Plate Boundaries and Tectonics
Constructive Plate Boundary
Where two plates diverge from each other forming a constructive margin. This is the margin where
new rocks are most likely to be found as mantle rises from the asthenosphere, solidifies forming new,
dense basaltic rock.
There are two types of divergence:
● Oceanic Areas - Sea floor spreading occurs either side of ridges in the ocean.
● Continental Areas - Stretching and collapsing of crust creates rift valleys
Eg: Great African Rift Valley
Mid-Ocean Ridges:
Are formed by oceanic divergence, includes regular breaks known as Transform faults cut across the
ridges: breaking them up. The faults occur at right angles to the plate boundary causing the
separated sections to widen at different rates. This leads to frictional stresses which build up and may
lead to shallow-focus earthquakes. Middles of ridges are marked by deep rift valleys however, the
most rapidly separating plate margin are found in the east Pacific. Volcanic eruptions along the ridge
can build new submarine volcanoes; over time these may create volcanic islands as they rise above
sea level. Eg: Ascension Island.
Rift Valleys:
Formed by continental divergence ( two continental plates) when the lithosphere stretches, causing it
to fracture.The land between these faults collapses into a deep, wide valley which are separated by
upright blocks of land called horsts. Rift valleys are widened when magma rises from the
asthenosphere, cools and solidifies to form new crust. Volcanic activity is evident due to fault lines.
Destructive Plate Boundary
When two plates meet, there are three types of convergence:
● Oceanic plate meets continental plate
Eg: Pacific Coast of South America
Constructive Plate Boundary
Where two plates diverge from each other forming a constructive margin. This is the margin where
new rocks are most likely to be found as mantle rises from the asthenosphere, solidifies forming new,
dense basaltic rock.
There are two types of divergence:
● Oceanic Areas - Sea floor spreading occurs either side of ridges in the ocean.
● Continental Areas - Stretching and collapsing of crust creates rift valleys
Eg: Great African Rift Valley
Mid-Ocean Ridges:
Are formed by oceanic divergence, includes regular breaks known as Transform faults cut across the
ridges: breaking them up. The faults occur at right angles to the plate boundary causing the
separated sections to widen at different rates. This leads to frictional stresses which build up and may
lead to shallow-focus earthquakes. Middles of ridges are marked by deep rift valleys however, the
most rapidly separating plate margin are found in the east Pacific. Volcanic eruptions along the ridge
can build new submarine volcanoes; over time these may create volcanic islands as they rise above
sea level. Eg: Ascension Island.
Rift Valleys:
Formed by continental divergence ( two continental plates) when the lithosphere stretches, causing it
to fracture.The land between these faults collapses into a deep, wide valley which are separated by
upright blocks of land called horsts. Rift valleys are widened when magma rises from the
asthenosphere, cools and solidifies to form new crust. Volcanic activity is evident due to fault lines.
Destructive Plate Boundary
When two plates meet, there are three types of convergence:
● Oceanic plate meets continental plate
Eg: Pacific Coast of South America
