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most perfect cones—Mount Mayon in the Philippines and Fujiyama in Japan—exhibit
the classic form of a composite cone, with its steep summit and gently sloping flanks.

Task 3. Find all the proper nouns (geographic names) in the text, copy them
out into the notebook, transcribe them. Be sure to know the location of the objects
on the map.

Task 4. Compare and contrast the three main types of volcanoes (consider
size, composition, shape, and eruptive style).

Individual work

Task 1. Read the texts and translate them into Ukrainian (in written form).
Build up a list of key terms to the text.

Materials Extruded during an Eruption: gases and pyroclastic materials
Gases. Magmas contain varying amounts of dissolved gases (volatiles) held in
the molten rock by confining pressure, just as carbon dioxide is held in cans and bottles
of soft drinks. As with soft drinks, as soon as the pressure is reduced, the gases begin to
escape. Obtaining gas samples from an erupting volcano is difficult and dangerous, so
geologists usually must estimate the amount of gas originally contained within the
magma. The gaseous portion of most magmas makes up from 1 to 6 % of the total
weight, with most of this in the form of water vapor. Although the percentage may be
small, the actual quantity of emitted gas can exceed thousands of tons per day.
Occasionally, eruptions emit colossal amounts of volcanic gases that rise high
into the atmosphere, where they may reside for several years. Some of these eruptions
may have an impact on Earth’s climate.
The composition of volcanic gases is important because they contribute
significantly to our planet’s atmosphere. Analyses of samples taken during Hawaiian
eruptions indicate that the gas component is about 70 % water vapor, 15 % carbon
dioxide, 5 % nitrogen, and 5 % sulfur dioxide, with lesser amounts of chlorine,
hydrogen, and argon. Volcanoes are also natural sources of air pollution—some emit
large quantities of sulfur dioxide, which readily combines with atmospheric gases to
form sulfuric acid and other sulfate compounds.
Pyroclastic materials. When volcanoes erupt energetically they eject pulverized
rock, lava, and glass fragments from the vent. The particles produced are referred to as
pyroclastic materials (pyro = fire, clast = fragment). These fragments range in size from
very fine dust and sand-sized volcanic ash (less than 2 mm) to pieces that weigh several
tons. Ash and dust particles are produced when gas-rich viscous magma erupts
explosively. As magma moves up in the vent, the gases rapidly expand, generating a
melt that resembles the froth that flows from a bottle of champagne. As the hot gases
expand explosively, the froth is blown into very fine glassy fragments. When the hot
ash falls, the glassy shards often fuse to form a rock called welded tuff.
Somewhat larger pyroclasts that range in size from small beads to walnuts are
known as lapilli (“little stones”). These ejecta are commonly called cinders (2–64 mm).
Particles larger than 64 mm in diameter are called blocks when they are made of
hardened lava and bombs when they are ejected as incandescent lava. Because bombs
are semimolten upon ejection, they often take on a streamlined shape as they hurtle
through the air. Because of their size, bombs and blocks usually fall near the vent;
however, they are occasionally propelled great distances.
Some materials are also identified by their texture and composition. In
particular, scoria is the name applied to vesicular ejecta that is a product of basaltic

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