Earth, Space, and Planetary Systems

Topography and Landform Classification

Our Earth has many different shapes on its surface. Some places are high. Some places are low. Some places are flat. Some places are surrounded by water.

When we look at the shape of the land, we are learning about topography. Topography means how the land looks and feels. We can talk about land that is tall, low, flat, or bumpy.

We can also group land into kinds. These kinds are called landforms. A landform is a shape of land you can see on Earth.

In this lesson, we will learn about 5 important landforms:

• mountains
• valleys
• plains
• plateaus
• islands

1. Mountains

A mountain is very high land. It rises up taller than the land around it. Mountains often have steep sides and a top called a peak.

If you stand far away and see land that goes up high like a giant bump or point, you may be looking at a mountain.

• Mountains are high.
• Mountains are usually not flat on top.
• Mountains stand above nearby land.

2. Valleys

A valley is low land between higher lands, like hills or mountains. A valley can look like a long dip in the land.

Some valleys have rivers running through them. If mountains are on both sides and the land in the middle is lower, that lower place is a valley.

• Valleys are low.
• Valleys are often between higher places.
• Valleys can be long and wide or small and narrow.

3. Plains

A plain is a large area of land that is mostly flat. Plains do not rise up high like mountains.

When you look across a plain, the land may seem smooth and open. Plains are good examples of land that is flat or almost flat.

• Plains are flat.
• Plains are often wide and open.
• Plains are not tall like mountains.

4. Plateaus

A plateau is land that is high up, but the top is flat. It is like a table-shaped piece of land.

This makes a plateau different from a mountain. A mountain is high and pointed or steep. A plateau is high but flatter on top.

• Plateaus are high.
• Plateaus have a flat top.
• Plateaus rise above nearby land.

5. Islands

An island is land that is surrounded by water. Water is all around it.

An island can be high like a mountain island or flat like a small sandy island. What makes it an island is not its height. What makes it an island is that water is around it.

• Islands are surrounded by water.
• Islands can be big or small.
• Islands can be high or flat.

How to Classify Landforms

To classify means to sort into groups. We classify landforms by looking at their shape and where they are.

Here are good questions to ask:

• Is the land high or low?
• Is the land flat or pointed?
• Is the land between higher land?
• Is the land surrounded by water?

These clues help us choose the correct landform name.

Let’s Compare the Landforms

• Mountain: high land with steep sides, often with a peak
• Valley: low land between higher lands
• Plain: wide, flat land
• Plateau: high land with a flat top
• Island: land surrounded by water

Worked Example 1

You see a piece of land that is very tall. It rises high above the land around it. The top is not flat.

Question: Is it a mountain, valley, or plain?

Think: It is high. It is not flat. It stands above nearby land.

Answer: It is a mountain.

Worked Example 2

You see land that is low in the middle. There are higher mountains on both sides.

Question: Is it a valley or a plateau?

Think: A valley is low land between higher land. A plateau is high land with a flat top.

Answer: It is a valley.

Worked Example 3

You see a large area of land. It is flat for a long distance. It does not rise high.

Question: Is it a plain or a mountain?

Think: Plains are flat and wide. Mountains are high.

Answer: It is a plain.

Worked Example 4

You see land that is higher than the land nearby. The top is flat like a table.

Question: Is it a plateau or a mountain?

Think: Both can be high. But a plateau has a flat top.

Answer: It is a plateau.

Extra Practice Thinking

1. If water is all around a piece of land, what is it?

   Answer: an island

2. If land is low and sits between two hills, what is it?

   Answer: a valley

3. If land is high and flat on top, what is it?

   Answer: a plateau

4. If land is wide and flat, what is it?

   Answer: a plain

Why This Matters

Learning landforms helps us describe Earth. It helps us talk about where places are and what they look like. It also helps us notice how one place can be different from another place.

When you look at land, you can be a land detective. Look for clues about height, shape, and water. Then you can classify the landform.

Summary

Topography is the shape of Earth’s surface. Landforms are different kinds of land shapes.

A mountain is high land. A valley is low land between higher lands. A plain is wide and flat. A plateau is high with a flat top. An island is land surrounded by water.

If you remember to look for high, low, flat, and water all around, you can classify many landforms correctly.

Hydrological Distribution means where water is found on Earth.

Earth has water in many places. Some water is in big oceans. Some water is in rivers, lakes, ponds, and glaciers.

Water is very important. People, plants, and animals all need water to live.

Let’s learn about the different places water can be found and how they are alike and different.

1. Oceans

Oceans are the biggest bodies of water on Earth. Ocean water is saltwater.

Saltwater is water that tastes salty. People do not drink ocean water.

Oceans are huge and deep. They cover much of Earth.

2. Rivers

Rivers are water that moves from one place to another. A river flows across the land.

Most rivers are freshwater. Freshwater is water that is not salty.

Rivers can be long or short. They can move fast or slow.

3. Lakes

Lakes are bodies of water with land around them. Most lakes are freshwater.

A lake does not move like a river. The water mostly stays in one place.

4. Ponds

Ponds are like small lakes. They are usually smaller and shallower than lakes.

Most ponds are freshwater.

You may see fish, frogs, ducks, and plants in a pond.

5. Glaciers

Glaciers are big, slow-moving ice. A glacier is made of frozen freshwater.

Even though a glacier is ice, it is still water.

Glaciers are found in very cold places.

Saltwater and Freshwater

There are two important kinds of water we are learning about:

• Saltwater — found in oceans
• Freshwater — found in most rivers, lakes, ponds, and glaciers

A simple way to remember:

• Ocean = saltwater
• River, lake, pond, glacier = freshwater

How water bodies are different

• Ocean: very big, salty
• River: moving freshwater
• Lake: still freshwater with land around it
• Pond: small, still freshwater
• Glacier: frozen freshwater

How water bodies are alike

• They all have water.
• They are all part of Earth.
• Plants and animals can live in or near them.
• They help people and nature.

Worked Example 1

Question: Mia sees a very big body of water. The water is salty. Is it most likely an ocean or a lake?

Think: Oceans are big and salty. Most lakes are freshwater.

Answer: It is most likely an ocean.

Worked Example 2

Question: Ben sees water moving across the land. Is he looking at a river or a pond?

Think: Rivers move. Ponds usually stay still.

Answer: He is looking at a river.

Worked Example 3

Question: Ava sees a large block of ice in a very cold place. Is it a glacier or an ocean?

Think: A glacier is frozen freshwater. An ocean is salty liquid water.

Answer: It is a glacier.

Worked Example 4

Question: Which of these are usually freshwater: river, ocean, pond?

Think: Oceans are saltwater. Rivers and ponds are usually freshwater.

Answer: River and pond are usually freshwater.

Let’s remember with a list

1. Oceans are saltwater.
2. Rivers are moving freshwater.
3. Lakes are still freshwater.
4. Ponds are small, still freshwater.
5. Glaciers are frozen freshwater.

Quick check

• Which water body is salty? Ocean
• Which water body moves? River
• Which water body is small and still? Pond
• Which water body is frozen? Glacier

Summary

Water is found in many places on Earth. Oceans are saltwater. Most rivers, lakes, ponds, and glaciers are freshwater.

When we learn hydrological distribution, we are learning where Earth’s water is and what kind of water it is.

Soil Composition and Strata

Have you ever dug in the ground and seen dirt that looked different as you went deeper? That is because soil is made of different parts, and it can form in layers.

Soil is very important. Plants grow in soil. Many small animals live in soil. Soil helps hold water and air that living things need.

Let’s learn what soil is made of and how soil can have layers called strata.

What is soil made of?

Soil is not just one thing. Soil is a mixture, which means different things are mixed together.

• Small pieces of rock like sand, silt, and clay
• Water
• Air
• Humus, which is old dead plant and animal material that has broken down into tiny bits

All of these parts work together to help plants live and grow.

Small pieces of rock

Some of soil comes from rock that has broken into tiny pieces.

• Sand has bigger grains that feel rough.
• Silt has smaller grains and feels soft.
• Clay has very tiny pieces and can feel sticky when wet.

These rock pieces mix together to make different kinds of soil.

Water in soil

Soil can hold water. Plants use this water to grow. After rain, water moves into the soil and fills some of the tiny spaces.

Air in soil

Soil also has tiny spaces with air in them. Plant roots and small living things in the soil need air.

Humus in soil

Humus is made from old leaves, dead plants, and other living things that have broken down. Humus is dark and rich. It helps soil stay healthy for plants.

Why is soil important for plants?

Plants need soil for many reasons.

• Soil holds the plant in place.
• Soil gives the plant water.
• Soil gives the plant air around its roots.
• Soil with humus helps plants grow well.

If soil has the right mix of rock pieces, water, air, and humus, plants can grow better.

What are strata?

Strata means layers. When you dig down into the ground, you may see one layer on top and another layer below it.

One layer may be darker because it has more humus. Another layer may be lighter because it has more sand or clay.

Soil layers can look different in:

• Color
• Texture, or how it feels
• What it is made of

A simple way to think about soil layers

The top layer of soil often has more humus. That is where many plants grow best.

Below that, the soil may have less humus and more small rock pieces.

Even deeper down, you may find bigger pieces of rock.

We can think of it like this:

1. Top layer: darker soil with more humus
2. Middle layer: lighter soil with more sand, silt, or clay
3. Bottom layer: rock or bigger broken rock pieces

Not every place looks exactly the same, but many places have layers like these.

How soil forms

Over a long time, rocks break into smaller pieces. Leaves and plants also break down and become humus. Water and air mix into the ground too.

Little by little, soil forms. Then the soil can build up in layers.

Worked Example 1

A child says, “Soil is only dirt and nothing else.” Is that correct?

Step 1: Think about what soil is made of.

• Small rock pieces
• Water
• Air
• Humus

Step 2: Decide if soil is only one thing.

No. Soil is not only dirt. Soil is a mixture of many things.

Answer: The child is not correct. Soil is made of rock pieces, water, air, and humus.

Worked Example 2

You touch two kinds of soil. One feels rough. One feels sticky when wet. What might they be?

Step 1: Match the feeling to the soil part.

• Rough feeling: sand
• Sticky when wet: clay

Answer: The rough soil might have more sand. The sticky wet soil might have more clay.

Worked Example 3

You dig a hole. The top soil is dark. The soil under it is lighter. Why might the top soil be darker?

Step 1: Remember what makes soil dark and rich.

Humus is dark. It comes from old plants and living things that have broken down.

Step 2: Think about the top layer.

The top layer often has more humus.

Answer: The top soil may be darker because it has more humus.

Worked Example 4

A plant is growing in soil. What are two things in the soil that help the plant?

Step 1: Name parts of soil that help plants.

• Water
• Air
• Humus
• Small rock pieces that help make the soil

Step 2: Choose two.

One good answer is water and humus.

Answer: The soil helps the plant by giving it water and by having humus. Air in the soil helps too.

Let’s remember the big ideas

• Soil is a mixture.
• Soil is made of sand, silt, clay, water, air, and humus.
• Humus is broken-down old plant and animal material.
• Soil helps plants by holding water and air and giving roots a place to grow.
• Soil can have strata, or layers.
• The top layer often has more humus, and deeper layers often have more rock pieces.

Brief Summary

Soil is made of many parts mixed together. It has tiny rock pieces, water, air, and humus. Soil can form layers called strata, and these layers can look and feel different. Healthy soil helps plants live and grow.

Earth's Rotation and the Day/Night Cycle

Have you ever wondered why it is bright in the morning and dark at night? It happens because Earth is always turning.

Earth is the planet where we live. It spins around and around, like a top. This turning is called rotation.

Earth turns very slowly. One full turn takes 24 hours. That is one whole day.

As Earth turns, different parts of Earth face the Sun. The side facing the Sun has daytime. The side turned away from the Sun has nighttime.

So, day and night happen because Earth rotates. The Sun does not go off. Earth turns, and that makes it seem like the Sun moves across the sky.

Main Ideas

• Earth rotates, or spins.
• Earth rotates on an axis. You can think of the axis as an imaginary line through Earth.
• One full rotation takes 24 hours.
• The side of Earth facing the Sun has day.
• The side of Earth facing away from the Sun has night.

What Is Rotation?

Rotation means turning in a circle. If you spin around one time, you made one full turn. Earth does this too, but much more slowly.

Earth keeps turning all the time. We do not feel it because Earth is very big, and we move with it.

What Is the Axis?

Earth spins on its axis. The axis is not something you can see. It is an imaginary line that goes through the middle of Earth from top to bottom.

Earth turns around this line, just like a basketball can spin around a line through its center.

How Day Happens

When your part of Earth is facing the Sun, sunlight shines on it. The sky looks bright. It is daytime.

During the day, you may see the Sun in the sky. The Sun looks like it moves, but really Earth is turning.

How Night Happens

When your part of Earth turns away from the Sun, it does not get sunlight. The sky gets dark. It is nighttime.

At night, you may see the Moon and stars. This happens because your side of Earth is turned away from the Sun.

One Full Day

Earth makes one full spin in 24 hours.

We can show that like this:

One full day = \(24\) hours

That means:

• morning is part of the day,
• afternoon is part of the day,
• evening is when day changes to night,
• night is the dark time before morning comes again.

After Earth keeps turning, morning comes back again.

Think About a Ball and a Flashlight

You can imagine Earth as a ball and the Sun as a flashlight.

• The flashlight shines on one side of the ball.
• That bright side is day.
• The dark side is night.
• If you slowly turn the ball, different parts become bright and dark.

That is like Earth rotating and making day and night.

Worked Examples

Example 1: Which side has day?

A ball is lit by a flashlight. One side is bright. One side is dark. Which side has day?

Answer: The bright side has day because it is facing the light, like Earth facing the Sun.

Example 2: What makes night?

A child says, “Night happens because the Sun goes away.” Is that right?

Answer: Not quite. Night happens because Earth turns. When our part of Earth turns away from the Sun, it becomes dark.

Example 3: How long is one full turn?

Earth spins around one whole time. How long does that take?

Answer: It takes 24 hours.

We can write it like this:

$$1 \text{ full rotation} = 24 \text{ hours}$$

Example 4: What happens next?

It is daytime where you are. Earth keeps rotating. Later, your part of Earth turns away from the Sun. What happens next?

Answer: It becomes nighttime because your part of Earth is no longer facing the Sun.

Easy Clues to Remember

• Facing the Sun = day
• Facing away from the Sun = night
• Earth spins = rotation
• 1 full spin = 24 hours

Let’s Review

1. Earth is always spinning.
2. This spinning is called rotation.
3. Earth spins on its axis.
4. The side facing the Sun has day.
5. The side facing away from the Sun has night.
6. One full spin takes 24 hours.

Brief Summary

Day and night happen because Earth rotates. Earth spins on its axis one full time every 24 hours. When your part of Earth faces the Sun, it is day. When your part of Earth turns away from the Sun, it is night.

Apparent Solar Motion means the Sun looks like it moves across the sky each day.

We see the Sun come up in the east in the morning. Later, it looks high in the sky. Then it looks lower and lower until it sets in the west.

But the Sun is not really going around Earth every day. Earth is turning. Earth spins like a top. As Earth turns, the Sun appears to move across the sky.

This is called apparent solar motion. Apparent means how something looks. So the Sun looks like it is moving, even though Earth is the thing that is turning.

Introduction

Have you ever seen the Sun in the morning and then looked for it again later? In the morning, it is on one side of the sky. In the afternoon, it is in a different place.

This change happens every day in a pattern we can notice. The Sun seems to move from east to west. This pattern is easy to observe, and it helps us know about daytime.

Main Teaching Points

1. The Sun seems to move across the sky.

In the morning, the Sun rises. We call this sunrise. The Sun rises in the east.

In the middle of the day, the Sun looks higher in the sky.

At the end of the day, the Sun goes down. We call this sunset. The Sun sets in the west.

2. This happens in a predictable pattern.

The Sun follows the same kind of path each day:

• Morning: sunrise in the east
• Later: higher in the sky
• Evening: sunset in the west

This pattern repeats again and again.

3. Earth is turning.

Earth spins all the time. This spinning is called rotation.

Because Earth turns, different places on Earth face the Sun at different times. When your part of Earth faces the Sun, it is daytime. When your part turns away from the Sun, it is nighttime.

4. The Sun only looks like it is moving.

If you are in a car, trees outside may look like they are moving past you. But really, the car is moving.

The Sun is like that for us. It looks like the Sun is moving, but really Earth is turning.

5. We can use shadows to notice the Sun's apparent motion.

As the Sun appears to move, shadows change too.

• In the morning, shadows may point one way.
• Later, shadows get shorter.
• In the evening, shadows get longer again and point another way.

Changing shadows help show that the Sun appears to move across the sky.

Examples

Example 1: Morning and evening

Lena sees the Sun when she eats breakfast. It is low in the sky. Later, at dinner time, she sees the Sun low again on the other side of the sky.

What is happening?

The Sun appears to move across the sky during the day. In the morning it is in the east. In the evening it is in the west.

Example 2: What is really moving?

Jamal says, “The Sun goes around Earth every day.”

Is that right?

Not for this daily pattern. The Sun only looks like it moves across the sky. Earth is turning, and that makes the Sun seem to move.

Example 3: Using a shadow

Mia puts a stick in the ground. She looks at its shadow in the morning, at noon, and in the evening.

What might she notice?

• The shadow changes place.
• The shadow gets shorter and then longer.

This happens because the Sun appears to move across the sky as Earth turns.

Example 4: Putting the pattern in order

Put these in order:

1. Sun is higher in the sky
2. Sunset in the west
3. Sunrise in the east

Answer:

1. Sunrise in the east
2. Sun is higher in the sky
3. Sunset in the west

This is the daily pattern of apparent solar motion.

Try to Remember

• The Sun looks like it moves across the sky.
• The Sun seems to rise in the east.
• The Sun seems to set in the west.
• Earth is turning, and that makes the Sun appear to move.
• Shadows change during the day because the Sun appears to move.

Brief Summary

Every day, the Sun seems to move across the sky from east to west. This is called apparent solar motion.

The Sun is not really moving around Earth each day. Earth is turning, and that makes the Sun look like it is moving. We can notice this pattern by watching the Sun and by seeing shadows change.

Lunar Phases and Orbit

Look up at the sky at night. Sometimes the Moon looks big and round. Sometimes it looks like a tiny curved shape. Why does the Moon change how it looks?

The Moon does not make its own light. The Moon looks bright because sunlight shines on it. We see the part of the Moon that the Sun lights up.

The Moon also moves around Earth. This path around Earth is called an orbit.

As the Moon goes around Earth, we see different amounts of its bright part. That is why the Moon seems to change shape. These changes are called lunar phases.

Important idea: The Moon is always shaped like a ball. It is not really changing shape. We just see different parts of the bright side.

Main Teaching Points

• The Sun gives light.
• The Moon reflects, or bounces, the Sun's light.
• The Moon orbits Earth.
• As the Moon moves, the bright part we see looks different.
• These different looks are called phases.

Think about a flashlight and a ball. If you shine a flashlight on a ball, only part of the ball is bright. If you walk around the ball, the bright part looks different from different places. The Moon, Earth, and Sun work in a similar way.

The Moon's orbit means the Moon travels around Earth again and again. It keeps going in a loop.

We can think of the Moon's trip around Earth like this:

Moon goes around Earth in one loop.

Sometimes we see a little bright part. Sometimes we see half. Sometimes we see all of the bright side.

Common Moon Phases

1. New Moon - We cannot really see the bright part from Earth.
2. Crescent Moon - We see a small curved bright part.
3. Half Moon - We see half of the Moon bright.
4. Gibbous Moon - We see more than half bright.
5. Full Moon - We see the whole bright side facing Earth.

Then the Moon keeps moving, and the phases happen again.

What causes the phases?

The phases happen because:

• the Sun shines on the Moon, and
• the Moon moves around Earth.

When the Moon is in a new place in its orbit, we see a new amount of the bright side.

What phases do NOT mean

• The Moon is not being cut into pieces.
• The Moon is not changing into different shapes.
• Clouds do not cause the Moon phases.

Clouds can hide the Moon, but they do not make the phases. The phases happen because of sunlight and the Moon's orbit.

Worked Examples

Example 1: You see a round, bright Moon in the sky. What phase is it?

Answer: It is a full moon.

Why? A full moon is when we see the whole bright side of the Moon.

Example 2: You see only a small curved bright part of the Moon. What phase might it be?

Answer: It is a crescent moon.

Why? A crescent moon looks like a small curve or a banana shape.

Example 3: A child says, "The Moon makes its own light." Is that correct?

Answer: No, that is not correct.

Why? The Sun gives the light. The Moon reflects the Sun's light.

Example 4: A child says, "The Moon changes shape each night." Is that correct?

Answer: No. The Moon stays round like a ball.

Why? We only see different amounts of the bright side as the Moon orbits Earth.

Let's Remember

• The Moon orbits Earth.
• The Sun lights the Moon.
• We see different amounts of the Moon's bright side.
• These different looks are called lunar phases.

Quick Check

1. Does the Moon make its own light?
2. What do we call the Moon moving around Earth?
3. What is the name for the Moon's changing looks?
4. What phase is the Moon when it looks round and full?

Answers

1. No.
2. An orbit.
3. Lunar phases.
4. Full moon.

Summary

The Moon moves around Earth in an orbit. The Sun shines on the Moon. As the Moon moves, we see different amounts of its bright side. That is why we see phases like new moon, crescent, half moon, and full moon.

Stellar Observation and Constellations

Have you ever looked up at the night sky and seen tiny shining dots? Those dots are called stars. Stars are far away in space, and they give off their own light.

One special star is the Sun. The Sun is the star that is closest to Earth. It looks much bigger and brighter than the other stars because it is much closer to us.

In the daytime, we usually cannot see the other stars. That is because the Sun is so bright. Its light makes the sky look bright blue, so the other stars are hidden from our eyes.

At night, when our part of Earth faces away from the Sun, the sky gets dark. Then we can see many stars. Some stars seem to make shapes or pictures in the sky. These star pictures are called constellations.

People long ago looked at groups of stars and imagined shapes, like animals or people. They gave these star groups names. Today, we still use some of those names to talk about constellations.

Main Ideas

• Stars shine: Stars make their own light.
• The Sun is a star: It is our closest star.
• The Sun is very bright: In daytime, its light hides the other stars.
• Constellations are patterns: Some stars seem to make shapes in the night sky.
• Patterns can be found again: The same constellation shapes can be seen again and again.

What does it mean to observe stars?

To observe means to look carefully. When we observe stars, we look at the night sky and notice what we see.

We can notice:

• how many stars we can see,
• which stars look bright,
• where the stars are in the sky,
• and whether some stars make a pattern.

When we look carefully, we may see that some stars seem close together. Our eyes connect them into shapes. That is how we notice constellations.

Why can we see stars at night but not in the day?

Earth spins. During the day, our side of Earth faces the Sun. The Sun lights up the sky.

At night, our side of Earth faces away from the Sun. The sky becomes dark, and then many stars can be seen.

You can think of it like this:

• Day: Sun is shining brightly, so other stars are hard to see.
• Night: Sky is darker, so stars are easier to see.

What are constellations?

Constellations are groups of stars that make a pattern in the sky. The stars are not really connected by lines. But people imagine lines between them to make a picture.

For example, a few stars might look like a scoop, a kite, or an animal shape. Different people may imagine different pictures, but some constellation names have been used for a very long time.

Constellations help people talk about where stars are in the sky. If someone says a certain constellation name, other people know which star pattern to look for.

Important things to remember

1. The Sun is a star.
2. Stars give off light.
3. We see many more stars at night than in the daytime.
4. Constellations are star patterns.
5. The same patterns can be seen again on clear nights.

Worked Example 1

Question: Maya looks up in the sky at noon. She sees the Sun, but she does not see other stars. Why?

Answer: The Sun is very bright. In the daytime, its light makes the sky bright, so the other stars are hidden from Maya's eyes.

Worked Example 2

Question: Leo looks at the sky on a dark, clear night. He sees many tiny lights. What are they?

Answer: They are stars. At night, the sky is dark enough for Leo to see them.

Worked Example 3

Question: Ana sees a group of stars that looks like a shape. What is this called?

Answer: It is called a constellation. A constellation is a pattern of stars in the sky.

Worked Example 4

Question: Which sentence is true?

• A. The Sun is not a star.
• B. The Sun is a star.

Answer: B. The Sun is a star. It is the closest star to Earth.

Try thinking about these ideas

• If the sky is bright, are stars easy or hard to see?
• If the sky is dark, can you see more stars?
• If stars seem to make a shape, what is that shape called?

Safety note

Never look straight at the Sun. It is too bright and can hurt your eyes. It is safer to observe stars at night.

Summary

Stars are bright objects in space that make their own light. The Sun is also a star, and it is the closest star to Earth. In the daytime, the Sun's bright light hides the other stars. At night, we can see many stars, and some of them seem to make patterns called constellations.