VOLCANO

Group Member: 1. Aulia Y.2. Lintang Amiluhur3. Maula Akbar4. M. Andika Putra5. Vino Chandra6. Yohanes Agung C.

Lexicogrammatical Features

• Simple Present TenseA volcano is a vent which transfers molten rock known as magma from depth to the earth’s surface.

• Passive voiceFor example, a mid-oceanic ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates pulling apart

What is Volcano?

A volcano is a vent which transfers molten rock known as magma from depth to the earth’s surface. Magma erupting from a volcano is called lava and is the material which builds up the cone surrounding the vent.

Earth's volcanoes occur because its crust is broken into 17 major, rigid tectonic plates that float on a hotter, softer layer in its mantle. Therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging. For example, a mid-oceanic ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates coming together.

Type of Volcanoes

Cinder Cone:

These are the simplest type of volcano. They occur when particles and blobs of lava are ejected from a volcanic vent. The lava is blown violently into the air, and the pieces rain down around the vent. Over time, this builds up a circular or oval-shaped cone, with a bowl-shaped crater at the top.

Composite Volcano:

Composite volcanoes, or stratovolcanoes make up some of the world’s most memorable mountains: Mount Rainier, Mount Fuji, and Mount Cotopaxi, for example. These volcanoes have a conduit system inside them that channels magma from deep within the Earth to the surface. They can have clusters of vents, with lava breaking through walls, or issuing from fissures on the sides of the mountain. With all this material coming out, they can grow thousands of meters tall.

Shield Volcano:

These are large, broad volcanoes that look like shields from above – hence the name. The lava that pours out of shield volcanoes is thin, so it can travel for great distances down the shallow slopes of the volcano. These volcanos build up slowly over time, with hundreds of eruptions, creating many layers. They’re not likely to explode catastrophically.

Lava Domes:

Volcanic or lava domes are created by small masses of lava which are too viscous (thick) to flow very far. Unlike shield volcanoes, with low-viscosity lava, the magma from volcanic domes just pile up over and around the vent. The dome grows by expansion of the lava within, and the mountain forms from material spilling off the sides of the growing dome. Lava domes can explode violently, releasing a huge amount of hot rock and ash.

How did it happen?

Volcanic eruptions happen when lava and gas are discharged from a volcanic vent. The most common consequences of this are population movements as large numbers of people are often forced to flee the moving lava flow. Volcanic eruptions often cause temporary food shortages and volcanic ash landslides called Lahar.

Although the Earth’s mantle is solid rock, it’s under high pressures and temperatures, and this causes rock to melt and squeeze out of cracks in the rock. The magma collects into vast chambers beneath the Earth’s crust. Since this magma is less dense than the surrounding rock, it “floats” up to the surface, seeking out cracks and weaknesses in the rock. When it finally reaches the surface, we see this as an eruption.

How about the effects?

• Volcanic GasesWater vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide.

• Acid RainThis effect, together with increased stratospheric chlorine levels from chlorofluorocarbon pollution, generates chlorine monoxide (ClO), which destroys ozone (O3).