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Obsidian Is Glass Made by a Volcano

4th grade nonfiction passage about volcanic glass: 181 words, six questions, an answer key and vocabulary.

4th grade nonfiction volcanic glass 181 words

Obsidian Is Glass Made by a Volcano

Most rocks are dull and rough, but obsidian is smooth and shiny. It is usually black or very dark, and it looks like glass. In fact, it is a kind of natural glass, and a volcano makes it.

A volcano can send out hot melted rock called lava. As lava cools, the tiny pieces inside it usually have time to lock together into crystals. This gives most rocks a grainy look. Sometimes, though, a thick lava cools very quickly. The pieces do not have time to line up. They freeze in a jumble, and the result is glass.

Obsidian has a special way of breaking. It does not crumble. It snaps into curved pieces with edges that are extremely sharp. Because of that, people long ago used it to make blades and other tools. Some of those tools have been found far from any volcano, which shows that people traded the stone over long distances.

Today, a rock collector can hold a piece of obsidian and feel how smooth it is. It is wise to handle broken pieces with great care.

Questions

  1. What does obsidian look like? in the text

  2. What makes obsidian? in the text

  3. Why does obsidian not have a grainy look like most rocks? in the text

  4. How does obsidian break? in the text

  5. What do tools found far from any volcano suggest? think about it

  6. Why should broken pieces of obsidian be handled with care? think about it

Words to know

obsidian
a smooth, shiny rock that looks like dark glass
lava
hot melted rock that flows out of a volcano
crystals
solid pieces of minerals with flat sides and sharp corners
blades
the sharp cutting parts of tools
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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 · 144 words · Flesch-Kincaid grade 4.3

Most rocks are dull and rough. Obsidian is smooth and shiny. It is usually black. It looks like glass. It is natural glass, and a volcano makes it.

A volcano sends out hot melted rock called lava. As lava cools, tiny pieces inside it usually lock together into crystals. That gives most rocks a grainy look. But sometimes thick lava cools very fast. The pieces have no time to line up. They freeze in a jumble. The result is glass.

Obsidian breaks in a special way. It does not crumble. It snaps into curved pieces with very sharp edges. Long ago, people used it to make blades and tools. Some of these tools were found far from any volcano. So people must have traded the stone over long distances.

Today, a rock collector can feel how smooth obsidian is. Be careful with broken pieces.

▲ This passage · 181 words · Flesch-Kincaid grade 5.2

Most rocks are dull and rough, but obsidian is smooth and shiny. It is usually black or very dark, and it looks like glass. In fact, it is a kind of natural glass, and a volcano makes it.

A volcano can send out hot melted rock called lava. As lava cools, the tiny pieces inside it usually have time to lock together into crystals. This gives most rocks a grainy look. Sometimes, though, a thick lava cools very quickly. The pieces do not have time to line up. They freeze in a jumble, and the result is glass.

Obsidian has a special way of breaking. It does not crumble. It snaps into curved pieces with edges that are extremely sharp. Because of that, people long ago used it to make blades and other tools. Some of those tools have been found far from any volcano, which shows that people traded the stone over long distances.

Today, a rock collector can hold a piece of obsidian and feel how smooth it is. It is wise to handle broken pieces with great care.

■ Harder · 184 words · Flesch-Kincaid grade 7.9

Most rocks are dull and rough, but obsidian is remarkably smooth and glossy. It is typically black or very dark, and it resembles glass. In fact, it is a form of natural glass, and it is produced by a volcano.

A volcano can release hot, melted rock known as lava. As lava cools, the tiny particles inside it usually have enough time to lock together into crystals, which gives most rocks a grainy appearance. Occasionally, however, a thick lava cools extremely quickly. The particles do not have time to arrange themselves in order. They freeze in a jumble, and the result is glass.

Obsidian has a distinctive way of breaking. Instead of crumbling, it snaps into curved pieces with astonishingly sharp edges. For that reason, people long ago used it to make blades and other tools. Some of those tools have been discovered far from any volcano, which shows that people traded the stone across great distances.

Today, a rock collector can hold a piece of obsidian and feel how smooth it is, although it is wise to handle broken pieces with great care.

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 obsidian, lava, crystals and blades 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 "Obsidian Is Glass Made by a Volcano"?

It was written for 4th grade. It has 181 words and works out to a Flesch-Kincaid grade level of about 5.2. 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.

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