Final answer:
The Great Pacific Garbage Patch (GPGP) is primarily formed by garbage produced on land that is carried into the ocean through runoff and the patterns of ocean currents that create circular gyres where floating materials accumulate.
Step-by-step explanation:
The factors that have contributed to the formation of the Great Pacific Garbage Patch (GPGP) are:
- Garbage produced on land: Trash and waste generated on land are carried by rivers and brought into the oceans through runoff.
- The patterns of ocean currents: The GPGP is formed due to the convergence of ocean currents that create circular gyres in which floating materials accumulate.