Folding and Faulting definitions Flashcards
Alpine folding
The youngest period of mountain building that occured about 50 million years ago. Still active today. Alpine mountains include the Alps, Himalayas, Andes, Rockies and Atlas Mts
Anticline
An up fold of a rock layer
Asymmetric fold
A fold in which the limbs are unequal in length and the axial plane is tilted to one side
Armorican folding
A long period of mountain building that occured about 300 million years ago. The trend of mountain ranges runs from East to West
Block Mountain/horst
A mountain formed by the uplift of a block of rock between 2 faults
Caledonian folding
The oldest period of mountain building that occurred about 400 million years ago. The mountains trend from North-east to South-west
Fault
A crack in a rock along which the ground moves
Fault scarp
A cliff or steep slope formed hen ground is uplifted or sinks along a fault in the earths crust
Fold
A bend in a layer of rock
Geosynclines
A huge long hollow in the earths crust into which thick layers of sediment are deposited
Normal fault
A fault where the hanging wall has moved downward relative to the footwall of a fault. Normal faults are caused by 2 blocks of rock being pulled apart
Old Red Sandstone
Thick sequence of rocks (formed 300-400 million y.a) that formed from sediments originating on land. Found in the north-western Europe, Scandinavia, Greenland and Canada
Orogeny
A period of mountain building caused by colliding plates
Overfold/recumbent fold
This fold has one limb pushed over the other limb, until the axis of the fold is almost horizontal and the two limbs are almost parallel. This is formed when pressure from one side is much greater than from the other side
Overthrust fold
A type of overfold where the forces of compression are so great that the fold breaks and the overlying limb moves over the limb below
Plate compression
When 2 plates collide
Reverse fault
A fault in which the hanging wall moves upward relative to the footwall. They are formed by 2 blocks of rock being pushed together
Rift valley/graben
A valley formed when a block of land sinks between 2 parallel faults
Symmetric fold
This type of fold has 2 limbs of equal steepnedd. It results when the 2 oppsoing forces moving towards each other are of equal strength. The fold axis is vertical.
Syncline
A down fold in a layer of rock
Tear/transform fault
A fault where 2 blocks of rock move sideways relative to each other
Tension
A force pulling rocks apart
Thrust fold
A low angle fault
Trend
The direction along the crest of a fold
