Anatomy of a Volcano

Volcanic activity begins when a fissure (crack) develops in the crust as magma moves forcefully toward the surface. As the gas-rich magma moves up through a fissure, its path is usually localized into a circular conduit, or pipe, that terminates at a surface opening called a vent. Successive eruptions of lava, pyroclastic material, or a combination of both, often separated by long periods of inactivity, eventually build the cone-shaped structure we call a volcano.

Located at the summit of most volcanoes is a somewhat funnel-shaped depression, called a crater (crater = a bowl). Volcanoes that are built primarily of pyroclastic materials typically have craters that form by gradual accumulation of volcanic debris on the surrounding rim. Other craters form during explosive eruptions as the rapidly ejected particles erode the crater walls. Craters also form when the summit area of a volcano collapses following an eruption. Some volcanoes have very large circular depressions called calderas that have diameters greater than 1 km and in rare cases can exceed 50 km.

During early stages of growth most volcanic discharges come from a central summit vent. As a volcano matures, material also tends to be emitted from fissures that develop along the flanks or at the base of the volcano. Continued activity from a flank eruption may produce a small parasitic cone. Italy’s Mount Etna, for example, has more than 200 secondary vents, some of which have built parasitic cones. Many of these vents, however, emit only gases and are appropriately called fumaroles (fumus = smoke).

Task 3. Answer the following questions, using the vocabulary from Task 1.

1. When does volcanic activity usually begin?

2. What is vent?

3. What is a volcano?

4. What is a crater?

5. How do craters form?

6. What are calderas?

7. Where do parasitic cones form?

8. What is a fumarole?

Task 4. Look at Figure 7.1 and try to describe the anatomy of a volcano.

Task 5. Find English equivalents for the following (see the text). Try to build up your own sentences with them.

Початок вулканічної діяльності; збагачена газом магма; рухатись вверх через розлом; завершитись отвором на поверхні; послідовні виверження лави; довгі періоди бездіяльності; конічна структура; воронкоподібна западина; поступове накопичення вулканічних уламків; частинки, які швидко вивергаються; ранні стадії формування вулкану; тріщини, які утворюються з боків вулкану; побічні (другорядні) вихідні отвори.

Task 6. Give a short summary of the text from Task 2.

Grammar focus The Present Indefinite versus the Future Indefinite tenses in complex sentences

Task 1. Read the following sentences, translate them into Ukrainian. Pay attention to the forms of the verbs in the Present and the Future Indefinite tenses.

1. If this activity is sustained, it will eventually build a chain of volcanic structures that emerge from the sea as a volcanic island arc.

2. If spreading continues in this region, the African plate will split into two plates, separated by a new ocean basin.

3. As long as temperatures within the interior of our planet remain significantly higher than those at the surface, material within Earth will continue to circulate.

4. When a mineral exhibits cleavage, it will break into pieces that all have the same geometry.

5. If demand for a metal increases and prices rise sufficiently, the status of a previously unprofitable deposit will change.

6. When enough mantle-derived basaltic magma is formed, it will buoyantly rise toward the surface.

7. When magma rises (or the rocks confining the magma fail) a reduction in pressure will occur and the dissolved gases will begin to separate from the melt, forming tiny bubbles.

8. When fluid basaltic magmas erupt, the pressurized gases will escape with relative ease.

9. When magma in the uppermost portion of the magma chamber is forcefully ejected by the escaping gases, the confining pressure on the molten rock directly below will drop suddenly.

10. As the conduit enlarges, magma will move upward to produce surface activity.

Task 2. Name the cases when the rule of observing the Present Indefinite and the Future Indefinite tenses in conditional clauses does not work. Provide your own examples.