How much do you know about the beach?

beautiful beach with waves hitting the shore
Photo: Berit Watkin/flickr

You go to the beach to relax, to walk and to soak up the sun. But how much do you really know about the waves, the sand and unique traits about beaches around the globe?

Question 1 of 15

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a blanket of seashells on the beach
Photo: Jeremy T. Hetzel /flickr
Where is the top U.S. beach for finding seashells?

Often called the best shelling spot in North America, Sanibel's beaches are protected by a broad underwater shelf. The buffer helps shell-laden currents gently lay their deposit on the sand. The island's unusual east-west orientation acts like a shovel, scooping shells up onto the shore.

Question 2 of 15

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turtle on a black sand beach
Photo: Steve Cadman/flickr
Why are black sand beaches black?

The dark grains on black sand beaches are actually tiny shreds of basalt or volcanic rock, formed when lava from nearby volcanoes cools. Some of the most famous black sand beaches are in Hawaii, but they're also found in the Caribbean, South Pacific and Iceland.

Question 3 of 15

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ocean waves
Photo: Carlos Castro/flickr
What causes most ocean waves?

When wind transfers its energy to the water, waves are formed. The size of a wave depends on wind speed, wind duration and the area where the wind is blowing. Big waves, called swells, happen where there are large expanses of open water for wind to affect.

Question 4 of 15

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beach coastline
Photo: pavel ahmed/flickr
Where is the world's longest natural beach?

At roughly 75 miles long, Cox's Bazar beach in Bangladesh is the world's longest uninterrupted beach. Located along the Bay of Bengal, which is part of the Indian Ocean, the beach is one of Bangladesh's most popular tourist destinations.

Question 5 of 15

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sand bucket with shovel
Photo: downing.amanda/flickr
What color is the sand at Papakolea beach in Hawaii?

green sand on Papakolea beach in Hawaii
Located on the big island of Hawaii, the sands of Papakolea beach are green, thanks to large amounts of a mineral called olivine. The beach is at the base of a cinder cone formed by olivine-rich magma. As the cone erodes, olivine washes up on shore. (Photo: Sparkle Motion/flickr)

Question 6 of 15

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lifeguard stand at high tide on the beach
Photo: Erin Nekervis/flickr
How many high tides are there typically in one day?

With a few exceptions, most coastal areas experience two high tides and two low tides every lunar day (24 hours, 50 minutes), according to the National Oceanic and Atmospheric Administration (NOAA). High tide is when the water rises to its highest level on the shore, taking out beach chairs, umbrellas and everything in its wake.

Question 7 of 15

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Photo: Rennett Stowe/flickr
About how many miles of shoreline are there in the U.S. and its territories?

There are about 95,471 miles of shoreline in the United States and its territories, according to measurements done by NOAA in 1939-40. Shorelines of outer coasts, offshore islands, sounds, bays, rivers and creeks were included to the head of the tidewater or to a point where tidal waters narrow to a width of 100 feet.

Question 8 of 15

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feet in the sand
Photo: Leon Brocard/flickr
Where does beach sand come from?

The sand between your toes could have come from many different places. It could've blown there from barrier island dunes, washed there from rivers, formed by crushed shells or pushed ashore from far below in the continental shelf.

Question 9 of 15

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red tide
Photo: Mike/flickr
What is red tide?

Officially called harmful algal bloom, red tide occurs when simple plants that normally live in the water grow out of control, having harmful effects on fish, birds, other sea life and people. The toxins produced can kill fish, make shellfish dangerous to eat, turn the water red, and make the air hard to breathe.

Question 10 of 15

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boulders beach in south africa
Photos: Jochem Kooleflickr
What cool thing can you find at Boulders Beach in South Africa?

penguins on Boulder Beach in South Africa
A colony of about 3,000 endangered African penguins lives on Boulders Beach, growing from just two pairs that arrived in 1982. Part of Table Mountain National Park, the beach is a popular tourist destination because visitors can get so close to the penguins. (Photo: Graeme Churchard/flickr)

Question 11 of 15

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ocean waves breaking in shallow water
Photo: Dominic Alves/flickr
Why do waves break in shallow water?

According to NOAA, when the water's depth is half of a wave's wavelength, the wave starts to "feel the bottom." That means the deepest water molecules moved by the wave hit the seafloor. That forces the wave upwards and as the crest begins to lean forward, it topples over and breaks on the shore.

Question 12 of 15

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open hands holding black sand
Photo: Rob Lee/flickr
It's illegal to remove sand from Hawaii's black beaches.

Black sand beaches are formed by lava flow in a singular event so, unlike typical beaches, the sand is not replaced when it is washed away. In addition to being illegal, removing black sand or other native rocks is said to bring bad luck to the bold tourists who dare defy law and superstition.

Question 13 of 15

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nude beach
Photo: Phillip Pessar/flickr
How many states in the U.S. have clothing-optional beaches?

More than 20 states, including New Jersey, Texas and Nevada, have waterfront areas where you can sun in the buff. The American Association of Nude Recreation counts more than 250 clothing optional resorts, beaches and RV campgrounds in North America. (Tip: Wear a lot of sunscreen.)

Question 14 of 15

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dog in a sandbox
Photos: sgilsdorf/flickr
Which city creates a false beach every summer?

Paris-Plages, manmade beach along the Seine
Every July and August, sand is trucked into Paris as roadways along the Seine are blocked to make room for manmade beaches. The idea behind Paris-Plages was to give relief to Parisians who stay in town instead of going to the seaside during the height of tourist season. (Photo: ErasmusOfParis/flickr)

Question 15 of 15

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oldest beach in the U.S.
Photo: Boston Public Library/flickr
What is the oldest public U.S. beach?

The oldest public beach in the country, Revere Beach was established in 1896. Facing Massachusetts Bay, Revere Beach is about five miles north of Boston.