявляться, становиться явным;

adjacent to – смежный, расположенный рядом;

to converge upon – стремиться к пределу;

to associate with – связывать с, ассоциировать с.

Fold terminology (R.P. - 8.3.2.1, 8.3.2.3)

Folding in layered rocks consists of deformation of strata without faulting. Folds are formed by compression, draping over basement blocks, and compaction. Faulting often accompanies folding and can precede it or follow it. The triaxial stress system for folding is representative for faulting since the two are intimately related.

Folds are manifested as different types according to morphology, origin and type of internal deformation. General fold terminology is descriptive and relates to elements of individual features applicable to all types of folds

1. Anticline is a fold with upward convexity. Beds that make up an anticline dip in opposite directions away from the crest or high point of the fold.

2. Syncline is a concave upward. Beds making up a syncline dip in opposite directions toward the trough, or low point of the fold.

3. The hinge point occurs at the locus of maximum curvature of a fold. The hinge point is applicable equally to anticlines and synclines. Hinge points connected on any particular bedding surface are joined along a hinge line.

4. The locus of all hinge lines of a fold is the hinge surface of the fold.

5. An inflection point occurs where bed curvature in one direction changes to bed curvature in the opposite direction. Inflection occurs where concavity changes to convexity.

6. The limbs or flanks of folds are those portions adjacent to the inflection lines of folds. They converge upon the inflection line synclines and diverge from it in anticlines.

7. A fold is symmetrical when its shape and mirror image are identical or when the fold is bilaterally symmetrical about the hinge surface. Symmetrical folds are usually represented by a vertical hinge surface.

8. A fold that is not bilaterally symmetrical about the hinge surface is asymmetrical. Its hinge surface is usually inclined.

(Абрамова Р.Н., Квеско Н.Г., Introduction to Continuum Mechanics- учебное пособие, Томск, ТПУ. 2005.)

Fig. 53. Fold terminology

Fig. 54. Folding structure

EXERCISES

1. Take a piece of paper. Fold it like a fan. What does it look like? Does it show the geometric parts of a fold?

2. Read the definitions and draw the corresponding folds and label them. (R.P 8.3.2.2)

1. Rock beds are folded into an arch;

arch from a few feet to many miles across;

2. Downfolded sedimentary rock layers that

form a basin. Immense synclines are called

geosynclines.

3. Its shape and mirror image are identical; a vertical

hinge surface.

4. Hinge surface is usually inclined.

5. Both limbs and the axial plane dip in the same direction

LISTENING COMPREHENSION