Answer: South American plate and African plate
Explanation: Tristan de cunha is a volcano that has formed approximately 150 million years back when the plates namely, the African plate and the South American plate moved in the opposite direction. Due to this diverging plate motion, the Atlantic ocean was formed.
Tristan de cunha is a stratovolcano, having a total height of about 6000 m, of which, about 4000 m lies below the sea level and 2000 m lies above the sea level. It is located at about 500 km towards east of the Mid-Atlantic ridge. The volcano is surrounded by the lava flows and pyroclastic rocks that must have erupted from the volcano in the past.