To accumulate is to gather or for things to come to you.
the deposition or accumulation of sediment
A disorderly or dirty accumulation, heap, or jumble
'Hoard' means a hidden accumulation. So hoarded would mean that you have accumulated certain items and hidden them.
A slowly moving mass or river of ice formed by the accumulation and compaction of snow on mountains or near the poles.
The definition of accumulation are the following; A gradual gathering of something like dirt or dust, acquisition of something. One can also better understand it by its synonyms such as collection, heap and pile.
In the Wikipedia definition it is not technically in the classic sense. The Keys are not "tectonic" in nature, but a natural formation of coral and the accumulation of vegetation and sand. Wiki says that the classic definition has now been expanded to include any accumulation of islands, especially those clusters close to main bodies of land. So in today's definition, yes, the Keys are an archipelago.
As a noun the word 'conchal' refers to a shell like structure that is made from accumulation of marine invertebrates. The structure is usually found on beaches.
separation of power
A parasitic cone (or satellite cone) is the cone-shaped accumulation of volcanic material created by eruptions from fractures other than the central vent of a volcano.
Capital formation is essentially a term used to describe a company or governments total accumulation of funds in an accounting year. This is commonly practiced in many businesses.
Recycle stream is a process in which a portion of the output stream is returned to the input stream for further processing. Purge stream is the removal of a portion of the output stream to prevent accumulation of impurities or by-products in the system.
Accumulation is a noun - the act of accumulating