The accumulation of windblown sand marks the beginning of one of nature's most interesting and beautiful phenomena. Sand dunes occur throughout the world, from coastal and lakeshore plains to arid desert regions. In addition to the remarkable structure and patterns of sand dunes, they also provide habitats for a variety of life which is marvelously adapted to this unique environment. Picturesque dunes against a sky of blue or a full moon, with perfectly contoured shadows of ripples and undulating crests, have always been a favorite subject of photographers. Dunes have also been the subject of many desert movies, and have historically been a formidable barrier to vehicular and rail travel. Depending upon one's particular situation, they can be one of the most incredibly beautiful, thrilling, eerie, treacherous or just plain inhospitable places on earth.
Good Post Jilly. When we are at the beach enjoying all it's benefits we should realize there is an entire ecosystem thriving there.
Plants play an important role in building sand dunes. Swales between ridges are low-lying depressions. Farther from the ocean, plants thicken into shrubs and maritime forests, which are old dunes rooted in place by vegetation.
Check out this short video: http://tiny.cc/0Jbb1
Beaches and recreation
Beaches have long been a popular attraction for tourism and recreation. Especially popular are seaside resorts and large white sand beaches. Of course, residents and tourists alike use beaches as a place for leisure and sport. The relatively soft formation of sand is comfortable to sit or lie on, and entering and exiting the water is far easier across a sand beach than a rocky shore. The waves present at beaches add to the enjoyment and make the sport of body surfing and related activities possible. One of the many attractions of a sand beach, especially for children, is playing with the sand, building sand castles and other constructs.
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A beach is a popular form of recreational "park"; here, Sunset Beach Park on O'ahu
Towels and mats are typical beach "furniture". In the Victorian era, many popular beach resorts were equipped with bathing machines because even the all-covering beachware of the period was considered immodest. This social standard still prevails in some Muslim countries. At the other extreme are nudist beaches, where swimware of any kind is discouraged.
The most common constituent of sand, in inland continental settings and non-tropical coastal settings, is silica (silicon dioxide, or SiO2), usually in the form of quartz, which, because of its chemical inertness and considerable hardness, is the most common mineral resistant to weathering.
The composition of sand is highly variable, depending on the local rock sources and conditions. The bright white sands found in tropical and subtropical coastal settings are eroded limestone and may contain coral and shell fragments in addition to other organic or organically derived fragmental material. The gypsum sand dunes of the White Sands National Monument in New Mexico are famous for their bright, white color. Arkose is a sand or sandstone with considerable feldspar content, derived from the weathering and erosion of a (usually nearby) granitic rock outcrop. Some sands contain magnetite, chlorite, glauconite or gypsum. Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts and obsidian. Chlorite-glauconite bearing sands are typically green in color, as are sands derived from basaltic (lava) with a high olivine content. Many sands, especially those found extensively in Southern Europe, have iron impurities within the quartz crystals of the sand, giving a deep yellow color. Sand deposits in some areas contain garnets and other resistant minerals, including some small gemstones.
Sand is transported by wind and water and deposited in the form of beaches, dunes, sand spits, sand bars and related features.
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.
As the term is used by geologists, sand particles range in diameter from 0.0625 (or 1⁄16 mm, or 62.5 micrometers) to 2 millimeters. An individual particle in this range size is termed a sand grain. The next smaller size class in geology is silt: particles smaller than 0.0625 mm down to 0.004 mm in diameter. The next larger size class above sand is gravel, with particles ranging from 2 mm up to 64 mm (see particle size for standards in use). Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like flour).
ISO 14688 grades sands as fine, medium and coarse with ranges 0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm. In USA, sand is commonly divided into five sub-categories based on size: very fine sand (1⁄16 - 1⁄8 mm diameter), fine sand (1⁄8 mm - 1⁄4 mm), medium sand (1⁄4 mm - 1⁄2 mm), coarse sand (1⁄2 mm - 1 mm), and very coarse sand (1 mm - 2 mm). These sizes are based on the Krumbein phi scale, where size in Φ = -log base 2 of size in mm. On this scale, for sand the value of Φ varies from -1 to +4, with the divisions between sub-categories at whole numbers.
What is a sea urchin? Heart urchins and cake urchins are just some of the many species of sea urchins. These unusual animals provide an endless source of fascination. They are closely related to sea stars, sharing the same five-fold symmetry, and they too move about on hundreds of hydraulically operated tube feet. Sea stars and sea urchins are from a group known as echinoderms, a word meaning ‘spiny skins’. Sea urchin eggs have properties that make them important for medical research. Compounds extracted from marine organisms are initially tested to see whether they inhibit the production of rapidly dividing sea urchin eggs. If so, they may have potential to provide cures for AIDS, cancer and other diseases.
What do they look like? Regular urchins are spherical animals with a case or shell of close-fitting limy plates. Sea urchins have spines that protect them from predators. However, it is mostly the hard outer shell, from which the spines have usually broken off, that is found washed up on beaches.
Where do they live? Sea urchins are found in all of Western Australia's marine parks. They are most common in intertidal habitats and on shallow reefs, but have been found as deep as 7000 metres.
What they eat and how: They feed on kelp and other kinds of seaweeds. Due to their ability to reproduce rapidly when conditions become favourable, they can reach plague proportions, only to die in huge numbers when they eat out their food source.
Threats: In other parts of the world, people are one of their main predators. In some parts of the world, sea urchins are believed to be powerful aphrodisiacs. The roe is a prized delicacy in Japan, in islands of the Pacific and in European countries such as France, Italy and Greece.
Behaviour: They use the spines on the underside to move around, making them look like they are walking on stilts. Some tropical species, such as the flower urchin, have venom-tipped spines that can cause severe pain to careless divers.
Conservation status: Sea urchins are very common all around the Western Australian coast.
This post was modified from its original form on 27 Jul, 9:49
Hope you don't mind but I see a ton of posts just for graphics and I think its also important to understand the things at the beach that we love so much too. If not please delete this post, no worries.
