Topic
Ocean questions for kids
Here are 237 questions about the ocean from 19 A Million Whys books, each with a short video answer. Book 6, The Ocean Expedition is all about the ocean, and the rest come from other books in the series. Tap any question to watch the video and read the answer.
From Book 6: The Ocean Expedition (150)
Why Is the Ocean Salty?
Rain slowly wears tiny bits of salt and other minerals out of rocks. Rivers carry those bits to the sea.
Why Are There Waves?
Wind pushes on the surface of the water. That push travels across the sea as a wave.
Why Do Tides Go in and Out?
The Moon tugs on Earth's oceans, and the water bulges toward it. Earth turns under those bulges.
Why Is the Ocean Blue?
Sunlight looks white, but it is a mix of colors. Water soaks up reds and yellows first.
Why Does the Shore Keep Changing?
Waves, tides, storms, and rivers all move sand. A beach is a pile in motion.
Why Does Foam Show Up on Waves?
When a wave breaks, it mixes air into the water. Tiny bubbles form, and bits from living things in the sea help them stick together.
Why Can the Water Pull You Out?
Waves push extra water onto the beach. That water has to go back out to sea.
Why Do Tide Pools Appear?
When the tide drops, some seawater stays trapped in rocky bowls. Those bowls become tiny leftover oceans.
Why Is Some Sand Wet Under the Dry Top?
Sand is a pile of tiny grains with tiny gaps between them. Water hides in those gaps.
Why Is Beach Sand Often Tiny?
Waves tumble rocks for years and years. Big pieces smash and rub against each other.
Why Do Seashells Wash Up?
A shell is a leftover house. After the animal dies or leaves, waves carry the empty house to shore.
Why Does Seaweed Pile on the Beach?
Storms and strong waves tear seaweed loose. Many seaweeds have floats, so they drift on the water.
Why Does the Ocean Smell Like That?
The sea smell is a mix. It has salt spray, rotting seaweed, and gases from tiny living things.
Why Do Some Beaches Have Pebbles?
Not every shore has the time or the waves to grind rock all the way to powder. Strong waves can carry fine sand away and leave the heavier stones behind.
Why Do Waves Get Bigger Near Shore?
In deep water, a wave is a long, low shape. Near shore, the bottom crowds it from below.
Why Is There a Line of Junk on the Sand?
High tide pushes floating things up the beach. When the water falls, they stay where the tide stopped.
Why Is Some Sand Black?
Black sand is often tiny bits of dark volcanic rock. Or it can be heavy dark minerals left after the lighter grains wash away.
Why Does Wet Sand Hold a Castle?
A little bit of water acts like glue between sand grains. Too dry, and the walls crumble.
Why Do Footprints Fill with Water?
Under wet beach sand, there is more water. When you step, your foot squeezes the grains together.
Why Does Salt Help You Float?
Salt water is denser than fresh water. That means the same cup of water is heavier.
Why Is the Ocean Colder than a Puddle?
A puddle is thin and sits in the sun. The ocean is deep, and most of its water never gets a long turn in the heat.
Why Do Rocks Get Holes By the Sea?
Waves throw sand and pebbles at rocks. Soft spots wear away first.
Why Does Spray Feel Colder than the Air?
Spray is tiny drops of cold sea water. When it lands on you, it steals heat from your skin.
Why Is the Horizon a Straight Line?
Earth is huge and curved. From the beach, you only see a tiny slice of that curve.
Why Do Birds Follow the Tide Line?
When the water falls, it uncovers snacks like worms, tiny clams, and leftover bits. Birds walk the wet stripe like a moving buffet.
Why Do Fish Have Gills?
Fish pull oxygen out of the water with thin gill tissues. We air-breathers use lungs instead.
Why Don't Fish Drown?
Drowning happens when lungs fill with water, and fish do not use lungs. They use gills, which are built to pull oxygen out of water.
Why Do Fish Have Scales?
Scales are thin plates that cover a fish's body. They protect the fish and help it slip through the water.
Why Do Some Fish Swim in Schools?
Many eyes spot danger faster. A swirling crowd makes it hard for a hunter to pick one fish.
Why Are Fish Slippery?
Fish make a thin coat of slime called mucus. It helps them glide through water.
Why Can Some Fish Glow?
Some deep-sea fish make light inside their bodies with a chemical reaction. Others host glowing bacteria that live on them.
Why Is a Flounder So Flat?
Flatfish lie on the seafloor, and one side becomes the bottom. Both eyes move to the top side.
Why Does a Seahorse Look Like a Horse?
A seahorse is a fish in disguise. Its long snout sips tiny food, and its curled tail holds on to seagrass.
Why Does an Octopus Have Three Hearts?
An octopus is a mollusk, not a fish, and it has three hearts. Two hearts serve the gills, and a third heart serves the rest of the body.
Why Can an Octopus Change Color?
An octopus can match rock, sand, or coral in a blink. Tiny color cells in its skin open and close.
Why Do Crabs Walk Sideways?
A crab's legs fold out from the sides of its body. Its joints swing left and right more easily than front and back.
Why Does a Hermit Crab Wear a Shell?
A hermit crab's back end is soft. It slides into an empty snail shell and carries the house along.
Why Does a Starfish Have Five Arms?
A sea star is not a fish. Most kinds have five arms around a center.
Why Can a Starfish Grow an Arm Back?
A starfish is really called a sea star, because it is not a fish. If a sea star loses an arm, special cells can rebuild it.
Why Do Jellyfish Sting?
A jellyfish has no claws and no teeth. Its tentacles are covered in tiny stinging cells.
Why Isn't a Jellyfish a Fish?
A fish has a backbone, gills, and usually scales. A jellyfish has none of those!
Why Do Some Clams Make Pearls?
Some oysters and other mollusks can make pearls. If a bit of grit or a tiny parasite slips inside, the animal coats it with the same shiny material that lines its shell.
Why Do Some Fish Have Whiskers?
Some fish, like catfish, have whisker-like feelers near the mouth. They are called barbels.
Why Do Flying Fish Jump?
A flying fish shoots out of the water and spreads its long, stiff fins like wings. It does not flap like a bird.
Why Does an Eel Look Like a Snake?
An eel is a long fish. A snake is a long reptile.
Why Does a Pufferfish Puff Up?
When a pufferfish feels danger, it gulps water very fast. Its stretchy belly swells like a balloon, and its spines stick straight out.
Why Do Some Fish Live in the Dark?
Sunlight fades as you go deeper in the ocean. In the deep sea, it is dark all day and all night.
Why Doesn't an Anemone Sting a Clownfish?
A sea anemone has tentacles with stinging cells that can sting most fish. But a clownfish wears a special coat of mucus, which is a kind of slime.
Why Do Shrimp Dart Backward?
A shrimp can flip its tail fan under its body and shoot backward in a blink. Its tail is like a paddle, and one hard flex throws the shrimp away from danger.
Why Do Barnacles Stick So Hard?
A barnacle is a crustacean, so it is a cousin of crabs. A baby barnacle swims until it finds a spot.
Why Do Whales Breathe Air?
A whale looks like a fish, but it is a mammal, like you. That means it has lungs, not gills, and it must come up to breathe air.
Why Do Whales Have a Blowhole?
A blowhole is a whale's nose, but it sits on top of the head. Long, long ago, whale ancestors had nostrils on their snouts.
Why Do Some Whales Sing?
Some whales, especially male humpbacks, make long, patterned sounds called songs. Songs may help whales find a mate, or keep in touch across the sea.
Why Do Whales Travel So Far?
Many whales make long trips each year, called migrations. They feed in cold, food-rich water, and then swim to warm water to have their babies.
Why Is a Blue Whale So Huge?
The blue whale is the largest animal that has ever lived. Ocean water holds up its body, so it does not have to carry all that weight like a land animal would.
Why Do Some Whales Have Baleen Instead of Teeth?
Some whales have no teeth. Instead, they have baleen, a row of tough, fringed plates hanging from the upper jaw.
Why Do Dolphins Click?
Dolphins make rapid clicks, then listen for the echoes that come back. The echoes help them paint a picture of fish, nets, and the seafloor, even in murky water.
Why Do Dolphins Ride a Boat's Wave?
A moving boat pushes up a bulge of water at the front, called the bow wave. A dolphin can surf that moving slope, and keep up with almost no extra work.
Why Do Sharks Have So Many Teeth?
A shark's teeth grow in rows. When a front tooth falls out, a new one from the row behind moves up to take its place.
Why Do Many Sharks Keep Swimming?
Sharks breathe with gills, and gills need fresh water flowing over them. Many open-water sharks swim with their mouths slightly open, so water streams in all the time.
Why Do Some Sharks Look Like Carpets?
Carpet sharks, such as wobbegongs, have blotchy, patterned skin and little tassels around the mouth. That makes them look just like the reef floor.
Why Is a Great White Pale Underneath?
A great white is dark gray on top and white underneath. That is a trick called countershading.
Why Don't Most Sharks Hunt People?
Sharks hunt fish, seals, and other ocean animals. A person has a strange, bony shape and is not what sharks normally eat.
Why Does a Hammerhead Have a Hammer?
A hammerhead's head is a long, flat bar, with an eye at each tip. Under the head are special sensors that can feel faint electricity from other animals.
Why Can a Shark Smell a Tiny Bit of Blood?
A shark's nose is a pair of pits on its snout. Water flows in, and tiny sensors inside pick up smells.
Why Is a Ray So Flat?
Rays are related to sharks, and their bodies are flattened. Their wide fins work like wings, and many rays lie on the sand or glide just above it.
Why Does a Manta Look Like It Is Flying?
A manta ray flaps its huge, pointed fins up and down, and it looks like a bird in flight. But a manta is swimming, not flying.
Why Is a Whale Shark Not a Whale?
A whale shark is the biggest fish in the sea. It is a shark, not a whale.
Why Do Orcas Hunt Together?
Orcas are the largest members of the dolphin family, and they live in family groups called pods. Working together, a pod can catch meals that one orca could not.
Why Do Seals Climb Onto Rocks?
Seals hunt in the water, but they are mammals, so they need to rest on land. They climb onto rocks or sand to rest, warm up, dry off, and have pups.
Why Do Sea Turtles Come Back to a Beach?
Sea turtles often return to nest on the same stretch of coast where they hatched, even decades later. A mix of smell, Earth's magnetic field, and wave clues helps guide them home.
Why Is a Giant Squid So Hard to See?
Giant squid live far down in the ocean, where sunlight fades away. People almost never meet one alive.
Why Do Whales Have Blubber?
Blubber is a thick layer of fat under a whale's skin. It does three jobs: it keeps heat in, it stores energy, and it helps the whale float.
Why Do Whales Leap Out of the Water?
When a whale launches most of its body out of the water, that is called a breach. Scientists think a breach can send a message, knock off hitchhikers, or give the whale a look around.
Why Is a Manatee Called a Sea Cow?
A manatee is a gentle, slow mammal that grazes on seagrass and other water plants. People nicknamed it the sea cow, because its slow grazing looks like a cow in a field.
Why Is Coral an Animal, Not a Rock?
Coral looks like rock, but each tiny piece is an animal called a polyp, with a mouth and tentacles. The hard part is a limestone skeleton that the polyp builds around itself.
Why Do Corals Need Sunlight?
Many reef corals have tiny plant-like partners living inside them. They are called algae.
Why Do Reefs Look Like Cities?
A coral reef is like a bustling underwater city. Branches, caves, and ledges make apartments, shops, and hideouts for thousands of animals.
Why Do Corals Bleach?
When the water stays too warm for too long, corals get stressed. They push out the tiny algae that live inside them.
Why Can't You Stand on Coral?
Coral looks like a rock, but it is alive! It is a thin layer of living animals called polyps growing on a skeleton they built.
Why Is a Kelp Forest So Tall?
Giant kelp is a seaweed that races toward the light! It is a kind of algae, not a tree with wood.
Why Does Kelp Have Floats?
Kelp grows little gas-filled floats right next to its leaves, which are called blades. The floats work like life jackets, lifting the blades up toward the sunlight.
Why Do Otters Help Kelp?
Sea urchins love to munch on kelp. Sea otters love to munch on sea urchins!
Why Is Plankton So Important?
Plankton are tiny living things that drift in the water. Plant-like plankton make food from sunlight, and animal-like plankton eat them.
Why Does the Sea Sometimes Glow at Night?
Some tiny plankton and other sea creatures can make their own light! It happens through chemistry inside their bodies, and it is called bioluminescence.
Why Do Some Algae Make the Water Green?
Some tiny plant-like drifters, called algae, can fill the water with green. When there are lots of nutrients and strong sunlight, they multiply fast.
Why Do Sponges Have Holes?
A sea sponge is a living animal, not a kitchen sponge! It has no mouth.
Why Do Anemones Look Like Flowers?
An anemone looks like a flower, but it is really an animal! It is a close cousin of coral and jellyfish.
Why Do Parrotfish Poop Sand?
Parrotfish scrape algae off rocks and coral with a strong beak. They swallow bits of limestone along with it, and grinding teeth in their throats crush it into powder.
Why Do Cleaner Fish Pick at Bigger Fish?
Cleaner fish and cleaner shrimp eat pests and dead skin off bigger fish. The big fish gets cleaned, and the cleaner gets a meal.
Why Do Mangroves Grow in Salt Water?
Mangroves are special trees that grow in salty mud along tropical shores. Some of their roots poke up like snorkels to get air.
Why Are Seagrass Beds Called Nurseries?
Seagrass is a real flowering plant that grows in shallow sea water. Its blades make a leafy maze where young fish, crabs, and turtles find food and cover.
Why Do Some Reefs Grow in Rings?
A ring reef is called an atoll. It starts as coral growing around a volcanic island.
Why Is a Lagoon Calmer than the Open Sea?
A lagoon sits behind a reef or an island. The reef works like a breakwater, a wall that takes the punch of big ocean waves.
Why Do Some Snails Have Bright Colors on a Reef?
Reef snails like cone snails and cowries can have bold, bright patterns. Sometimes the colors help the snail hide, which is called camouflage.
Why Do Christmas-Tree Worms Vanish?
Those little colorful trees on a Christmas-tree worm are really its gills and feeding fans. The worm lives safely in a tube in the coral.
Why Do Some Corals Come Out at Night?
Many corals tuck in during the day and reach out at night. Night water can be rich in drifting plankton.
Why Is the Water Around a Reef So Clear?
Reef corals need sunlight for their algae partners. Sunlight can only reach them if the water has few floating specks.
Why Do Scientists Plant Coral?
Scientists grow tiny pieces of coral in nurseries. Then trained teams attach them to damaged reefs, where they can grow into new colonies.
Why Does a Tiny Change in Heat Hurt a Whole Reef?
Reef corals live in warm water, but near their heat limit. A little extra warmth for too long can cause bleaching.
Why Do Ships Float?
A ship is a steel bowl full of air! The water pushes up on the ship, and that push is called buoyancy.
Why Is a Keel on the Bottom of a Boat?
A keel is a fin or a heavy spine under a boat. It keeps a sailboat from sliding sideways in the wind.
Why Do Big Ships Have Such Small-Looking Propellers?
A big ship's propeller looks small next to its huge hull. But up close, its blades can be taller than a person!
Why Does a Lighthouse Flash?
A lighthouse is a tall lamp with a fingerprint. Each one flashes its own pattern, like long, short, pause.
Why Did Sailors Use Stars to Find Their Way?
Before GPS, sailors found their way by measuring the angle of a star above the horizon. Add the exact time, and that helps tell where you are.
Why Is a Compass Needle Twitchy on a Ship?
A magnetic compass needle points toward Earth's magnetic north. But a steel ship has its own magnetic pulls, from the steel hull, engines, and electric wires.
Why Are There Lines on a Nautical Chart?
A nautical chart is a map for the water. Its lines and numbers show depths, shallow spots, rocks, wrecks, and safe channels.
Why Do We Use Latitude and Longitude?
Latitude and longitude are two numbers that name any spot on Earth. Latitude tells how far north or south of the equator you are.
Why Is the International Date Line in the Pacific?
Earth needs a line where the calendar date jumps. That is the International Date Line, and most of it runs through the middle of the Pacific Ocean.
Why Does a Submarine Go Up and Down?
A submarine has special tanks called ballast tanks. Filling them with seawater makes the sub heavier than the water it pushes aside, so it sinks.
Why Do Submarines Make So Little Wake on the Surface?
A wake is the trail of waves left by a hull cutting the surface. A submarine that runs deep stays below that surface.
Why Do Scientists Use Sonar?
Sonar sends out a ping of sound, and then listens for the echo. The time the echo takes to come back tells how far away something is.
Why Is the Seafloor Mapped in Strips?
The ocean is huge, so one ship can only see a skinny strip at a time. A mapping ship uses sonar that sees a wide band, called a swath, under the hull.
Why Do Research Ships Drag Nets and Bottles?
You can't understand the sea just by looking from the deck of a ship. So scientists bring a little bit of the ocean aboard!
Why Is a Weather Buoy Left Alone in the Ocean?
A weather buoy is a floating robot weather station. It sits in the ocean for months, measuring wind, waves, temperature, and air pressure.
Why Do Satellites Watch the Sea From Space?
From space, one picture can show a storm, a bloom of tiny plants, and a current all at once! Satellites measure sea color, sea height, temperature, and ice.
Why Is There a Dead Zone in Some Coastal Water?
A dead zone is a patch of water with too little oxygen for most animals to live in. Extra nutrients from farms and cities can cause a feast of algae.
Why Do Currents Move Like Rivers in the Sea?
An ocean current is like a river with no banks. It's a huge stream of water that flows through the sea.
Why Is the Gulf Stream Famous?
The Gulf Stream is a strong, warm ocean current. It leaves the Gulf of Mexico, runs up the east coast of the United States, and then heads across the Atlantic toward Europe.
Why Do Containers Stack So High on a Ship?
Shipping containers are strong steel boxes with special corners. Those corners lock together, so boxes can be stacked into a tall, tidy warehouse right on the deck.
Why Do Harbors Need Pilots?
A harbor pilot is a local expert who steps aboard a big ship to guide it through a busy port. The captain knows the ship.
Why Do Some Boats Have Two Hulls?
A catamaran has two slim hulls joined by a deck. That wide stance makes the boat harder to tip over.
Why Does a Life Jacket Work?
A life jacket is filled with foam or air that is much lighter than water. That gives you extra buoyancy, an upward push, so your mouth and nose can stay above the water even if you get tired.
Why Do Divers Need Tanks?
People can't breathe underwater, because our lungs can't pull oxygen out of water the way gills do. So divers carry tanks that hold compressed air, which is air squeezed into a small space.
Why Is the Deep Ocean So Hard to Visit?
The deep ocean is dark, cold, and under enormous pressure. Down there, the water above is so heavy that it could crush an ordinary submarine.
Why Do Hurricanes Grow Over Warm Ocean Water?
A hurricane is like a giant heat engine, and warm ocean water is its fuel. Warm seawater evaporates and rises as moist air.
Why Does a Storm Surge Flood a Coast?
A storm surge is seawater pushed onto land by a storm's strong winds and low air pressure. It isn't just rain!
Why Do Sea Walls Sometimes Make Beaches Worse?
A sea wall is a hard barrier that protects buildings from waves. But a wall bounces wave energy back instead of absorbing it.
Why Do Wetlands Protect Towns From Storms?
Wetlands, like salt marshes and mangroves, act like a sponge and a speed bump for storm water. They are places where land and sea mix.
Why Is Plastic in the Ocean a Problem?
Plastic is built not to rot, so it lasts a very long time in the sea. Waves and sunlight break it into smaller and smaller bits, but those bits don't turn into food.
Why Do Helpers Cut Six-Pack Rings?
Plastic six-pack rings are loops that can trap animals. A loop can slip over a bird's neck or a turtle's flipper, and it can tighten as the animal grows.
Why Do Sea Turtles Eat Bags?
Sea turtles eat jellyfish. A pale plastic bag floating in the water can look a lot like one.
Why Is Oil in Water So Hard to Clean?
Oil and water don't mix. Spilled oil floats, spreads into a thin film, and gets pushed around by wind.
Why Do Beaches Need a Cleanup Day?
The tide drops new trash on the beach, again and again. It is like a delivery service nobody ordered.
Why Do Some Sunscreens Hurt Reefs?
Some chemical filters in sunscreen wash off swimmers and into the water. A coral reef is a living neighborhood of tiny animals.
Why Do We Measure the Ocean's Temperature?
The ocean is like Earth's giant thermometer. Ships, buoys, satellites, and diving robots all take its temperature.
Why Is Sea Level Rising?
Sea level is rising for two main reasons. First, warm water takes up a little more room, which is called thermal expansion.
Why Do Ice Sheets Matter to a Beach Far Away?
Greenland and Antarctica hold huge ice sheets on land. When that ice melts or slides into the sea, it adds water to the whole ocean, because the ocean is one connected bowl.
Why Does Extra Carbon Dioxide Change Seawater?
The ocean drinks in some of the extra carbon dioxide that we put in the air by burning fuel. Carbon dioxide and water make a weak acid, so the sea becomes a little less basic.
Why Do Scientists Tag Fish and Turtles?
You can't follow a turtle across the ocean on a bike! So scientists use small tags and satellite packs, so animals can report where they feed, nest, and hide.
Why Is a Marine Park a Kind of Fence?
A marine park, or marine reserve, marks off a part of the sea where fishing, anchoring, or collecting is limited or stopped. The fence isn't made of boards.
Why Do Fishers Use Limits and Seasons?
A limit caps how many fish a boat may keep. A season closes the water during spawning, when fish are making babies.
Why Should You Put a Shell Back If a Creature Is Inside?
A pretty shell on the beach might have a snail, a hermit crab, or a clam inside. Taking it home means taking a living animal away from its home in the sea.
Why Is Dumping Aquarium Fish in the Sea a Bad Idea?
Aquarium fish, plants, and snails can survive and breed in places they don't belong. If they escape into the wild, they can crowd out the native animals.
Why Do Ships Have Rules About Ballast Water?
Ships take in ballast water to stay balanced, and let it out later. That water can carry tiny animals, plants, and larvae across the ocean.
Why Do Some Coasts Restore Dunes?
A dune is a sand hill held together by roots. It's a living wall that can grow back after a storm!
Why Should a Tide-Pool Visit Be Look, Don't Poke?
A tide pool is like a tiny bathtub neighborhood for anemones, crabs, and small fish. Poking or turning rocks can crush animals or dry them out.
Why Does Turning Off Extra Lights Help Hatchling Turtles?
Baby sea turtles hatch at night and crawl toward the brightest, lowest horizon, which is usually the sea. But street lights and porch lights can confuse them and pull them inland instead.
Why Do Kids' Small Habits Still Matter for the Ocean?
Most ocean trash and chemicals start on land, on streets, in yards, and at picnic tables. Rain and wind carry leftovers into drains and rivers, and rivers flow to the sea.
Why Is the Ocean Worth a Whole Expedition?
The ocean makes rain, makes much of our oxygen, carries heat, and hides mountains and coral cities. It touches our weather, our food, and our stories.
From Book 1: The Great Expedition (6)
Why Do Sharks Have So Many Teeth? A Conveyor Belt of Chompers!
Sharks are tooth experts! Their teeth are tools that fall out when worn or loose, and behind the front teeth are backup rows waiting their turn, like a conveyor belt.
Why Do Whales Sing? Songs That Travel for Miles!
Whale songs are some of the ocean's most amazing sounds! Sound travels far in water, and the page says whale songs can travel for miles.
Why Do Octopuses Seem So Smart? Eight Clever Arms!
Octopuses have big brains for invertebrates, which helps them learn, remember and solve problems. Their arms are packed with neurons, so the arms can act on their own,...
Why Do Tides Rise and Fall? The Moon's Big Pull!
Twice a day, the ocean creeps up the beach and then slides back out. The Moon's gravity pulls on Earth's oceans and makes water bulge, with one bulge on the side facing the Moon and another on the opposite side.
Why Do Rivers Flow to the Sea? Water Always Runs Downhill!
Rivers start small! Raindrops on a hillside trickle into tiny rills, rills join to become streams, and streams merge into rivers, all because water runs downhill.
Why Do Hurricanes Spin? Ocean Heat and Earth's Twist!
Hurricanes are powered by warm ocean water. Heat makes moist air rise, which creates low pressure, and cooler air rushes in to take its place.
From Book 2: The Inside Expedition (1)
From Book 3: The Built Expedition (2)
From Book 4: The Wild Expedition (1)
From Book 5: The Time Expedition (2)
Sea Monsters? Why Were There Giant Sea Reptiles Too?
While dinosaurs walked on land, big reptiles like ichthyosaurs and plesiosaurs swam in the oceans. They were not dinosaurs, but they lived at the same time.
Seashells Far From the Sea! Why Did People Trade Them?
Shells found far from the ocean show that objects moved long distances. People may have traded or passed them along as jewelry or special items.
From Book 7: The Weather Expedition (4)
Why Do Hurricanes Need Warm Ocean Water?
A hurricane is like an engine, and warm ocean water is its fuel. The sea has to be about 26 degrees Celsius, or 80 degrees Fahrenheit, or warmer, and that warm water has to go down deep.
Why Do We Feel Wind More on Hills and Beaches?
Wind feels stronger on hills and beaches because there is less in its way. Cities and forests slow the wind down with buildings and trees.
Why Do Oceans Store So Much Heat?
Oceans store so much heat because water can hold a huge amount of heat energy. They soak up energy from the Sun and release it slowly, which shapes climates around the world.
Why Do Pilots and Sailors Need Forecasts?
Airplanes and ships travel for hours across big open spaces, and weather changes along the way. Pilots and sailors need to know about wind, waves, clouds, and storms before they leave.
From Book 8: The Space Expedition (4)
Why Are There Two High Tides a Day, Not One?
Most coasts get two high tides a day because the Moon stretches the ocean into two bulges! The Moon pulls hardest on the nearest ocean, less on Earth, and least on the far ocean.
Why Are Some Tides Especially High (Spring Tides)?
Spring tides are especially high because the Sun and Moon line up! At new or full Moon, their pulls add together, so the oceans bulge more.
Why Might Icy Moons Hide Oceans?
Icy moons might hide oceans because a giant planet's pull can flex them and make heat inside! That inner warmth can melt some of the ice deep down.
Why Clean Spacecraft Before Visiting Ocean Worlds?
We clean spacecraft before visiting ocean worlds so we don't bring Earth germs to alien seas! If Earth microbes hitched a ride, they could confuse our science and might even harm unknown life.
From Book 11: The Animal Expedition (10)
Why Does Shark Skin Feel Like Sandpaper?
Shark skin feels like sandpaper because it is covered in tiny tooth-shaped scales! These little scales are called denticles.
Why Do Sharks Sense Tiny Electric Twitches?
Sharks sense tiny electric signals with special pores near their snouts! All animals give off very weak electricity when their muscles move.
Why Do Octopuses Taste with Their Arms?
Octopuses taste with their arms because their suckers have taste sensors! Each sucker has taste and touch sensors.
Why Do Dolphins Babysit Each Other’s Calves?
Dolphins babysit each other's calves because it takes a team to raise little ones! In some groups, adults watch the calves while the mothers go hunting.
Why Do Octopuses Squirt Ink?
Octopuses squirt ink because it helps them escape when they are scared! The dark cloud is a decoy, and it gives the octopus time to get away.
Why Do Remora Fish Stick to Sharks?
Remora fish stick to sharks because they get a free ride and a free meal! A remora has a flat sucker on top of its head.
Why Do Sea Otters Use Rocks as Tools?
Sea otters use rocks as tools because it helps them open hard-shelled food! They eat shellfish like clams and crabs.
Why Do Ghost Crabs Dig Burrows on the Beach?
Ghost crabs dig burrows on the beach to stay cool, damp, and hidden! The hot sun can dry a crab out.
Why Do Coral Reef Fish Stay Near Home Ranges?
Coral reef fish stay near home because knowing a place well helps them survive! They learn where food is and where to hide.
Why Do Sperm Whales Dive So Deep?
Sperm whales dive so deep because their favorite food lives in the dark depths! They can dive over a thousand meters.
From Book 12: The Volcano Expedition (2)
Why Do Matching Rock Belts Appear Across Oceans?
Rocks on opposite sides of the Atlantic Ocean match each other! Rocks in Newfoundland and in Scotland are the same age and type.
Why Are Some Beaches Green?
Some beaches are green because their sand is made of tiny green crystals from volcanic rock. The crystals are a mineral called olivine.
From Book 14: The Sound Expedition (3)
Why Can You Hear the Ocean in a Seashell?
The ocean sound in a seashell is not really the ocean! It is the quiet noise all around you, made louder by the shell's hollow space.
Why Do Some Beaches Have Singing Sand?
Singing sand makes sounds because layers of sand grains slide over each other together! That slipping makes a steady vibration.
Why Did Sailors Blow a Horn Near Cliffs and Listen for the Echo?
Sailors blew a horn near cliffs to use the echo as a safety check in fog! When they could not see the shore, the echo told them how close it was.
From Book 16: The Desert Expedition (4)
Why Do Fossils of Sea Creatures Turn Up in Some Deserts?
Parts of some deserts used to lie under warm, shallow seas millions of years ago! Shells and sea animals sank into the mud, and the mud hardened into rock.
How Can Desert Dust Blow Across a Whole Ocean?
Winds can carry fine desert dust high into the air, where it rides along for thousands of miles! Dust from the Sahara blows across the Atlantic Ocean in about a week.
Why Are Some Desert Lakes Saltier than the Ocean?
Some desert lakes are saltier than the ocean because water can only leave them by evaporating! When the water evaporates, the salt stays behind.
How Can Old Lake Shorelines Show Up on Desert Mountainsides?
Old lake shorelines show up on desert mountainsides because huge lakes once covered the land and then shrank! Waves carved level ledges into the mountains, like rings in a bathtub.
From Book 18: The Polar Expedition (26)
What Is the Arctic Ocean Like?
The Arctic Ocean is the smallest and shallowest ocean on Earth, and it is covered with sea ice in winter! It sits at the top of the world, surrounded by land.
What Is the Southern Ocean?
The Southern Ocean is the ring of cold water that circles Antarctica, and many scientists call it the fifth ocean! It has strong winds and giant waves.
What Is the Difference Between Sea Ice and an Ice Sheet?
Sea ice is frozen seawater that floats, and an ice sheet is a giant thick layer of ice sitting on land! They are both ice, but they are very different.
How Does Ocean Water Turn Into a Sheet of Ice?
Ocean water turns into ice when it gets cold enough, but salty water needs to be colder than freshwater to freeze! Tiny crystals start the process.
Why Is Old Sea Ice Less Salty than the Ocean It Came From?
Old sea ice is less salty than the ocean it came from because the salt slowly drains out of it! Over time, the ice becomes much fresher.
Why Do Pancakes of Ice Form on the Ocean?
Pancakes of ice form when waves bump and rub slushy ice into round plates! They look just like pancakes floating on the sea.
Why Does the South Pole Get Less Sunshine Over a Year than a Sunny Beach?
The South Pole gets less sunshine over a year than a sunny beach because the Sun is always low there, and it is gone for half the year! Its light is weak and spread out.
Why Are Polar Seas So Full of Life?
Polar seas are full of life because cold water is packed with oxygen and nutrients! In summer, the Sun shines almost all day long.
What Lives on the Underside of Sea Ice?
Under sea ice lives a hidden garden of tiny plants called ice algae! They grow in brown and golden streaks on the bottom of the ice.
Why Is Sea Ice a Nursery for Baby Animals?
Sea ice is a nursery because it gives young animals safety, warmth, and food! Many babies are born or grow up on and around the ice.
Who Eats Whom in the Antarctic Ocean?
In the Antarctic ocean, almost everyone eats or is eaten, starting with tiny plants! Krill sit in the middle of the whole web.
Why Do Whales Visit Polar Seas to Eat?
Whales visit polar seas to eat because summer there is an enormous buffet! The water is full of krill and fish.
How Can a Bowhead Whale Live for 200 Years?
Bowhead whales can live around 200 years, longer than any other mammal! They live in cold water and grow very slowly.
Why Does the Southern Ocean Circle All the Way Around Antarctica?
The Southern Ocean circles Antarctica because no land blocks the water! Strong winds push it around the continent from west to east.
Why Does Sinking Cold, Salty Water Matter for the Ocean?
Sinking cold, salty water matters because it carries oxygen and heat all around the ocean! Very cold, salty water is heavy, so it sinks.
Why Are Some Antarctic Sea Creatures So Big?
Some Antarctic sea creatures grow extra big, and scientists call this polar gigantism! Sea spiders can be as big as a dinner plate.
How Old Can a Greenland Shark Get?
A Greenland shark may live for hundreds of years! Scientists estimate some are 250 to 500 years old.
Do Corals Live in Cold Polar Waters?
Yes, corals live in cold polar waters, too! These cold-water corals live deep in the dark sea, where there is no sunlight.
Why Is the Edge of the Sea Ice a Feeding Hotspot?
The edge of the sea ice is a feeding hotspot because the meltwater there sets off a feast! Fresh meltwater floats on top of the salty sea.
Why Are Polar Seas Busy in Summer and Quiet in Winter?
Polar seas are busy in summer and quiet in winter because the Sun brings the food! In summer, nearly nonstop sunshine makes plankton bloom.
How Do Scientists Explore Under Polar Sea Ice?
Scientists explore under polar sea ice using cameras, robots, and special vehicles! These tools let researchers look beneath thick ice.
How Do Ships Find a Path Through Sea Ice?
Ships find a path through sea ice by reading clues from the water, the air, and even space! Ice pilots look for open channels, and satellites show where the ice is thick or thin.
Why Does Melting Land Ice Raise Sea Level but Melting Sea Ice Does Not?
Melting land ice raises sea level, but melting sea ice hardly does! Sea ice already floats in the water, and it takes up as much space as it weighs.
What Happens to Seals and Seabirds When Sea Ice Shrinks?
Seals, seabirds, and other animals use sea ice, so changes in the ice mean changes for them. When the ice forms later or melts earlier, animals may need to adapt.
How Do Seals Help Scientists Study the Ocean?
Seals help scientists by carrying tiny sensors into places no ship can go! The sensors measure the ocean while the seal swims and dives.
Can You Make Sea Ice at Home?
Yes, you can make sea ice at home, with a grown-up's help! Stir salt into water and chill it in the freezer.
From Book 19: The River Expedition (8)
Why Are River Valleys Shaped Like a V in the Mountains but Wide Near the Sea?
High in the hills, a river valley looks like the letter V! Near the sea it is wide and flat.
What Happens Where a River Meets the Sea?
The place where a river meets the sea is called an estuary! Fresh river water mixes with salty seawater.
Where Does River Water Go After It Reaches the Sea?
River water goes back up into the sky after it reaches the sea! The Sun heats the ocean, and the water travels in a big circle called the water cycle.
How Can You Follow a Raindrop From Your Street to the Sea?
A raindrop that lands on your street takes a trip to the sea! It flows to the gutter, into a storm drain, and through pipes to a nearby creek or river.
How Do American Eels Swim From Rivers to the Faraway Sargasso Sea?
American eels grow up in rivers, then swim all the way to the Sargasso Sea to have babies! The Sargasso Sea is a part of the Atlantic Ocean near Bermuda.
Can Dolphins Live in Fresh Water?
Yes! A few kinds of river dolphins live in big rivers in Asia and South America!
How Can Ocean-Going Ships Sail Deep Inside a Continent?
Ocean-going ships can sail deep inside a continent using a system called the St. Lawrence Seaway!
Can the Ocean Push a River Backward?
Yes, the ocean can push a river backward, near the coast! When the tide comes in, the sea pushes up into the river mouth.
From Book 20: The Mountain Expedition (1)
From Book 21: The Magnet Expedition (6)
Why Can a Magnet Pull Black Grains Out of Beach Sand?
Walk along some beaches and you might spot dark streaks in the sand. Those streaks hide tiny black grains that a magnet can pull right out.
Why Is There a Weak Spot Over the South Atlantic Ocean?
Earth's magnetic field is strong in some places and weak in others. Over South America and the South Atlantic Ocean, it is weaker than almost anywhere else.
How Did Sailors Steer Before GPS?
Long ago, sailors crossed whole oceans without GPS. They did it by combining many simple tools, and a lot of careful thinking.
How Did Pacific Wayfinders Cross Oceans Without a Compass?
Thousands of years ago, brave sailors crossed huge oceans in canoes. They had no compasses, and no maps, and yet they found tiny islands in the Pacific.
How Do Sea Turtles Use Earth’s Magnet to Find Their Way?
A baby sea turtle hatches on a beach, swims out to sea, and years later returns to lay its eggs on the very same beach. How does it find its way across a huge ocean?
Can Sharks Use a Magnetic Map to Swim Home?
Sharks swim across huge oceans and somehow find their way home. Scientists wondered if they might use a magnetic map.
From Book 22: The Energy Expedition (3)
How Do Deep-Sea Animals Get by with So Little Food?
The deep ocean is dark and cold. No sunlight reaches it, so no plants grow.
How Does a Tidal Power Station Use the Ocean?
The ocean rises and falls twice every day. That is the tide, and it has a lot of energy.
How Can Ocean Waves Make Electricity?
Ocean waves never stop moving. That motion is energy.
From Book 23: The Flight Expedition (2)
From Book 24: The Underground Expedition (2)
How do builders make tunnels under rivers and seas?
One method is to dig a trench in the river bottom and sink tunnel sections built on land. The sections float like boats and then are lowered and joined in the trench.
Why do some oil wells stand out in the ocean?
Some oil lies in rock far below the sea floor. To reach it, workers build an offshore platform that sits on legs or floats and is held in place by strong anchors.