All About Beaches, Islands, and Dunes

What is a Beach?  Deposits of material (sediment) that has built up –Ranges from fine sand to rocks  Occurs on coasts above the low-tide line  Wind can also influence beach development and is important in forming coastal dunes.

Sources of Beach Material  Sources of beach sediment include: –Sediments brought from rivers –Eroded materials from cliffs –Materials from the sea floor –Biological materials such as shells or coral

Shaping Beaches and Dunes  Beaches and dunes are shaped by material contintually moving on and off shore by: –Waves –Tides –wind

Beach Anatomy  Foreshore – area b/w high and low tide (sometimes covered by water, and sometimes exposed)  Nearshore – area from low tide line to sea; On the seaward side of the foreshore  Backshore – behind the foreshore. submerged only during highest tide –Includes berm – flat-topped accumulation of beach material –Beach Face: The sloping area seaward of the berm, making up most of the foreshore

 At the top end of the beach face there are sometimes a series of crescent-shaped troughs, called beach cusps.  The swash zone is the part of the beach face that is alternately covered and uncovered with water as each wave arrives.  Seaward of the swash zone, extending out to where the waves break, is the surf zone.  The shape of a beach often alters as wave energy changes over the year.

Beach Composition  The beach composition at any certain location depends on: –The material available –The energy of the arriving waves

Beach Material  Beaches are made of: –Sand  Consists of grains of minerals (quartz, granite, basalt) –Gravel –Pebbles –Fragments of living material  Shells  Skeletons of marine organisms (corals, etc.)

Wave Actions  High wave energies on beaches usually bring coarser beach material  Fine sand is usually associated with areas of lesser wave actions  Sometimes, large boulders are found on beaches, either from glacial transport, backwash from tsunamis, or rolling down from cliffs above.

Dunes  Formed by the accumulation of sand by wind blowing it off the dry parts of a beach  Develop in the area behind the backshore, which together with the upper beach face supplies the sand.  The sand used in dune formation needs to be continually replaced on the beach by waves

Saltation  The movement of sand to form dunes, usually through a jumping and bouncing motion along the ground

Dune Types  Foredune: dunes closest to shore  Primary and Secondary dune ridge: Behind them is a primary dune ridge, secondary dune ridge, and so on. These dunes are anchored and are important for the protection of beach erosion.

ORGANISMS  Most organisms living in beach or dune areas must adapt to living and burrowing in sand.  This includes crabs, worms, and insects. Shorebirds and seabirds often nest and feed in beach and dune areas as well.

All About Islands

 There are about ½ million islands in the world today.  New islands are continually popping up, while old islands are being continually eroded by wind and waves.  There are two types of islands: –1.continental islands –2.oceanic islands

Types of Islands  Continental Islands –Has split off from the main land either from:  Plates moving away  Sinking of land areas  Sea level rise  Oceanic Islands –Rise directly from the sea bed  Most are Volcanic islands

Island Biodiversity  Biodiversity is the number and types of species living in an area- islands support high biodiversity.  Endemic species are only found living in one specific place; and no where else in the world.

Island Biodiversity  Islands provide isolation, enabling species to evolve separate adaptations or species (speciation)  Endemic species have a higher risk of extinction because they are only found in one place, and are greatly affected by changes to their habitat

Madagascar has 7 out of 8 species of Baobab tree.  island of Madagascar (located off the coast of Africa) has 12,000 species of plants (80% are endemic) making it one of the riches botanical areas in the world. 90% of its reptiles are endemic, and all 66 mammal species are endemic

Island Species  The number of types of species usually decreases the farther an island is found from the mainland  The number of endemic species increases the more isolated an island is

Island Organisms  How do organisms get to islands? –They were either already living there before the land became isolated (continental islands- separating from the mainland- tectonic plate movement, sea level changes) –Ecological succession on newly formed islands: Newly formed volcanic islands, however, begin as barren areas of cooling lava. Over time, however, a grand ecological process

Ecological Succession  How do organisms get to isolated volcanic islands? –Seeds and pollen travel through the air –Eggs, larvae, or seeds get trapped in mud on birds’ feet and feathers and are carried in –Birds pass seeds through their feces –Some seeds float until they hit land (coconuts)

Island Animal Colonizers  Seals, marine birds, and turtles are the first animals to colonize an island once plants are established  Other first colonizers include animals that eat a wide range of food  Seabirds are successful on remote islands because they eat mostly fish and travel in pairs for reproduction

Island Cactus  Pioneer plants – first plants to establish an area  Cactus thrive well since their seeds can germinate in the dry lava conditions Cactus on the Galapagos Islands