Sediment cores reveal that the Thousand Islands were formed when a storm-driven sea broke through the barrier island, leaving behind an approximately flood tide delta deposit. The date of this event is unknown. Charts from the mid 19th century and older do not depict the Thousand Islands. However, this might be due to lack of detail. The Cocoa Beach area was surveyed in 1876-1877 and appears identical to the 1951 aerial photographs. The stratigraphic characteristics of a flood tide delta deposit include the existence of a layer of plain sand (often containing terrestrial vegetation debris) sandwiched between sediments containing numerous small
bivalve mollusc shells that are indicative of deposition in a normal lagoon environment. This uneven sand layer lacking shells suggests an interruption in the normal accretion of
benthic sediments by a rapid deposition of dune material being washed in by severe wave action. There are about 100 islands in the Thousand Islands, The actual number of islands is meaningless due to the inundation of many areas during seasonal high water during summer. The relatively low topography and rising water levels can turn one island into many as rains begin. The Thousand Islands are divided roughly in half by the Minutemen Causeway. The formation comprises approximately of salt marsh, mangroves,
spoil sites containing upland vegetation, and maritime
hammocks on shell
middens. Beginning in the late 1950s, small ditches were dug through the islands to allow water movement and fish access to inner areas of the succulent marsh for
mosquito control. At approximately the same time, dredge and fill activities were begun in Cocoa Beach for housing development. Developers dredged canals and used the spoil to provide fill material for houses. Several areas of the Thousand Islands were filled but not fully developed, leaving large areas of uplands. During the late 1960s Brevard County Mosquito Control began dredging the Thousand Islands south of Minutemen Causeway, resulting in conversion of
salt marsh to upland dredge spoil with the state-owned
C-34 impoundment. ==Flora==