pathfinder edition nationalgeographic.com/ngeXplorer January-february 2008

Lizardsliving With a Volcano 8 oil 16

2Lizards

LizardsLizards Great Escape ArtistsBy Rene Ebersole

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I am nose-to-nose with the strangest lizard I have ever seen. “This is a thorny devil,” my friend says. He is holding an animal with spikes running up and down its back. Up close, the thorny devil looks like a tiny dinosaur.

My friend puts the lizard back on the ground. It tries to look tough and scary. It puffs its chest out. Its sharp tail sticks straight up. It may look scary, but I know this pint-sized critter is actually terrified. I watch as the lizard slowly sneaks off. It keeps a close eye on us as it crawls away.

Trying to look scary is just one of the adaptations lizards have to outsmart, outlast, or outrun their predators. Watching the thorny devil made me think of other wacky and wonderful ways lizards stay safe. I’m sure you’ll agree that these critters are great escape artists.

Benefits of Being BlueSome lizards avoid trouble by being blue. Take the blue-tongued skink. You guessed it—this brown lizard has a royal blue tongue. At first, a snake may think it’s an easy meal. Yet when the snake tries to attack it, the little lizard has a big surprise ready.

Suddenly, the lizard sticks out its bright blue tongue, puffs up its body, and hisses loudly. The startled attacker takes off in search of a meal that’s easier to catch.

Being blue helps another lizard as well. The blue-tailed skink is brown with light stripes. However, its tail is bright blue. The blue color attracts predators to the tail and distracts them from the rest of the lizard’s body. That’s a good thing! This is a trick tail, you see.

When a hungry hawk grabs the tail, it falls off. Dropping a body part this way is called autotomy. The tail is left behind for the hawk to gobble up, and the lizard scampers to safety.

Nasty Surprise The horned lizard has its own way of escaping danger. This critter spends most of its time munching on ants and watching out for the birds of prey that want to gobble it up.

Although the lizard is covered with sharp spikes and horns, it’s actually harmless. Its brown, flat body helps it blend in with the desert habitat. Blending in this way is called camouflage. Lots of lizards use camouflage. Sometimes a predator can walk right past a lizard and not even know it’s there!

Camouflage doesn’t work every time, however. Luckily, the horned lizard has a backup plan. If an attacker sees it, the lizard waits until the attacker is about a meter (three feet) away. Then it squirts a stream of blood out of the corner of its eye.

The lizard’s aim is very good. As you might imagine, the blood tastes awful. The blood-covered predator usually runs away.

Serious Spikes. The thorny devil may look dangerous, but it’s not really harmful. The spikes are just a tool to keep predators away.

Tricky Tail. If a blue–tailed skink is attacked, it sheds its tail and runs to safety. A new tail grows in about a year.

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Get Lost! A blue–tongued skink scares predators away by sticking out its large, royal blue tongue.

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Fancy Feet and ToesNot all lizards can scare off their predators. Some of these critters depend on making a quick getaway instead.

Take the basilisk lizard, for example. It can run on water to make a quick escape. That’s a good thing because there are lots of predators in this lizard’s rain forest home. It has to watch out for hungry snakes, birds, and mammals.

How can the basilisk run on water? It’s all about the feet. This lizard has big feet that look a bit odd with its small body. The feet come in handy, though. Between the toes are flaps of skin that the lizard can spread out.

The flaps let the lizard dash short distances across the water. It can cover about 5 meters (15 feet) this way. Then the lizard drops down into the water and uses its super swimming skills to finish the getaway.

A gecko escapes in another way. It has tiny hairs on the bottom of its toes. Those hairs work like suction cups and stick to surfaces. That means a gecko can scurry up walls or scamper across ceilings to places where predators can’t follow.

Stay Where You AreSome kinds of lizards cannot scare predators away. They can’t outrun them either. Instead, they escape danger by staying put. That is what the armadillo lizard does.

At the first sign of danger, the lizard reaches down and grabs its tail with its mouth. It then curls up into a tight ball. It looks more like a hard, spiky rock than a tasty snack. Its sharp spines make predators think twice. A mouthful of spikes isn’t very tasty.

The chuckwalla lizard doesn’t look like a rock, but it does use rocks to stay safe. This lizard lives in many rocky, desert areas. It spends most of its day soaking up the hot sun, snacking on plants and flowers.

When danger is near, the lizard scurries inside the closest crevice, or a crack in a rock. It takes a deep breath and puffs its body up like a balloon. Its puffed-up body wedges tightly into the crevice.

The predator reaches and grabs. It yanks and pulls. Yet it can’t get the lizard out. The disappointed predator gives up. Meanwhile, the lizard can breathe easy again.

Long Live the LizardAs you can see, lizards have many ways of outlasting their predators. Thanks to wild and wonderful adaptations, lizards have survived for many millions of years.

Next time you find yourself exploring the great outdoors, look closely. Maybe you’ll spot one of these amazing escape artists.

Wordwiseautotomy: ability to voluntarily let go of a body part

camouflage: hiding by blending into the surroundings

crevice: crack in a rock

habitat: place where an animal lives

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Feet Flaps. This basilisk lizard uses flaps between its toes to run on water and dash away from danger.

Sticky Feet. Special hairs on a gecko’s toes help it grip onto surfaces, such as these leaves.

Tough Meal. An armadillo lizard grabs its tail in its mouth to form a tight ball. That makes it tough for predators to bite into.

Tough Meal. An armadillo lizard grabs its tail in its mouth to form a tight ball. That makes it tough for predators to bite into.

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Reading Strategy: As you read, use the author’s words to form pictures in your mind. What do you see, hear, smell, and feel?

Explore a forgotten city destroyed by an

ancient volcano.

Living With

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By Tom O’Neill

Most people escaped when Mount Vesuvius erupted in a.d. 79. This statue shows one of those who did not.

FLAT EARTH ROYALTY FREE PHOTOGRAPH (BORDER); © ROGER RESSMEYER/CORBIS (STATUE)

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Boom! About 2,000 years ago, a volcano called Vesuvius roared to life. Hot clouds of gas shot into the sky. Burning rocks whirled through the air. Hot ash poured from the volcano.

An unlucky town was located nearby. A thick layer of ash soon covered it. The town was called Pompeii.

The ash wasn’t the only problem the town faced. A flood of boiling mud rushed down the volcano. Poisonous gases filled the air. Everything for miles around was destroyed. Anyone who did not escape the city died.

Puzzle PiecesSo what caused all the mayhem? Well, the answer lies buried deep underground. That’s where all volcanoes have their roots. Vesuvius is no different.

Earth is not as solid as you may think. Its surface is made of many plates. Those are large pieces of Earth’s crust. They fit together like a jigsaw puzzle.

The plates don’t sit still. Each plate is moving in different directions. Sometimes plates even slam into one another. That’s what happened under Pompeii. For millions of years, two plates have been colliding there.

Hot SpotThe plates colliding under Pompeii carved an opening in Earth’s surface. Magma, or melted rock, rose up into the opening. Then it oozed out onto Earth’s surface.

Magma that reaches Earth’s surface is called lava. Layers of hot lava and ash built up around the opening. That’s how the volcano started to form. The layers of lava and ash slowly hardened and grew into the mighty volcano that would one day destroy Pompeii.

A volcano made from layers of lava and ash is called a composite volcano. It has steep

sides and a crater at its top. Vesuvius is a composite volcano.

Composite volcanoes are just one kind of volcano. Some volcanoes are made of mostly lava. Other volcanoes are made of mostly ash.

Some of these other volcanoes erupt gradually. Lava slowly flows out

of them. Not composite volcanoes. They explode. That is what Vesuvius did in a.d. 79. It was one of the most famous eruptions ever.

For two days, ash fell on Pompeii. It piled up like snow. In some places, the layer of ash was four meters (twelve feet) high. At the same time, a river of mud rushed down the side of the volcano. The ash and the mud completely buried Pompeii and nearby towns.

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Violent Volcano. Vesuvius erupted with a huge boom. Hot ash and rock shot high into the sky and covered the nearby area.

On the Run. Many people lived near the volcano. They tried to escape the eruption. Most made it to safety, but some did not.

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Digging Into the PastOver time, people forgot about Pompeii. The top layer of ash covering the town turned into rich soil. People built farms and villages where the town used to be. No one realized what was buried under their feet.

That changed about 500 years ago. That is when some workers digging in the area discovered the unknown city. They found pieces of marble, a kind of stone. They discovered painted walls. They dug up statues. Slowly, the forgotten town once again rose from the ground.

Treasure hunters were the first people to explore the age-old city. Instead of trying to learn about it, they stole its treasures. They took gold, coins, jewelry, and statues. We may never know all the treasures they took or destroyed.

Finally, archaeologists took over. They are scientists who study places and things from the past. They knew how to excavate, or dig in a careful, scientific way. They went right to work.

They cleared the rubble. They chipped away the rest of the ash and mud covering the ancient town. They wrote notes and drew maps. Doing all these things helped them learn how people in Pompeii lived.

The Past in the PresentThe ash that blanketed Pompeii preserved the town almost perfectly. Much of the city looks just as it did 2,000 years ago. Houses look as if their owners might come back at any minute. Inside one house, there is a picture of a dog. Below it are the words “Beware of Dog.” Snack bars look ready for hungry customers to sit down for a meal. Eighty-one loaves of bread were found in an oven in one bakery. They looked almost ready to eat! Unfortunately, they have all turned to stone.

Two large theaters lie in the middle of the city. The benches that the people sat on to watch plays are still there. So are roads, paved with stone and ready for horse-drawn carts.

Beware of Dog. This tile decoration of a dog once lay just inside the door of someone’s house. It warned thieves to stay away.

Glass From the Past. The volcanic ash formed a protective layer that kept these glass vases and other items in good shape.

Not–So–Fresh Bread. Archaeologists found 81 loaves of bread still sitting in an oven. Over time, the bread had turned to stone.

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Pompeii Preserved. Volcanic ash blanketed Pompeii. Under the ash, the town stayed basically the same as it was.

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Frozen in TimePerhaps you are wondering what happened to the people of Pompeii. Many escaped. Yet some people remain in the city as plaster statues.

Some 20,000 people lived in Pompeii. Most of them ran into the countryside when the volcano erupted. They escaped the disaster.

About 2,000 people did not. Hot ash covered them. Over time, the ash turned to rock. The people’s bodies decayed and disappeared.

After a body decayed, it left a hollow place in the rock. The hollow place was shaped just like the person’s body. Archaeologists filled the hollow places with plaster. The plaster hardened to form statues. This kind of statue is called a plaster cast.

The statues are very detailed. You can see the people’s faces very clearly. Some people’s arms are up, trying to shield their faces. The statues are a constant reminder of what happened at Pompeii long ago.

Looking to the FutureToday, about three million people live near Vesuvius. They have built homes and businesses. Life goes on as normal. Yet they know about the volcano’s violent past.

Vesuvius last erupted in 1944. A giant cloud of ash rose from the volcano. Lava spilled down the mountain. Forty-five people died.

Even now, the volcano still quietly rumbles. It rattles the ground. It gives off gas. It spews bits of ash and rock. But it doesn’t explode.

Vesuvius may be fairly calm for now. That will not last forever. Major eruptions come about every 2,000 years. So scientists think it will roar to life again soon.

As a result, scientists watch Vesuvius carefully. They use scientific instruments to measure any volcanic activity. They want to predict future eruptions. They hope to give people plenty of time to escape the dangers of this mighty mountain.

Face of History. This statue from Pompeii shows someone trapped by the eruption.

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Wordwisearchaeologist: scientist who studies places and things from the past

composite volcano: steep–sided volcano made up of layers of ash and lava

excavate: to dig in a careful, scientific waylava: melted rock on Earth’s surfacemagma: melted rock under Earth’s surfaceplate: piece of Earth’s crust

Warning Sign? In 1944, the volcano had a small eruption, spewing hot ash into the air. Scientists hope this eruption was not a sign of things to come.

Asleep for Now. Three million people live near Vesuvius today. If the volcano wakes up, it will cause big problems for them.

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of what you already know about oil. connect it to new information as you read this article.

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by catherine fox

oil fuels your world. that means challenges

for your future.

PAUL RAPSON/PHOTO RESEARCHERS, INC.

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By Paul NicklenWildlife Photographer

Earth is heating up. That means

trouble for animals in the

Arctic.

Oil is part of nearly all of our lives. Whether you live in the United States, Kenya, or Brazil, you use oil. You even use oil in ways you would never guess.

Take skateboarding, for example. Picture yourself on a skateboard. You kick your board onto a curb to do a railslide. You think about keeping your balance as you glide along the curb. You should think about oil too.

You may wonder what oil has to do with your ride. To find out, tap your helmet. The helmet is plastic. So are your kneepads. Now flip your board over and look at the wheels. What are they made of? You guessed it—plastic. Many plastics are made from oil.

You may not have thought oil was part of skateboarding. You may not know that it is part of nearly everything you do. Do you eat? There may have been oil in the fertilizers that helped grow your food. Do you use roads? A sticky kind of oil is used to pave streets. Do you take medicine? Even some pills have oil in them!

Yes, we have an amazing thirst for this natural resource. A natural resource is something useful found in nature. Worldwide, people use more than 80 million barrels of oil a day. Each barrel is equal to 42 large milk jugs. That’s 3,360,000,000 jugs a day. Let’s look at how oil became so important.

Tiny ocean plants and animals died and fell to the seafloor.

The Origin of Oil

The story of oil began millions of years ago. Most scientists believe oil started with dead plants and animals. These pictures show how they turned into oil. Mud, dirt, and sand covered and pressed

down on the dead plants and animals. The pressure turned the plants and animals into oil. We now dig wells to reach the oil.

Oil–Based Products. We use oil to make plastic helmets, kneepads, and wheels.

Oil, Oil Everywhere! Everything in front of this family’s house is made from oil.

JOE MCBRIDE/GETTY IMAGES

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Early Days of OilThe oil we use today has been around for a long time. It actually comes from plants and animals that lived millions of years ago. When they died, their remains fell to the seafloor. Layers of dead things piled up.

Sand and dirt covered the layers of plant and animal remains. Ever so slowly, the sand and dirt turned to rock. The rock pressed down on the remains. It squeezed them together.

That turned the remains into oil. Most oil stayed underground. Some of the oil seeped up to the surface. Puddles of oil formed.

People began using oil they found in the puddles thousands of years ago. They burned the oil in lamps. They spread tar on their roofs to keep water out. Tar is a sticky kind of oil.

Those were about the only ways ancient people used oil. Things changed in the 1800s. That’s when people really started using oil.

Inventors found that they could separate oil into different chemicals by heating it to 400° Celsius (750° Fahrenheit). This process is called refining. People then used the chemicals to make a whole range of new products.

One of the products was a fuel called kerosene. People used it in lamps. The lamps helped people light their homes in the days before electricity.

Another product of refining is gasoline. It makes a great fuel for cars, which were invented in the late 1800s. Making gasoline is one of the main ways we use oil today.

Thirsty for OilSoon nearly everyone was buying a car. In 1900, about eight thousand cars bumped along roads in the United States. Just 20 years later, eight million cars zoomed down our roads.

Some people chose to buy cars before putting bathrooms in their houses. “You can’t go to town in a bathtub,” one woman explained.

Other inventors figured out how to make plastic from refined oil. Soon everything from forks to phones was being made from plastic.

To find all the oil we need, people drill deep into Earth. You can find oil wells all over the world. You can even find them rising from the ocean.

Pumping Away. Two–thirds of the oil that people use in the United States fuels cars, trucks, and airplanes. Plenty of Plastic. Beach balls, suitcases, and

candy machines are just a few of the plastic things made from oil or natural gas.

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Fueling the Future. Cars were invented in the late 1800s. They created a huge new demand for oil.

JaNuary-February 2008 2120 NatioNal GeoGraphic explorer

Facing the FutureToday, we use oil as if we had an endless supply of it. We don’t. Oil takes millions of years to form, and Earth only has so much of it. We’ve already used up a lot of Earth’s known oil.

That means we have to find oil in new places. Scientists are looking for other sources of oil. They’ve found oil trapped in sand. They’ve also found rocks that hold oil the way sponges hold water. Unfortunately, getting oil from sand or rock is very expensive.

Finding enough oil isn’t the only problem, though. Drilling for it can damage the environment. Ships carrying oil sometimes spill oil, harming wildlife.

Worse yet, burning oil puts harmful gases into the air. Too many of these gases cause the air to trap more heat than it should. That causes global warming. It is a worldwide rise in Earth’s average temperature.

Seeking SolutionsSo what do we do? For starters, we can practice energy conservation. That means using less energy. Doing so will help Earth’s oil supplies last longer.

People burn oil to make electricity. So one way to save oil is to use less power. Turn off TVs and computers when not in use. Switch to low-energy lightbulbs. People also burn oil to make heat. You can save oil by putting on a cozy sweater and turning the heat down a bit.

Scientists are also looking for new sources of energy. They are looking for ways to turn corn and other plants into fuels for cars. They want to use wind and sunlight to make electricity. Some scientists even want to use ocean waves to make power.

As you can see, fueling our future will be a challenge. Will we face a bumpy road or a smooth ride? That depends on the choices we make today.

energy conservation: using less energy

environment: the natural world on which all living things depend

gasoline: form of oil used in cars

global warming: worldwide rise in average temperature

natural resource: something useful found in nature

refining: heating oil to separate it into different chemicals

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Green Car. People are finding new, creative ways to replace gasoline. This car runs on used vegetable oil.

Wind at Work. Wind farms use wind power to make electricity.

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Coming in Marchcarved in Stone: Tour some of the geological wonders of the American landscape.

on the insect trail: Peer through a scientist’s camera at some of Earth’s wildest–looking bugs.

continental cats: Meet the fabulous felines of North America.

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