Revision Volcanoes

Section: Volcanic Eruptions

Circle the letter of the best answer for each question.

   1.  What is the name of the molten rock inside a volcano?

        a. pressure

        b. ash

        c. magma

        d. lava

   2.  What is magma that flows onto the Earth’s surface called?

        a. lava

        b. magma

        c. ash

        d. rock

   3.  What are the areas on top of the Earth where magma and volcanic gases come out?

        a. air holes

        b. meteor craters

        c. geysers

        d. volcanoes

Nonexplosive Eruptions

   4.  Which of the following can happen during nonexplosive eruptions?

        a. violent explosions

        b. tons of rock blasted into the air

        c. huge lava flows

        d. fire shooting into the air

Directed Reading B continued

Explosive Eruptions

Circle the letter of the best answer for each question.

   5.  Which of the following can happen during an explosive volcanic eruption?

        a. calm lava flows

        b. hot debris, ash, and gas shooting into the air

        c. a rainbow

        d. lava fountains

   6.  What is ash?

        a. flowing lava

        b. tiny, dust-sized bits of rock

        c. big chunks of rock

        d. a gas

What Is Inside a Volcano?

   7.  what is a vent?

        a. a magma chamber

        b. an eruption

        c. a crack in the Earth’s crust

        d. an underground volcano

   8.  Where is a volcano’s magma chamber?

        a. at the top of the vent

        b. deep underground

        c. on the volcano’s slope

        d. outside the volcano

Directed Reading B continued

What Makes Up Magma?

Circle the letter of the best answer for each question.

   9.  What affects how explosive a volcanic eruption is?

        a. heat

        b. amount of lava

        c. composition of magma

        d. ash

Water and Magma Are an Explosive Combination

10.  What is most likely to happen if the water content of magma ishigh?

        a. A nonexplosive eruption will occur.

        b. No eruption will occur.

        c. Pressure will decrease.

        d. An explosive eruption is likely.

Silica-Rich Magma Traps Explosive Gases

11.   Which of the following statements is true?

        a. Silica-rich magma has a thin, runny consistency.

        b. Silica-rich magma allows gases to escape easily.

        c. Silica-rich magma causes explosive eruptions.

        d. Silica-rich magma causes nonexplosive eruptions.

What Erupts from a Volcano?

12.What is lava?

        a. liquid magma that flows

        b. magma that blasts into the air and hardens

        c. a mix of gases and water

        d. magma that stays underground

Directed Reading B continued

13.  What is pyroclastic material?

        a. liquid magma that flows

        b. magma that bl asts into the air and hardens

        c. a mix of gases and water

        d. magma that stays underground

Types of Lava

Read the description. Then, draw a line from the dot next to each description to the matching word.

14.  forms underwater in rounded lumps 15.   flows slowly, like dripping wax 16.  has a brittle, jagged crust 17.  cool, stiff lava that forms jumbled heaps	• • • •	a.  aa lava    b.  pillow lava    c.  pahoehoe lava    d.  blocky lava
Types of Pyroclastic Material 18.  large blobs of magma that harden in the air 19.  solid rock blasted out of a volcano 20.  glass-like slivers from exploding gas bubbles 21.  pebblelike bits of magma that cool in the air	• • • •	a.  volcanic blocks    b.  volcanic bombs    c.  lapilli    d.  volcanic ash

Directed Reading B continued

Pyroclastic Flows

Read the words in the box. Read the sentences. Fill in each blank with the word that best completes the sentence.

pyroclastic

temperature

hurricane

22.   A very dangerous type of volcanic flow is a(n) ______________________flow.

23.  Pyroclastic materials can move faster than a(n) ______________________.

24.  The center of a pyroclastic flow has a very high .______________________.