Working with the model

Read the following extended definition.

To describe what a volcano is not is much easier than to give a concise definition of what it is. A volcano is a vent or chimney, which connects a reservoir of molten matter, known as magma, in the depths of the crust of the earth with the surface of the earth. The material ejected through the vent frequently accumulates around the opening, building up a cone called the volcanic edifice. The loftiest mountains on earth are volcanic edifices. The material ejected consists of liquid lava and broken fragments of partially or completely solidified rock as well as great quantities of gases. The gases are the motivating force and the most important factor in volcanic action. Some authors have maintained that the only feature common to all volcanoes is the channel through which the molten or gaseous material reaches the surface, and therefore a volcano should be defined as “the vent through which this material is erupted”. This, however, leaves us in the difficult position of trying to explain that Vesuvius is not really a volcano but merely a mountain built around one! As now used, the term volcano includes both the vent and the accumulation (cone) around it.

Volcanic eruptions vary between two extremes. In one, the lava rises more or less quietly to the surface and overflows the lip of the crater. The gases bubble through the lava and escape undramatically or, in some instances, rush out with sufficient force to form lava fountains hundreds of feet in height. Nevertheless, the lava is not dispersed but flows away as a river. . . . On the other extreme, tremendous explosions occur in the chimney. As the lava rises into zones of less pressure, it "froths" because of admixture with the rapidly expanding gases, and is ejected in the form of ash and pumice (pyroclastics). ... It was this type of eruption that buried Pompeii in the classic eruption of Vesuvius in a.d. 79. ... The essential

difference in the two types is in the gas content and the manner in which the gas is released when the magma reaches the surface. . . . The great majority of the volcanoes of the world are found between the two extremes described, yielding both lava and fragmental products.

Fred M. Bullard Adapted from Volcanoes of the Earth

A. Think about the definition in this essay.

1. What term is defined? Where is the formal definition found? List the three parts of the formal definition.

2. What is the author's purpose in the first sentence? How does it direct the attention of the reader to the formal

definition?

3. What additional information is given in the first paragraph? What information is given in the second

paragraph?

4. Which of the methods mentioned earlier in this lesson did the author use to develop his extended definition?

Show where the author used each one.

5. What main idea did the author leave with you? What information did you gain from this essay?

B. Imagine that you are writing extended definitions similar to the model. Complete each of the statements begun below by using one of these methods of development: comparison or contrast, synonym, narrative, or metaphor.

Jeans are .... Clogs are ....

A sports car is .... A totem pole is ....

Football is .... Solar heating is ....

C. Imagine that you are preparing to write an extended definition of the Atlantic salmon. Read the formal definition and the details below.

‘The Atlantic salmon is an anadromous fish that lives most of its life in the ocean but returns to the same stream in which it was spawned.’

The details are:

• became extinct in Connecticut

• disappearing in Maine

• not overfished

• can jump as high as twelve feet out of the water

• average ten pounds, some reach forty to seventy pounds

• victim of obstacles constructed by people

• 103 seen out of 600,000 released in 1970

1. In what order would you organize these details in your extended definition?

2. Select two of the details and expand each of them by using a different method of development, such as comparison or contrast, synonym, narrative, or metaphor.