Tectonic Plates

Fiji is located at the Indo-Australian and the Pacific plate boundary. As a result, Fiji is considered to be on the Pacific ring of fire with countries such as Argentina, Brazil, Guatemala, etc. Due to this feature of two plate boundaries, Fiji finds itself in the midst of two opposite facing subduction zones which lead to the formation of volcanoes and the threat of earthquakes.

Also, Fiji's tectonic history cannot be explained equally but instead into two separate stages. Stage one: 40-28 million years ago is defined by the continuous volcanic island arc system, known as the Vitayaz Arc. The arc was formed by subduction of the Pacific plate under the Indo—Australian plate. Stage two: 28-12 Million years ago was defined by the diagonal north subduction of the Pacific plate under the Indo—Australian plate. Subduction was therefore a particularly shallow angle to the plate boundary. This all essentially means Fiji was caught under a period of increased stress on the tectonic plates which only increased the uplift of volcanic rocks and formations across the islands. 

This is what the subduction zone Fiji finds itself in is like.

As you may see through the map key, Fiji lies in between the Indo-Australian plate and Pacific plate in a subduction zone. 


Sources: 
Link to article: http://www.mrd.gov.fj/images/Brochures/Plate_Tectonic.pdf
Link to first image: https://study.com/academy/lesson/convergent-boundary-definition-facts-examples.html
Link to second image:http://www.mrd.gov.fj/images/Brochures/Plate_Tectonic.pdf