At which types of tectonic plate boundaries are volcanoes most commonly found?

Introduction / Context:
This question deals with basic plate tectonics and the distribution of volcanoes on Earth. The Earths lithosphere is broken into moving plates, and interactions along plate boundaries create earthquakes, mountains, and volcanic activity. Different types of boundaries produce different geological features. The question asks at which types of tectonic boundaries volcanoes commonly occur.

Given Data / Assumptions:

• The key terms are convergent plate boundaries and divergent plate boundaries.
• Destructive boundaries are another name often used for certain convergent boundaries where oceanic crust is subducted.
• The options include convergent only, divergent only, both, or destructive only.
• We assume a basic model of tectonic plates and magma generation.

Concept / Approach:
Volcanoes commonly occur in two main plate boundary settings. At convergent boundaries, especially where an oceanic plate is subducted beneath another plate, melting occurs in the mantle and magma rises to form volcanic arcs, such as the Pacific Ring of Fire. At divergent boundaries, such as mid ocean ridges or rift zones, plates move apart and magma rises to fill the gap, creating new crust and volcanic activity. Therefore, both convergent and divergent boundaries are associated with volcanoes. Transform boundaries, where plates slide past each other, have earthquakes but usually not volcanoes.

Step-by-Step Solution:
Step 1: Recall that convergent boundaries involve plates moving toward each other, often with one plate subducting beneath another. Step 2: Understand that subduction at convergent boundaries leads to melting of mantle material and formation of magma, which rises and can form volcanoes. Step 3: Recall that divergent boundaries involve plates moving away from each other, as seen at mid ocean ridges where magma reaches the surface to create new oceanic crust. Step 4: Recognise that at both convergent subduction zones and divergent spreading centres, magma is generated and can reach the surface as volcanic eruptions. Step 5: Therefore, volcanoes are common at both convergent and divergent boundaries, so option C is correct.

Verification / Alternative check:
To verify, think of real world examples. The Andes and the Japanese island arc are classic convergent boundary volcano chains where an oceanic plate is subducted beneath a continental or island arc plate. The Mid Atlantic Ridge and East African Rift are examples of divergent boundaries with volcanic activity. Together, these examples show that volcanoes occur in both settings. Destructive boundaries is another term for certain convergent boundaries, but the question asks whether volcanoes occur at only one type or at more than one type of boundary.

Why Other Options Are Wrong:
Option A, convergent boundaries only, ignores volcanic activity at divergent boundaries such as mid ocean ridges. Option B, divergent boundaries only, overlooks the large number of volcanoes at subduction zones, which form some of the most active volcanic belts on Earth. Option D, destructive boundaries only, is similar to option A and still omits divergent settings. Thus, all of these options are incomplete descriptions of where volcanoes occur.

Common Pitfalls:
A frequent error is to memorise one prominent example, such as the Pacific Ring of Fire, and conclude that volcanoes occur only at subduction zones. Another pitfall is to overlook underwater volcanic activity along mid ocean ridges, because it is less visible on land. To avoid these mistakes, remember that volcanoes are common wherever plates either collide with subduction or move apart, but are rare where plates simply slide past one another without major vertical motion.

Final Answer:
Volcanoes commonly occur at both convergent and divergent plate boundaries.