Fig. 1.10 Divergent (constructive) plate boundary – the formation of the Mid-Atlantic Ridge.
NORTH AMERICA
EXAM TIP (OL)
With the exception of 2014, a question on the ‘formation of landforms’ appeared every year from 2011 to 2018.
Marking Scheme:
Landform named = 3 marks
Example = 2 marks
Description of its formation = 5 SRPs × 3 marks
Continental splitting
Rising magma plumes have caused the continental African crust to stretch and split. Magma rises through fissures in the crust forming volcanoes (new crust) on the earth’s surface such as Mount Kilimanjaro in an area known as the East African Rift Valley.
A-Z
Fault lines: Fractures on the earth’s surface where rocks on either side of the crack slide past one another.
Transform plate boundary: This type of boundary can also be referred to as a ‘conservative’ or ‘passive’ plate boundary.
Transform plate boundaries
Transform plate boundaries occur where two plates slide past one another. While land is neither created nor destroyed, rocks at the edge of both plates can lock in position. Stress builds up at the boundary as convection currents continue pushing the plates laterally past each other. Earthquakes are generated when rocks at the boundary eventually break, allowing the plates to move forward very suddenly.
Along the San Andreas Fault line, the Pacific and North American plates are both moving north-west, but at different speeds (Fig. 1.11). Earthquakes occurring here are particularly violent, as the focus of the quake tends to be close to the surface of the earth’s crust.
Mid-Atlantic Ridge (new oceanic crust)
Volcanic island (Iceland)
EUROPE
Convection currents
Mantle Rising magma
Convection currents
San Francisco San Andreas Fault
PACIFIC PLATE
Fig. 1.11 Transform plate boundary – the Pacific and North American plates slide past one another.
