Introduction:
Volcanic activity is indeed common in areas around marine trenches. This phenomenon can be attributed to several factors that are closely related to the geological processes occurring in these regions. The interaction between tectonic plates, subduction zones, and the presence of magma chambers are key factors contributing to volcanic activity in areas around marine trenches.

1. Tectonic Plate Interaction:
The Earth's lithosphere is divided into several large plates that are constantly moving. At certain boundaries where these plates interact, volcanic activity tends to occur. Marine trenches are primarily located at convergent plate boundaries, where two plates are colliding or moving towards each other. These boundaries are known as subduction zones.

2. Subduction Zone:
Subduction zones are areas where one tectonic plate is forced beneath another. In the case of marine trenches, oceanic plates are usually subducting beneath continental plates. As the oceanic plate descends into the mantle, it undergoes intense heat and pressure. This process causes the release of water and other volatile substances from the subducting plate, leading to the formation of magma.

3. Magma Formation:
As the subducting plate sinks deeper into the mantle, the increase in temperature causes the release of water and other volatiles trapped within the plate. These volatiles lower the melting point of the surrounding mantle rocks, resulting in the formation of magma. The magma then rises through the overlying mantle and accumulates in magma chambers, which are often located beneath volcanic arcs associated with marine trenches.

4. Volcanic Arcs:
Volcanic arcs are chains of volcanoes that form above subduction zones. They are characterized by a string of stratovolcanoes, which are cone-shaped volcanoes composed of layers of solidified lava, ash, and other volcanic materials. The presence of magma chambers beneath volcanic arcs is a significant factor contributing to volcanic activity in areas around marine trenches.

Conclusion:
In conclusion, volcanic activity is common in areas around marine trenches due to the interaction between tectonic plates, the formation of subduction zones, and the presence of magma chambers. The convergence of oceanic and continental plates at these boundaries creates the conditions necessary for the formation of magma, which ultimately leads to volcanic eruptions. Understanding these geological processes is crucial for studying and predicting volcanic activity in these regions and ensuring the safety of nearby populations.

The surface as sea-floor spreading causes plates to move apart and new crust is formed by magma pushing up from the mantle. Because the 75 Percent of the world's volcanoes are all present in the Pacific ring of fire...and there are a number of marine trenches present in the Pacific ring of fire