Transform margins

Question 1

Transform margins =

Answer 1

Where ridges/subduction zones terminate horizontally

Can be oceanic and continental

N.B. Transform evolution

Question 2

Ridge-ridge transforms

Answer 2

Hot, buoyant material at ridge = shallow bathymetry/topographic high

Further away from ridge = cools and subside

SCARP

Intersection highs

Question 3

Ridge-ridge transforms: scarp =

Answer 3

Difference in elevation across a fault

FAST SPREADING TRANSFORMS

• two points of same age more likely to be closer than for slow spreading
• = more gentle scarp

SLOW SPREADING TRANSFORMS
- greater difference in age = more steep

Question 4

Ridge-ridge transforms: intersection highs

Answer 4

Anomalous areas of high topography due to:

1. Underwater volcanism
   - oozes and builds up
2. Conductive heat transfer from ridge
   = buoyant
3. Magmatic/hot material moving underneath lithosphere
   = upwelling

Question 5

Continental transforms

Answer 5

Tend to follow old lines of weakness/branch around harder areas
= broad zones of (mostly) strike-slip deformation

Question 6

Continental transforms: releasing bends

Answer 6

E.g. Dead Sea

Left-stepping offset along a sinistral fault
= extension
= normal faulting
= rifting
= depression

Question 7

Continental transforms: restraining bends

Answer 7

E.g. San Andreas

Left-stepping offset along a dextral fault
= compression
= reverse faulting
= topographic high

Question 8

Seismicity

Answer 8

Shallow, strike-slip motions

e.g. Romanche Transform, offsets Mid Atlantic Ridge by 900km, centroid depths between 7-20km