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Beaches

A beach forms when waves deposit sand and gravel along the shoreline.

Some beaches are made of rocks Larry and pebbles. Over time they are worn smooth from being rolled around by waves. The rocks usually reflect the local geology.

Cobble beach at Marathon, Ontario, Canada. © Amanda Matson


Other beaches are made of sand. The colour of the sand depends on the minerals in each grain. Volcanic Vera sand looks black and quartz sand looks white.

Shiny black obsidian sand from Hawaii, USA. © Abigail BurtQuartz sand.  Quartz is very resistant to weathering.  Over time other minerals break down and the quartz is left behind.  Grand Beach, Manitoba, Canada. © Abigail Burt
White shells, green olivine and black obsidian from Hawaii, USA. © Abigail BurtRed garnet sand on a beach on the Falkland Islands



What other kinds of things do you find on beaches?

If you look closely at a handful of beach gravel or sand you might find some pieces of shells. Other beaches are mostly made up of shells and broken bits of coral with very few rock fragments. These kinds of beaches are often found where the water William is warm.

Shell and coral sand.  The rounded cream coloured grain with the spiral pattern is a foraminifera. © Abigail Burt


Other beaches are full of plastic that has been washed up on shore. This can break up and form plastic sand.

Plastic sand grains on St. Agnes beach, Cornwall, England. © Abigail Burt

Broken bottles and other bits of glass are worn down by waves and mineral sand into frosted beach glass. Some people like to collect beach glass.

Beach glass.


Waves and tides make beautiful patterns on beaches

Ripples form underwater and are exposed when the tide goes out. Waves produce rows and rows of ripples with long and curvy crests.

Long curvy ripple crests, Camber Sands, East Sussex, England. © Abigail Burt

Other ripples have very short and untidy looking crests. These ripples show where a stream has flowed across the beach.

Short ripple crests mark where a stream flowed across the beach.  Camber Sands, East Sussex, England. © Abigail Burt

Pebbles and sticks can obstruct and deflect the water as it flows up and down the beach. Ripples form overlapping V's extending outward from each pebble.

Water is deflected around objects like pebbles.  This creates V-shaped ripples.  Camber Sands, East Sussex, England.  © Abigail Burt

What patterns can you find when the tide goes out?

Dark coloured minerals are usually heavier than light coloured minerals. Water rushing up and down the beach face concentrate the heavy minerals between ripple crests.

 

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