Folding and Faulting

Question 1

Tectonic forces that change the rock structure on the earth

Answer 1

TENSION, COMPRESSION, SHEARING

Question 2

Tension

Answer 2

Plates separate and lengthen or stretch and break apart

Question 3

Compression

Answer 3

Plates collide, rocks are squeezed and shortened causing them to fold or fracture

Question 4

Shearing

Answer 4

Plates slide past eachother

Question 5

Process of folded structures

Answer 5

Continental plate is compressed by forces acting on both sides, flat body of rock buckles, doesn’t fracture due to flexibility of plates and time scale (long time)

Question 6

Anticline

Answer 6

Layers of rock that fold upwards

Question 7

Syncline

Answer 7

Layers of rock that fold downwards

Question 8

Limb

Answer 8

Sides of the fold that join anticline and syncline

Question 9

Symmetrical fold

Answer 9

Limbs on each side are the same in length and steepness

Question 10

Asymmetrical fold

Answer 10

Limbs on either side are different in length/steepness

Question 11

Overfold

Answer 11

One limb pushes over the top of the other

Question 12

Recumbent fold

Answer 12

When both limbs are moving in same direction causing large overhang

Question 13

Orogeny

Answer 13

Mountain building period caused by folding and faulting e.g Caledonian

Question 14

Trend

Answer 14

General direction in which something is developing

Question 15

Denudation

Answer 15

The breakdown of rock by weathering or erosion

Question 16

Caledonian folding

Answer 16

• 400M years ago
• Ocean floor subducted and sea floor buckled up
• Magma intruded into gaps in unfolds to form igneous rocks and metamorphic rocks
• Large crystals formed
• ORIGINALLY higher than any other

Question 17

Armorican Folding

Answer 17

• 250 million yrs ago
• East to west directional trend
• Never reached the height of Caledonian folding
• Caha Mountains or Comeraghs

Question 18

Alpine folding

Answer 18

• Reached peak 30M years ago
• Subduction didn’t occur
• Current highest mountains

Question 19

Faulted Structures

Answer 19

Compression, tension leads to fractures and weakness, strata displaced at fault line

Question 20

Case study: East African Rift Valley

Answer 20

• 20M yrs ago
• 4,800km from Syria to Zambezi river
• Magma plume caused continent to bulge
• Rift valley formed
• Subsided land is 153m below sea level
• Widens at 4mm per year
• Eventual split of plate
• Mt. Kilimanjaro formed due to Magma rising through weakness in rock

Question 21

Faults resulting from compression
- Reverse Fault

Answer 21

Forms at convergent plate boundaries when compression in the earth’s crust causes fractures.

Question 22

Compression: Thrust Fault

Answer 22

Found in areas where one plate is being subducted under another, fault at 45° or less

Question 23

Compression: Block Mountain or Horst

Answer 23

Compression creates two parallel faults and a large block of land between faults gets pushed upwards.

Question 24

Shearing: Tear Fault

Answer 24

Occurs at transform boundaries where rocks at edge of plate can lock. Earthquakes can occur

Question 25

Others: Dome structures

Answer 25

Layers of rock arch upwards to form a circular structure called a dome. This happens when a compressional force is exerted on a plate, or when rising magma raises rock upwards. E.g Slieve Blooms

Question 26

Other: Horizontal Structures

Answer 26

Uplifted without any tilting, folding or faulting. Can be easily seen in sedimentary rocks e.g loop head

Question 27

Other: Uniclinal Structures

Answer 27

Uplifted on one side and not the other e.g Ben Bulben