Skip to the content
Peabody TeachFor teachers and grown-ups

The Chilly Layer Beneath the Warm Sea

6th grade nonfiction passage about temperature layers in the ocean: 238 words, six questions, an answer key and vocabulary.

6th grade nonfiction temperature layers in the ocean 238 words

The Chilly Layer Beneath the Warm Sea

If you dive down from the surface of the sea on a sunny day, the first few feet feel warm. Go a little deeper, and you may cross an invisible line where the water suddenly turns chilly. That line has a name. It is the thermocline, the layer where the temperature drops quickly as the depth increases.

The ocean has three main parts. At the top is a surface layer. The sun warms it, and the wind and waves churn it, so its temperature is fairly even. Below the thermocline lies the deep water, which is cold and dark. The sunlight barely reaches it, so it stays cold all year long. The thermocline sits between them like a thin blanket.

The thermocline matters because warm water is lighter than cold water. A layer of light water resting on heavy water is steady, so the two do not mix easily. That means the chilly layer works a bit like a lid. Nutrients that sink toward the bottom, such as the remains of dead plankton, often stay down there instead of rising to the sunlit surface.

Where the sea is warmest, near the equator, the thermocline is usually always present. In colder regions, it may appear in summer and fade away in winter, when storms stir the water from top to bottom. Scientists track it because it affects where fish gather and how the ocean moves heat around the planet.

Questions

  1. What is the thermocline? in the text

  2. Why is the temperature of the surface layer fairly even? in the text

  3. Why does the deep water stay cold all year? in the text

  4. Why do the warm and cold layers not mix easily? in the text

  5. How is the thermocline like a lid? think about it

  6. Why might a thermocline fade away in winter in cold regions? think about it

Words to know

thermocline
the layer where ocean temperature drops quickly
churn
to stir up and mix with force
plankton
tiny living things that drift in the sea
equator
the imaginary line around the middle of Earth
nutrients
substances that living things need to grow
Share

One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 230 words · Flesch-Kincaid grade 4.5

Dive down from the top of the sea on a sunny day. The first few feet feel warm. Go a little deeper, and you may cross an invisible line where the water turns chilly. That line has a name. It is the thermocline. It is the layer where the water gets colder fast as you go deeper.

The ocean has three main parts. At the top is a surface layer. The sun warms it, and wind and waves churn it, so its temperature is fairly even. Below the thermocline is the deep water. It is cold and dark. Sunlight barely reaches it, so it stays cold all year. The thermocline sits between them like a thin blanket.

The thermocline matters because warm water is lighter than cold water. Light water resting on heavy water is steady, so the two do not mix easily. The chilly layer works a bit like a lid. Nutrients that sink toward the bottom, such as the remains of dead plankton, often stay down there. They do not rise to the sunny surface.

Where the sea is warmest, near the equator, the thermocline is usually always there. In colder places, it may appear in summer and fade in winter, when storms stir the water from top to bottom. Scientists track it because it affects where fish gather and how the ocean moves heat around the planet.

▲ This passage · 238 words · Flesch-Kincaid grade 6.1

If you dive down from the surface of the sea on a sunny day, the first few feet feel warm. Go a little deeper, and you may cross an invisible line where the water suddenly turns chilly. That line has a name. It is the thermocline, the layer where the temperature drops quickly as the depth increases.

The ocean has three main parts. At the top is a surface layer. The sun warms it, and the wind and waves churn it, so its temperature is fairly even. Below the thermocline lies the deep water, which is cold and dark. The sunlight barely reaches it, so it stays cold all year long. The thermocline sits between them like a thin blanket.

The thermocline matters because warm water is lighter than cold water. A layer of light water resting on heavy water is steady, so the two do not mix easily. That means the chilly layer works a bit like a lid. Nutrients that sink toward the bottom, such as the remains of dead plankton, often stay down there instead of rising to the sunlit surface.

Where the sea is warmest, near the equator, the thermocline is usually always present. In colder regions, it may appear in summer and fade away in winter, when storms stir the water from top to bottom. Scientists track it because it affects where fish gather and how the ocean moves heat around the planet.

■ Harder · 251 words · Flesch-Kincaid grade 7.5

If you were to dive down from the surface of the sea on a sunny day, the first few feet would feel pleasantly warm. Go a little deeper, however, and you may cross an invisible boundary where the water abruptly turns chilly. That boundary has a name. It is the thermocline, the layer in which the temperature drops rapidly as the depth increases.

The ocean has three main parts. At the top lies a surface layer, which the sun warms and the wind and waves churn, so its temperature is fairly uniform. Beneath the thermocline lies the deep water, which is cold and dark. Sunlight barely penetrates that far, so the deep water remains cold throughout the year. The thermocline lies between the two, like a thin blanket.

The thermocline is significant because warm water is lighter than cold water. A layer of light water resting on heavy water is stable, so the two do not mix easily. As a result, the chilly layer behaves somewhat like a lid. Nutrients that sink toward the bottom, such as the remains of dead plankton, frequently stay down there instead of rising to the sunlit surface.

Where the sea is warmest, near the equator, a thermocline is usually present all year. In colder regions it may appear in summer and then fade away in winter, when storms stir the water from top to bottom. Scientists keep track of it because it influences where fish gather and how the ocean moves heat around the planet.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put thermocline, churn, plankton, equator and nutrients on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 2 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 5 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "The Chilly Layer Beneath the Warm Sea"?

It was written for 6th grade. It has 238 words and works out to a Flesch-Kincaid grade level of about 6.1. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are six. 4 ask for something the text says directly and 2 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 2 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

Nothing you do here is sent to us. No sign-in, no ads.