Here's why:

* Oceanic portion: The majority of the Caribbean Plate is made up of oceanic crust, which is denser and thinner than continental crust. This oceanic crust forms the floor of the Caribbean Sea.

* Continental portion: The plate also includes portions of continental crust, specifically the islands of Cuba, Hispaniola, Jamaica, Puerto Rico, and others. These islands are formed from continental fragments that have been accreted to the plate over time.

Therefore, the Caribbean Plate is considered a mixed plate, containing both oceanic and continental crust.