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00:00Rock and Learn!
00:19Hey, Tara!
00:20Hiya, Marco! What's up?
00:22My friend Kevin needs a little help studying for his Earth science test.
00:27Do you think you could pencil us in for a session?
00:31Well, I do know a thing or two about Earth science.
00:35And I hear that you're a real whiz at reviewing for science tests.
00:39Thanks, Tara!
00:40Kevin is already waiting for us at my super science station.
00:44Off we go!
00:58Marco! Tara! Boy, am I happy to see you!
01:02I need to get ready for my Earth science test.
01:05Glad to help, kid.
01:07Earth science is kind of my specialty.
01:10When you study Earth science, you learn about astronomy, geology, meteorology, and more.
01:17Let's start by talking about our solar system.
01:21Tell me what you know.
01:23Well, the Sun is in the middle of the solar system, and it provides us with light and heat.
01:29Good, good! You know anything else?
01:33There are eight planets that orbit the Sun, but I always have trouble remembering their order.
01:39I know a fantastic way to remember the order of the planets.
01:46Hello? Who's calling?
01:50Professor who?
01:54Oh! You're Kevin's mom!
01:58His snack is ready?
02:00Okie dokie, we'll be right there!
02:03Great news! Kevin's mom would like to serve us a little snack.
02:07Sounds good to me!
02:15So, Kevin, I didn't know that your mother was a professor.
02:18Oh, yes. She's very educated.
02:21Here you go! Enjoy!
02:23Oh my! What just happened?
02:26My very educated mother just served us nachos!
02:29That's it! That's the order of the planets!
02:33Huh? I see what he's getting at.
02:36Take the first letter of each word in the sentence,
02:39My very educated mother just served us nachos.
02:48And now we'll give you the first letter of the name of each planet.
02:52My Mercury
02:55Very Venus
02:58Educated Earth
03:01Mother Mars
03:03Just Jupiter
03:06Served Saturn
03:09Us Uranus
03:12Nachos Neptune
03:15My very educated mother just served us nachos.
03:20Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
03:27Exactly!
03:29My very educated mother just served us nachos.
03:35Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
03:41Hey, that's pretty cool! That makes it easy to remember the planets.
03:45Great! Now back to the Solar System Learning Center at my super science station.
03:51But what about the...
04:00Ah, the nachos!
04:03Tough going, kid.
04:05But nachos aren't the only things in life.
04:08And the planets aren't the only things that orbit the Sun.
04:12Take a look at this.
04:14Wow! That's pretty cool, Tara!
04:18What are all these chunks of rock between Mars and Jupiter?
04:22That is known as the asteroid belt.
04:26The objects in this area range in size from dust particles all the way up to Ceres,
04:32which is 900 kilometers in diameter.
04:36Ceres is actually considered a dwarf planet because it has a large enough mass to have a rounded shape.
04:43But as you can see, it's not large enough to have cleared its orbit around the Sun.
04:48By that I mean there are other objects in the same orbit with Ceres.
04:54All of those other chunks of rock and metal are known as asteroids.
04:59Is Ceres the only dwarf planet?
05:02Nah, we've got more.
05:04Every so often, a group of professional astronomers from around the world meet to assign names to objects in space.
05:12Three dwarf planets they've named are Ceres, Pluto, and Eris.
05:19Looks like there's another asteroid belt further out.
05:23That's called the Kuiper belt.
05:28Whoa! What's that?
05:30Oh, that's a comet.
05:32Comets are collections of ice, dust, and small particles of rock.
05:37Most have long, oval orbits.
05:40When they pass near the Sun, their ice melts and evaporates.
05:44People on Earth see comets as huge, glowing balls with tails made of gas or dust trailing millions of miles behind them.
05:53All of this is pretty cool, but how does it fit into Earth science?
05:59Learning about the solar system is important for Earth science because what happens in space affects things on Earth.
06:06For example, let's take a closer look at how the Earth and Sun interact.
06:12See how the Earth goes around or orbits the Sun?
06:18Yeah, Marco, I remember that from science class.
06:21It takes a full year for one revolution around the Sun, and that's what causes our seasons.
06:27Explain to me how the Earth's orbit causes the seasons.
06:32Well, I know it has something to do with the tilt of the Earth, but I never really understood that part.
06:38Hmm, let me see if I can help.
06:41When does the Sun feel warmest, early in the morning or around noon?
06:46It's warmest around noon.
06:48Correct. That's because the Sun's rays are more direct around noon.
06:53In the morning, when it's cooler, the Sun's rays are more indirect.
06:58So, the Earth flips back and forth?
07:01Oh, no, no, no, no, no, no. The Earth keeps pretty much the same tilt, but watch as she moves around the Sun.
07:10See? Here the northern hemisphere gets more direct Sun, so it is summer there.
07:16And since the southern hemisphere gets the indirect light, it's winter?
07:21Now you've got the idea.
07:23If we keep moving around until we get over hereтАж
07:28Then it's summer in the southern hemisphere and winter in the northern hemisphere.
07:33Wow! Actually seeing it in action makes it easier to understand.
07:37Then take a look at this.
07:39See how the Earth rotates on its axis?
07:42It goes around once every 24 hours.
07:45And that's what causes day and night.
07:48The parts of Earth facing the Sun are in daylight.
07:51As the Earth rotates, the Sun seems to set in the west.
07:56Super! I think you've really got a good idea about how things work in our solar system.
08:02Here, take one of these, kiddo.
08:05Tara, I don't think it's going to be raining anytime soon.
08:09Inside the science stationтАж
08:12I wouldn't be so sure.
08:14It looks like a flash flood!
08:30We got here whether or not you wanted to!
08:34Oh, brother!
08:36Here at the Water Cycle and Weather Learning Center,
08:39we'll learn how the water cycle affects weather on Earth.
08:43The Sun provides the energy that drives the whole water cycle.
08:48As the Sun heats water on Earth, water evaporates into the air.
08:53As the water vapor cools in the atmosphere,
08:56it condenses into small water droplets that form clouds.
09:01When the water droplets get too heavy, they precipitate back to the ground.
09:06Then the water accumulates in aquifers, rivers, lakes, and the oceans.
09:11And the whole thing can start all over again!
09:16Water turns to vapor
09:20by evaporation.
09:24Clouds form slowly in the sky
09:28by the process of condensation.
09:33When the droplets get too heavy,
09:37they fall as precipitation.
09:41Rain or sleet or snow that melts,
09:45then comes accumulation.
09:50Evaporation!
09:54Condensation!
09:58Condensation!
10:02Precipitation!
10:06Accumulation!
10:10Okay, I think I understand how the water cycle works.
10:14But why does it rain and snow places other than over the water?
10:18Good question!
10:20We get rain and snow and other precipitation in all kinds of places
10:25because the sun heats the earth unevenly.
10:28Land heats and cools faster than water.
10:31And we know that it's warmer near the equator than the poles.
10:35All of this uneven heating keeps cold and warm air moving
10:39and makes changes in air pressure.
10:42Here's how those air pressure changes cause wind.
10:47Cold air weighs more than warm air,
10:50so the pressure of cold air is greater.
10:53When the sun warms the air,
10:55the air expands, gets lighter and rises.
11:02Cooler, heavier air moves to where the warmer and lighter air was.
11:07In other words,
11:08wind usually blows from areas of high air pressure
11:11to areas of low air pressure.
11:14Now, warm air can hold more water vapor than cold air.
11:18So as the air gets colder,
11:20you get condensation and then precipitation.
11:24There you go!
11:25But it is the temperature of the air
11:28that determines the kind of precipitation.
11:31Rain happens when drops of liquid water fall on the surface of the earth.
11:36Snow forms when the air is so cold
11:39that water vapor turns directly into ice
11:42without ever passing through a liquid state.
11:45If the air is cold enough,
11:47the snow will fall all the way to the ground.
11:50Otherwise, it might melt into rain on its way down.
11:55Sleet refers to water droplets
11:58that freeze on their way down through really cold air.
12:02Unlike snow,
12:03sleet goes through a liquid state before freezing.
12:07The result is that sleet is not light and fluffy.
12:11Hail is like mega-sleet.
12:17When it hails, large balls of ice fall from the sky.
12:22Hail forms in a more complex way than sleet.
12:26As ice crystals start to fall,
12:29wind carries them back up high into the clouds.
12:32This happens over and over,
12:35and the crystals grow each time.
12:37Eventually, they get too heavy and fall hard.
12:42That's wild, Tara!
12:44I never knew weather could be so complex!
12:47And that's just the surface, kid.
12:49But it's enough to get you started.
12:52Ooh!
12:53Those nachos aren't setting so good.
12:55Are you okay?
12:56She'll be fine,
12:57but I'm a little worried about us if there's an...
13:01Earthquake!
13:12Ah!
13:13I feel much better now.
13:15Uh, that's nice.
13:17But where are we?
13:20Just where we should be,
13:22in the Geology Learning Center.
13:24This is where we can learn about different kinds of rocks
13:27and how they are made.
13:29Take a look at all these layers of rocks.
13:32Little bits of earth were washed downstream.
13:35They settled to the bottom of a river,
13:38lake, or ocean.
13:40Layer after layer was deposited on top
13:43so they were pressed down more and more.
13:46Over time, the layers turned into a type of rock
13:49called sedimentary rock.
13:52That's right.
13:53Sedimentary rocks make up about three-quarters
13:56of the rocks at the Earth's surface.
13:58Sometimes they can give us clues
14:00about what the environment was like
14:02when those rocks were formed.
14:04How can they do that?
14:06Well, sometimes dead plants or animals
14:09get buried in the sediment.
14:11They get covered up by new layers of sediment
14:14and sometimes become fossils.
14:16Some fossils are actually parts of an animal
14:19like its teeth or bones that have turned into stone
14:22or fossilized.
14:24Others are trace fossils like dinosaur footprints
14:27or tunnels made by worms.
14:30But most fossils are casts.
14:33Most fossils are casts.
14:35The dead plants and animals decay
14:38after the sediment is turned into rock,
14:40leaving behind a hollow mold.
14:43Salts or other minerals can fill the cast
14:46and hold its shape.
14:48Fossils found in the same layer of sedimentary rock
14:51are from things that lived around the same time.
14:54As new layers form on top,
14:57the fossils get buried deeper and deeper.
15:00I think I understand.
15:02So the deeper the fossils are found,
15:05the older they are?
15:06You've got it!
15:08And sometimes large amounts of plants
15:10are deposited in sedimentary rocks.
15:13If they are compressed under a lot of pressure
15:16for a long period of time,
15:19they turn into carbon.
15:21This gives us coal, oil, natural gas, and petroleum.
15:26I guess that's why they're called fossil fuels.
15:29You bet it is.
15:30And let me tell you,
15:31fossil fuels are really a...
15:34gas!
15:37Oh, brother.
15:40Okay, sedimentary rocks make up about
15:43three-quarters of the rocks at Earth's surface.
15:45You got it!
15:46What about the rest of the rocks?
15:48What are they?
15:49Glad you asked.
15:51There are two other kinds of rocks,
15:53igneous and metamorphic.
15:56Igneous rocks form when molten rock cools
15:59and becomes solid.
16:01Molten rock is called magma
16:03when it is below the Earth's surface.
16:06But sometimes magma pushes up through cracks
16:09to the surface of the Earth.
16:11Then it is called lava.
16:13I just love a good eruption!
16:17Stop that!
16:19When lava cools,
16:21it becomes a kind of igneous rock
16:23called volcanic rock.
16:25Basalt is the most common type of volcanic rock.
16:29Most of the rocks on the ocean floor are basalt.
16:33Igneous rock can also form
16:35when magma cools slowly
16:37and becomes hard while it's deep underground.
16:40Rocks that form this way, like granite,
16:43usually have large crystals.
16:46Fossils are not usually found in igneous rocks.
16:50The heat of a volcanic eruption
16:52tends to destroy living things,
16:54and only rarely preserves any evidence of them.
16:58However, fossils may be found
17:00in volcanic ash deposits,
17:02which are actually a kind of sedimentary rock.
17:06That makes sense.
17:07Sedimentary rocks are made from sediment,
17:10and igneous rocks are made when molten rock is cooled.
17:14But what about metamorphic rocks?
17:16How do they form?
17:18Good question, kiddo!
17:20Metamorphic rocks are rocks
17:22that have morphed, or changed,
17:24from one kind of rock into another.
17:27Metamorphic rocks were once igneous or sedimentary rocks,
17:31but movement of the Earth's crust caused them to change.
17:36Just moving the rocks changes them?
17:38No.
17:39Try pushing your hands together very hard.
17:44Do you feel heat and pressure?
17:47Yeah.
17:49When the Earth's crust moves,
17:52igneous or sedimentary rocks get squeezed by tremendous pressure,
17:58which heats the rocks and pulls them like taffy.
18:02The original rock is changed by this heating and pulling,
18:06and it becomes a metamorphic rock.
18:09As you might guess,
18:11any fossils that were in the sedimentary rock
18:13will now be in the metamorphic rock.
18:16But those fossils may be stretched and deformed
18:19because of the heating and pulling.
18:22Bummer!
18:23Metamorphic rocks are the least common of the three kinds of rocks.
18:28Slate and marble are two examples.
18:31Wow, that really rocks!
18:38Whoa, what's this?
18:40A rock concert?
18:42As a matter of fact, it is!
18:44Ladies and gentlemen,
18:46please welcome all the way from Little Rock, Arkansas,
18:51the Pet Rocks!
18:56All right!
19:01Sedimentary
19:06Igneous
19:09And metamorphic
19:14Three kinds of rocks
19:18Three kinds of rocks
19:22Sedimentary
19:24Yeah!
19:26Igneous
19:30And metamorphic
19:34Three kinds of rocks
19:38Three kinds of rocks
19:45Even though two rocks may be formed the same way,
19:49they can be made up of different kinds of minerals.
19:52That's right!
19:53To identify the minerals in rocks,
19:56scientists use properties like color,
19:59luster,
20:00hardness,
20:01and streak.
20:03Look at these!
20:05I wonder what minerals they are.
20:07Hey, if I describe their properties,
20:10that might help me to identify them.
20:13Bravo!
20:14Now, the color of a mineral is the first thing people tend to notice.
20:18But be careful!
20:20Most minerals can occur in more than one color.
20:24Luster describes how light is reflected from the surface of a mineral.
20:29The two main types of luster are metallic and non-metallic.
20:35The hardness of a mineral is its ability to resist scratching.
20:40The Mohs hardness scale uses 10 minerals to rank hardness.
20:45Take a look here!
20:47A diamond is the hardest naturally occurring substance
20:51with a hardness of 10.
20:53And talc is very soft,
20:55so it only has a hardness of 1.
20:58That's all good and fine,
21:00but how can I find out the hardness of the minerals in this box?
21:03With a little scratching.
21:07Not that kind of scratching!
21:09We'll use minerals and objects from the Mohs scale.
21:13If your mineral sample can scratch an object,
21:16say, this penny,
21:18then it has a higher hardness.
21:21Let's try this one!
21:24Good choice!
21:26I like the nice metallic luster.
21:29Can it scratch a penny?
21:32Can it scratch a penny?
21:35Looks like it does, Marco!
21:37That means this mineral has a hardness higher than 3.
21:41That's the way to do it!
21:43Now try scratching this quartz.
21:46Nope!
21:47And look!
21:48The quartz will scratch my mineral sample,
21:51so it has a hardness between 3 and 7.
21:55We could keep on scratching away with different materials
21:59from the Mohs scale to narrow it down even more,
22:02but I think you get the idea.
22:04I sure do!
22:05Thanks, Tara!
22:06Another way to categorize minerals with a hardness lower than 7
22:10is to determine their streak.
22:13Streak?
22:15Does that mean some of them have racing stripes?
22:18Nah!
22:20The streak of a mineral is the color of the powder it leaves
22:24when you scrape it across a streak plate.
22:27We know your mineral has a hardness lower than 7, so...
22:32Red?
22:34That's not what I would have guessed at all!
22:36Don't feel too bad, kid.
22:38Science is full of surprises.
22:41Have a look at this table here.
22:43Do any of those descriptions match your mineral?
22:47Let me see.
22:49Steel gray,
22:51hardness 5.5 to 6.5,
22:55rust red streak,
22:57metallic luster,
22:59I'll bet this is hematite!
23:02That's the way to do it!
23:04Great job!
23:08Well, kid, your earth science knowledge is really building up.
23:13It looks like something else is building up under my chair.
23:17Hey, that sort of looks like a volcano!
23:26I guess it was a volcano.
23:29And just look where it brought us!
23:32Ah, the topographic learning center!
23:35This is the perfect place to learn about how the surface of the earth changes.
23:40Seems like a volcano would be pretty good at changing the surface.
23:44Tell me about it, kid.
23:46These aren't pimples, you know.
23:49I had a friend do a science fair project on volcanoes.
23:53She told me there are several types.
23:55She told you right!
23:57There are shield volcanoes,
23:59cinder cones,
24:00stratovolcanoes,
24:02and more!
24:03That's a lot of volcanoes!
24:05So, what's the difference between the types?
24:08Shield volcanoes are built by layer upon layer of lava.
24:12Their eruptions travel great distances from a central event or group of events,
24:18so they have broad, flat, rounded shapes.
24:21They kind of look like a shield lying on the ground.
24:24That's a great way to remember the name!
24:27But while they may look flat from above,
24:30they can still get pretty tall.
24:32Mauna Loa is the largest shield volcano.
24:36Mauna Loa means long mountain,
24:40but it stands over 13,000 feet above sea level,
24:44and it rises over 28,000 feet from the ocean floor.
24:49It would be the world's tallest mountain if it weren't mostly underwater.
24:54Maui, wowie!
24:56Actually, it's on the Big Island of Hawaii.
25:03The eruptions of shield volcanoes usually don't have much ash,
25:07and they are fairly safe for scientists to monitor.
25:10But some other kinds of volcanoes can throw hot ash and cinders into the air.
25:17These can form a pyroclastic flow,
25:20which travels very fast and burns almost everything in its path.
25:24That's the truth.
25:26The temperature of a pyroclastic flow can reach over 500 degrees Celsius.
25:32Whoa! What kind of volcano can do that?
25:36Stratovolcanoes can.
25:38They are quite beautiful, like yours truly.
25:42But they tend to be tall and symmetric with steep sides.
25:47A few stratovolcanoes that you might have heard of are
25:51Mount Fuji in Japan,
25:53and in the U.S.A.,
25:55you'll find Mount St. Helens and Mount Rainier in Washington State,
26:00and Mount Hood in Oregon.
26:06Not Oregon, Oregon!
26:10Those stratovolcanoes really are beautiful.
26:13What about cinder cones?
26:15Ah, the little guys.
26:17You can often find cinder cones on the flanks of shield volcanoes and stratovolcanoes.
26:23When a cinder cone volcano erupts,
26:26cinders of lava are blown into the air and fall around the opening of the volcano.
26:32The pile of cinders forms a small, oval-shaped volcano
26:36that can grow to about 1,000 feet.
26:39But some are much smaller.
26:41Many cinder cone volcanoes have a bowl-shaped crater at the opening.
26:50Hey, Marco!
26:52What causes volcanoes in the first place?
26:55To explain that, let's dig a little deeper.
26:58Deeper into the Earth, that is.
27:00Earth is divided into four layers.
27:03The solid inner core,
27:06the liquid outer core,
27:08and the mantle.
27:09That's the thickest layer.
27:11And last, and least, is the crust.
27:15Least, because it's the thinnest layer.
27:18The rocky outer crust is made of plates that fit together sort of like puzzle pieces.
27:25These plates move a little bit each year
27:28as they slide on top of a weak layer of the mantle.
27:32This hotter, deeper layer of the mantle can be pushed and pulled like putty.
27:38The whole process is called plate tectonics.
27:42The edges of the Earth's plates touch each other.
27:45As they move, the plates may just slide past each other.
27:49But the plates can also spread apart
27:52or even crush together.
27:55Sometimes, when two plates collide,
27:58large mountain ranges, such as the Himalayas, are formed.
28:02That happens if the two plates have the same density,
28:06so they fold as they move together,
28:09much like two kitchen rugs push together.
28:13That explains mountains.
28:15But I wanted to know how volcanoes are formed.
28:18Hold your horses, kid.
28:21If colliding plates have different densities,
28:24one plate can be forced back down into the deeper regions of the Earth.
28:29That plate can begin to melt when it reaches a depth which is hot enough.
28:34The molten crust rises back towards the surface
28:38where it helps make volcanoes and islands.
28:41Phew! That's a long process.
28:43Is that how all volcanoes are formed?
28:46Well, no.
28:48Here's another way.
28:50As the plates move, hot spots under the crust may find weak places in the plates
28:55or between two plates that are moving apart.
28:58This will allow magma to come to the surface from deep within the Earth.
29:03The result is a volcanic eruption
29:06which can add new landmass to existing land
29:09or even form new islands.
29:12Okay, let me get this straight.
29:15Volcanoes can form where the plates are pushing together,
29:19where they're pulling apart,
29:21or anywhere the Earth's crust is weak.
29:23That's the way the cookie crumbles.
29:26And the Earth's crust, too.
29:29I cracked myself up.
29:32That's a good one.
29:33Oh, Marco.
29:37Now that you have an idea of how Earth's surface can be built up,
29:42let's talk about how it can be worn down.
29:46Weathering is the process that causes rocks to crack and fragment.
29:51Since rocks form in different ways
29:54and are made up of different minerals,
29:57they react differently when exposed to temperature changes,
30:01moisture, particles in the air, or pressure changes.
30:05I suppose that means there are different kinds of weathering.
30:09That's right, Kevin.
30:11One thing that causes weathering is frost.
30:14When water freezes, it has an unusual property.
30:18Unlike most materials that contract when they are cooled,
30:22water expands when it solidifies into ice.
30:27This can put incredible pressure on rocks.
30:30Water gets into the pores or cracks of the rocks and then freezes.
30:36So when the water freezes,
30:38it expands and causes pieces of the rock to break off.
30:42Right.
30:43Another kind of weathering is abrasion.
30:45That can happen when rocks rub against each other,
30:48like when a rock rolls downhill or when it tumbles in rivers.
30:54Wind can cause abrasion, too.
30:56Wind sometimes carries dirt or sand that can wear down rocks as it blows against them.
31:03Plants like moss and lichen can wedge their way into pores, crevices, and cracks in rocks.
31:10Seeds from other plants can get into crevices, too.
31:13As they grow, they cause the rocks to crack apart.
31:18I heard that wetting and drying of rocks can make them break up.
31:22Oh, yes.
31:23The combination of wetting and drying is very effective at breaking up clay.
31:28That's because clay swells when it gets wet and then shrinks and crumbles as it dries.
31:36Oh, I get it.
31:37The process of wetting and drying only weathers some kinds of rocks.
31:42Sometimes rocks break down because the minerals they are made of react with chemicals in water or air.
31:49For example, carbonic acid is created when carbon dioxide dissolves in water,
31:55and this acid can dissolve limestone and eventually cause the formation of caves and caverns.
32:02Oh, look at the stalactites and stalagmites.
32:06You're a regular little spelunker, huh?
32:10Stalactites hold tight to the ceiling of the cave, and stalagmites might reach the ceiling someday.
32:18What a smarty!
32:20Now, erosion is simply the moving of sediments or rock particles.
32:25Moving water is the most powerful force of erosion on Earth.
32:30The world's rivers deliver about 20 billion tons of sediment to the oceans each year.
32:37That's a lot of erosion!
32:40And that's why you can see fan-shaped deltas at the mouths of some rivers, such as the Nile.
32:46V-shaped valleys, canyons, and gorges are also carved by streams and rivers flowing through the mountains.
32:54Moving air, or wind, is another important mover of sediment, especially in dry regions.
33:03When tiny sand grains are lifted and carried by the wind, they can sculpt rocks into a variety of shapes.
33:12Sand dunes are hills of sand deposited by the wind, such as those at Great Sand Dunes National Park in Colorado.
33:21But of all the things that cause erosion, my favorite is a glacier.
33:28Glaciers form when snow piles up over time and turns to ice.
33:33The glacier begins to flow outwards and downwards under the pressure of its own weight.
33:39Like great rivers of ice, glaciers have sculpted mountains and carved out U-shaped valleys.
33:47Valley glaciers flow down valleys.
33:50And continental glaciers, such as the ones on Greenland and Antarctica, blow outward in all directions.
33:59Glaciers reshape the underlying and surrounding landscape as they move, by eroding rock from one place and depositing it in another.
34:10That's called deposition.
34:12Glaciers, rivers, and wind are major forces of deposition that can build up the Earth in some places.
34:20And I think I've got the scoop on erosion.
34:24Erosion is when the Earth is worn down.
34:27It can happen because of water, wind, or ice.
34:31That's right, kid.
34:32Weathering and erosion work together to reshape the surface of the Earth.
34:38Water and cracks of rocks can turn to ice in the winter and make the cracks bigger.
34:45Over time, bits and pieces of the rock break off and fall away.
34:51Wind can pick up these small bits and wear down weaker parts of rock.
34:57Rain can wash the small bits away.
35:00Over time, these processes can work together to leave interesting formations,
35:05such as the arches in Utah or the hoodoos in Bryce Canyon.
35:11Canyons look like fun places.
35:14I'd like to travel to see them someday.
35:16Well, right now we need to travel to our next learning center.
35:20Right this way.
35:22Whoa!
35:26Hey, wait, Marco.
35:28I think my chair ran out of gas.
35:31Uh-oh.
35:32Looks like we need an alternative energy source.
35:35Don't worry.
35:36Balance this on your head.
35:38Okay, but how will this solar panel help?
35:42We're indoors.
35:44Just you wait and see.
35:50Woo-hoo!
35:54Yeah!
35:56Hiya, boys.
35:58I see you used a perpetual resource to get here.
36:02Perpetual resource?
36:04Yep.
36:05A perpetual resource is one that cannot be affected by human use.
36:10Perpetual resources are also called inexhaustible resources.
36:16They include things like solar energy that can be converted into electricity.
36:22Solar energy can also be used to heat water or air for homes and businesses.
36:27Sounds like we should use solar energy for everything.
36:32Well, solar energy is very dependent on the time of day, the time of year, and the weather.
36:38So, in order to be efficient, a large surface area is required to collect the energy from the sun.
36:45But scientists are working on ways to get around that.
36:48Hmm.
36:49Is solar energy the only perpetual resource?
36:53Oh, no.
36:54There's always the wind.
36:56Remember that the wind is caused by uneven heating of Earth by the sun, so it's an indirect form of solar energy.
37:04The wind blows stronger and more consistently in some areas.
37:08Wind turbines and wind farms can be built in those places to convert the wind energy into electricity.
37:16And there's also geothermal energy.
37:19Heat from the Earth can be used to make steam or hot water to heat buildings or generate electricity.
37:26Some scientists are even looking at ways to utilize the oceans to produce energy for us without causing any environmental damage.
37:35They've come up with a few ways of tapping the energy from tides and waves.
37:40We might even find a way to use temperature differences in the ocean to produce energy.
37:46But in some regions, the surface water can be 40 or more degrees Fahrenheit warmer than the deep water.
37:53So, perpetual resources include solar, wind, geothermal, and ocean energy.
38:00What other kinds of resources are there?
38:02Glad you asked, kiddo.
38:04There are renewable resources and non-renewable resources.
38:09I've heard of renewable resources.
38:12They can be replenished as fast or faster than we use them.
38:15That's true.
38:17But the problem is that usually the demand for resources like wood, crops, soil, and water increases over time.
38:27If the demand gets too high, these resources cannot be replenished fast enough.
38:33We have to be careful and keep things in balance.
38:36That does sound like a good thing to do.
38:39And what about non-renewable resources?
38:41I guess those can't be replenished at all.
38:44When they're gone, they're really gone.
38:47Non-renewable resources like natural gas, oil, and coal that we get from fossil fuels will eventually run out if we keep using them.
38:56Energy efficiency and conservation are so important.
39:01We need to make non-renewable resources last as long as possible while we are looking for new alternatives.
39:09Energy efficiency is the use of technology to perform the same function with less energy.
39:16Like putting tinting on your windows to keep out the sunlight that heats up buildings in the summertime.
39:22No, that's to make it look cool.
39:24Sorry.
39:26Energy conservation is any behavior that causes us to use less energy.
39:32Like turning off lights when they're not being used.
39:35Exactly, Kevin.
39:36And by using energy efficient light bulbs, you can save a lot on your electric bill.
39:42Another way to conserve energy is by insulating and weatherizing homes and buildings.
39:48That way you use less air conditioning and heating.
39:51You can also save on heating and cooling by placing trees, shrubs, or other landscaping to block the wind and provide shade.
40:01But we can conserve other resources besides just energy, such as wood and water.
40:09There are many ways to help save water around the house.
40:13Turn off the water while you're brushing your teeth.
40:16Take short showers instead of baths.
40:19And be sure to fix any leaks.
40:21I worked with my mom to convince the people in our neighborhood to find a garbage service that recycles.
40:27We separate out plastic, glass, aluminum cans, and paper for recycling.
40:32Excellent!
40:34By recycling, you are not only conserving resources, but you are also helping to keep unnecessary garbage out of landfills.
40:42Yeah, thanks for helping to keep the Earth a cleaner place to live, kiddo.
40:47You're welcome, Tara.
40:48And thanks to both of you for helping me study Earth science.
40:52I'm ready to ace my test.
40:54I'm so proud of you.
40:57Well, I should be getting back home, Marco.
40:59I'm ready to teleport.
41:01Okey-dokey.
41:09Huh?
41:15Oh, Marco.
41:20Hey, science fans!
41:23To quiz yourself on Earth science, you can download a practice test at my website.
41:29Just visit www.marcodepencil.com.
41:34Ciao!
41:41Now that we've reviewed some of the material from Earth science, let's see how well you might do on a practice test.
41:48For those of you following along, you might want to use pause when the question first comes up to see if you can choose the right answer before Kevin.
41:57Let's begin with some questions about the solar system.
42:031. Look at the diagram of our solar system below.
42:07What is the name of Planet 5?
42:11Oh, yeah, Marco.
42:13My very educated mother just.
42:17That starts with J, Jupiter.
42:19That's answer B.
42:21Fantastico!
42:23Sometimes you might be asked to fill in your answer right on the page with the questions.
42:27But this test has a separate answer sheet.
42:31Be sure to ask your teacher how you're supposed to mark the answers on your test.
42:37Let's put the test over the answer sheet just under the question we are answering.
42:42That way we can make sure we fill in the right bubble.
42:512. Which objects in our solar system have long tails when they are close to the Sun and are made mostly of rock and ice?
42:59A. Planets
43:01B. Asteroids
43:03C. Dwarf planets
43:05D. Comets
43:07The only one of these things I remember having tails are the comets.
43:12You have a great memory.
43:15Our answer is D.
43:233. What causes day and night on Earth?
43:27A. Sun
43:29B. Earth
43:32A. The Earth orbits the Sun
43:35Nah.
43:36Earth orbiting the Sun combined with the tilt of the Earth's axis is what gives us seasons.
43:42Not day and night.
43:45B. The Moon orbits the Earth
43:48The Moon orbiting the Earth causes the tides to rise and fall on the Earth.
43:53But it doesn't cause day and night.
43:57C. The Earth rotates on its axis
44:01I think this is the right answer.
44:04Right you are.
44:07C. The Sun lights up half of the Earth
44:10The parts that are in the sunlight are experiencing a day.
44:14The parts that aren't in the sunlight are experiencing night.
44:19And if we could look down at the Earth from the North Pole,
44:24we would see that the Earth is rotating counterclockwise.
44:28So the Sun seems to come up in the East and set in the West.
44:33Maybe I should check this last answer just to make certain C is the best choice.
44:38Good thinking, Kevin.
44:40D. The Sun orbits the Earth
44:44That's ridiculous.
44:46Everyone knows that the Sun doesn't orbit the Earth.
44:50That means our answer is C.
44:52The Earth rotates on its axis.
45:01Let's move on to questions about the water cycle and weather.
45:074. What supplies the energy to drive the water cycle?
45:12Can you remember what I told you?
45:14I remember, Tara.
45:15You said the energy source that drives the whole water cycle is the Sun.
45:21You're really starting to get on my good side.
45:25Okay, so our answer is A. Sun.
45:31Great job.
45:36Now let's see if you can get this next one.
45:385. The picture shows a place where air currents will form due to the uneven heating of the Earth.
45:45In which direction will air currents most likely move?
45:49Let's see.
45:51Warm air rises and the cool air will come in to replace it.
45:55So, A. From the lake toward the land.
45:59Looks right, but let me check all the answers.
46:03B. Straight up above the lake.
46:05B. Straight up above the lake.
46:08No, that's not right.
46:11C. From the land toward the lake.
46:14That's backwards.
46:17D. All of the above.
46:19That can't be right.
46:22So our answer is A.
46:30I'm glad that you look at all of the answers carefully.
46:34Some students make the mistake of choosing all of the above every time it's an answer choice.
46:40Not our boy. He's too smart to do something like that.
46:44Aw, thanks, Tara.
46:46Now, do you remember anything from the Geology Learning Center?
46:51I sure do. Sedimentary rock is formed in layers and the deeper the layers, the older they are.
46:58That ought to make this next question pretty simple.
47:036. The rock column above shows the layers in a sedimentary rock formation.
47:09The three core samples to the right were taken from the rock column on the left.
47:14According to this information, which fossil is the oldest?
47:19Well, the deepest layer is layer 1, so it is the oldest.
47:24Since the fossil on the bottom of core sample X came from layer 1, it is the oldest fossil.
47:31So the answer is C.
47:34Super!
47:39Let's see if you can get the answer to this next geology question.
47:457. Why are most fossils found in sedimentary rocks?
47:50Let me read through the answers.
47:53A. Fossils can be distorted in metamorphic rocks.
47:57That's true.
47:58You bet it is!
48:00Metamorphic rocks are made by pressure and heat on other types of rocks.
48:05That could really mess up any fossils in the rock.
48:09But let's look at all the answer choices.
48:12B. Igneous rocks were too hot when they formed.
48:16Considering that igneous rocks were made of molten rock, I'm sure they were too hot to preserve any fossils.
48:22What about C?
48:24Sedimentary rocks are best for preserving organisms.
48:28This one's also true.
48:30So the answer must be D, all of the above.
48:34Great job!
48:42You're a real gem.
48:45We'll take a look at one more geology question.
48:488. The chart below shows part of Moe's hardness scale for minerals.
48:53A student is testing an unknown mineral for hardness.
48:57The unknown mineral is tested against fluorite, but neither mineral scratches the other.
49:02Which of the following conclusions can the student accurately make?
49:07If the unknown mineral didn't scratch fluorite, and fluorite didn't scratch the unknown mineral,
49:13If the unknown mineral didn't scratch fluorite, and fluorite didn't scratch the unknown mineral,
49:17they both must have a hardness of 4.
49:20Keep that in mind while we look at the possible answers.
49:25A. The unknown mineral and orthoclase will not scratch each other.
49:30Orthoclase is harder than fluorite.
49:33So orthoclase would scratch the unknown mineral.
49:37A is wrong.
49:39B. The unknown mineral will scratch calcite.
49:43That's true.
49:44Yup, calcite is lower on the hardness scale.
49:48But let's not be too hasty.
49:50Read the last two answer choices.
49:54C. The unknown mineral will scratch orthoclase.
49:58That's the exact opposite of what would happen.
50:02D. The unknown mineral will not scratch gypsum.
50:06That doesn't seem right.
50:08No way.
50:09Gypsum is even lower on the hardness scale than calcite.
50:14So our answer is B.
50:22This kid has a mountain of information in his head.
50:26You think so?
50:27Let's see if he remembers what was said about Earth's changing topography.
50:339. Mountains may be formed when
50:36A. Volcanoes erupt.
50:38That's true.
50:39Some of the volcanoes even have the word mount in their name, like Mount Fuji.
50:44But I remember that mountains are formed other ways, too.
50:48Let me check the rest of the answers.
50:51B. Plates of the Earth's crust collide.
50:54That's true, too.
50:55Terra said the Himalayas were formed that way.
50:58Great memory, kid.
51:00Hmm.
51:02C says both A and B.
51:05And D says none of the above.
51:08So I'm gonna have to say that C is the right answer.
51:13Perfecto!
51:2010. Which of these processes can be caused by movement of the Earth's plates?
51:26Let's see.
51:27The highest mountain range in the world, the Himalayas, were formed by plates colliding.
51:33And the islands of Hawaii were formed because of a plate moving over a hotspot.
51:38Some of those islands still have volcanic eruptions.
51:42That makes all of the answers true.
51:46So our answer is D.
51:48All of the above.
51:56Let's see what you remember about weathering and erosion.
52:0111. Moving water was the most important factor in forming which of these?
52:07A. Sand dunes at Great Sand Dunes National Park.
52:11No, Terra said those were formed by wind.
52:15B. The Grand Canyon.
52:17I'm pretty sure that was formed by a river.
52:20Although I don't know what the name of the river is.
52:23That would be the Colorado River.
52:27C. The Andes Mountains.
52:29From what we discussed, mountains are built from volcanic eruptions or plate tectonics, not moving water.
52:36You've got a good head on your shoulders, kid.
52:40D. Kilauea Volcano.
52:42That's made out of flowing lava, not moving water.
52:46So the answer is B. The Grand Canyon.
52:49Nice work!
52:52Ooh, that's a nice picture.
52:55I'd like to go there someday.
52:58And the man at the bottom of the picture gives you some perspective as to how large the arch really is.
53:05All right, all right.
53:07Let's get down to business.
53:09Read the question, please.
53:1212. The land formed below is an arch found in Arcturus.
53:1712. The land formed below is an arch found in Arches National Park in Utah.
53:23Which type of weathering or erosion is not responsible for shaping this arch?
53:29Here's one of those questions that has to be read carefully.
53:33The word not makes a big difference in the answer I'll choose.
53:37Let's see.
53:38Tara talked about the combination of water, ice weathering, and wind all playing a part in forming arches.
53:46So I think the answer is A. Glaciers.
53:50Because glaciers did not help shape the arch.
53:54Right you are.
54:01You're a smart kid.
54:03So let's see how bright you are when it comes to energy and resources available on Earth.
54:09No problem.
54:1213. Which of the following is a renewable resource?
54:16A. Tree.
54:18That's renewable as long as we don't use them faster than new trees can grow.
54:22I think this is the answer.
54:24But I'll check them all to be sure.
54:27I'm so glad you have good test-taking skills.
54:31B. Natural gas.
54:34That's a non-renewable resource.
54:37C. Solar energy.
54:39Ah, this is one of the perpetual or inexhaustible resources you told me about, not a renewable one.
54:47No matter how much we use the perpetual resources, they'll always be around.
54:53D. Oil.
54:55No, that's a fossil fuel.
54:57All fossil fuels are non-renewable resources.
55:00So the only renewable resource here is the tree.
55:05That makes the answer A.
55:1014. Watering plants and grass in the early morning is one way to conserve water.
55:16Why?
55:18A. Plants only absorb water in the morning.
55:22No, plants can absorb water any time of day.
55:26Take a look at the next one.
55:28Okay, Marco.
55:30B. Less water evaporates into the air in the cool morning.
55:34C. Less water evaporates into the air in the cool morning.
55:38This leaves more water for plants to absorb and allows shorter watering times.
55:43That's true.
55:45C. Water used in the morning can be recycled in the evening.
55:50That doesn't make sense.
55:52If some sort of system is in place to catch unused water to be recycled,
55:57it can be used any time, not just in the morning.
56:01D. Water is more pure in the morning.
56:05This one doesn't make sense either.
56:07I guess that means you're sticking with answer B then.
56:10Yup.
56:17And now for the last question.
56:2115. Which of the following is not a way to help conserve energy?
56:27A. Plant trees in the landscaping around buildings.
56:31The trees would provide shade from the sun and help to block wind,
56:35which would help with cooling and heating bills.
56:39But the question is asking which one is not a way to conserve energy.
56:44How about B. Turn off machines when they are not being used.
56:49That's definitely a way to conserve energy.
56:53Check the next one.
56:54Sure thing, Marco.
56:56C. Both A and B.
56:59No, those are both good ways to conserve energy.
57:02So that means our answer must be D.
57:05Take lots of bubble baths.
57:13Wow! You did a great job on this practice earth science test.
57:20I agree. Nice work.
57:22Hey, science fans, you can download this earth science test at my website.
57:27Just visit www.marcothepencil.com.
57:33Ciao!
57:52www.marcothepencil.com