from the beach at Ramsay Bay. Hinchinbrook Island is made up of late
Palaeozoic igneous rocks. The main
pluton in the east of the island, the Hinchinbrook Granite, is composed of various
hypersolvus granites and
intrudes volcanics,
granodiorites, and
granites. The island and coastal ranges are thought to have been thrust up as blocks with subsidence between them to form the coastal plain with the summit level of the island being an older dissected surface that has been uplifted to approximately or more
above sea level. The
Hinchinbrook Channel that separates the island from the mainland is considered to be
fault controlled. Since the last Ice Age 18,000 years ago sea level has risen. Once there was a significant rugged coastal range, now there is Hinchinbrook Island. To the west is the
mangrove-fringed Hinchinbrook Channel with of robust mangrove estuaries. The channel is the valley of the
Herbert River flooded following the
last glacial period. The island is only separated from the mainland at times of high sea-level such as the present and is thought to have had dry land connections to the mainland for most of the past few million years. Further west is the Cardwell Range Escarpment rainforest. East of Hinchinbrook Island lies the
Coral Sea, Great Barrier Reef Lagoon and
Great Barrier Reef. To the north of Hinchinbrook Island,
Rockingham Bay hosts densely vegetated continental islands, e.g., Garden Island,
Goold Island,
Brook Islands Group,
Family Island Group,
Bedarra Island and
Dunk Island east of
Mission Beach. South of Hinchinbrook Island, the Cardwell Range gives way to the Herbert River floodplain and delta. Missionary Bay is at the northern end of Hinchinbrook Island National Park. Natural features of this biodiverse area include of dense
mangrove communities lining the shoreline. A shallow subhorizontal tidal zone has extensive offshore
sea grass beds grazed by
dugong. The
beach stone-curlew thrives on the island, unlike on mainland beaches because vehicles are banned. The barrier, which consists mainly of
aeolian sands, extends more than below the present sea level in places. It is thought to have been formed in two major episodes, the older dunes being partly drowned during an early
Holocene marine transgression (9500–6000
C-14 years BP) with the later generation of dunes forming within the last 900 C-14 years BP. Hinchinbrook Island is described as a "wilderness area," wild and rugged with soaring mountainous peaks. Hinchinbrook Island's highest mountain is
Mount Bowen,
above sea level. Other notable mountain summits are
The Thumb (),
Mount Diamantina () and
Mount Straloch (). Terrestrial vegetation types include thick
shrubs,
heath,
bushland and
forest. The island habitat provides refuge for numerous
endangered species, both flora and fauna such as the
giant tree frog. The local climate is tropical, warm to mildly cool and dry during the winter months. The summer monsoon wet is warm to hot and humid, coinciding with the tropical cyclone season. The island has no reefs in the waters surrounding it, most likely due to fresh water runoff from the island. ==History==