3.1.5.2 Plate tectonics

Question 1

Define a subduction zone

Answer 1

When two tectonic plates converge and the older, denser plate is subducted under.

Question 2

Name the zone where the subducted plate begins to melt

Answer 2

Benioff zone

Question 3

Define island arcs

Answer 3

• form during subduction where the subducting plate begins to melt and plutons of magma bubble to the surface
• if these happen offshore then a line of volcanic islands, known as island arcs, form

Question 4

Provide an example of island arcs

Answer 4

Mariana islands

Question 5

Define ocean ridges

Answer 5

Formed at oceanic constructive plate boundaries where basaltic lava forms a ridge

Question 6

Define rift valleys

Answer 6

Formed on continental constructive plate margins where crust can drop to a variety of levels

Question 7

Provide an example of a conservative plate boundary

Answer 7

San Andreas fault

Question 8

Type of magma on constructive and destructive plate boundaries

Answer 8

• basalt on constructive plate margins
• rhyolite on destructive margins

Question 9

Characteristics of lava on plate margins

Answer 9

• runny, low viscosity on constructive
• high viscosity on destructive