Volcanic Eruptions

Describe the types of pyroclastic materials and lava flows

The fragments of rocks that form during an eruption

Pyroclastic material is simply the material that forms and is expelled during a volcanic eruption. This material is expelled because of the viscosity of the felsic lava which traps gases such as carbon dioxide and water vapor. This causes an explosive eruption which results in pyroclastic material being ejected.

Classified Felsic Pyroclastic Material

Like everything else, scientists love to classify so naturally, the pyroclastic material erupting from the volcano is classified according to the sizes of the material. There are five basic types: volcanic ash, volcanic dust, lapilli, volcanic bombs and volcanic blocks.
Dome collapse and pyroclastic flow at Unzen Volcano
Pyroclastic Flow Unzen Volcano Kyushu, Japan. This pyroclastic flow killed 41 people.

Classified Mafic Lava Types

There are three basic types of mafic lava flows. These lava flows are pahoehoe, aa, and blocky lava. Pahoehoe is mafic lava that takes the shape of a rope. The word pahoehoe means "ropy" in Hawaiian. As it cools it forms a smooth, ropy texture. The second type of lava is aa. Aa is also a mafic lava. This lava forms as the crust deforms rapidly or grows too thick to form wrinkles, and instead breaks off into jagged chunks. The third type of lava is blocky lava. Blocky lava is also a mafic lava. This lava is very viscous and it causes it to break off into large chunks near the vent of the volcano.

Lava Flow at Volcano

Volcan en erupcion. Maravillas de la naturaleza.

Three Types of Volcanoes

Describe the three different types of volcanoes

Volcanoes are classified into three different types which are based on the volcanoe's cone. The shape of the volcano cone is dependent on the viscosity of the mafic magma and the viscosity of the felsic pyroclastic material. This material builds up along the main vent of the volcano. The funnel at the top of volcano is known as the crater, which forms from the volcanoe's eruptions. The three different types of volcanoes are shield volcano, cinder cone volcano, and composite volcano.

Calderas form in two ways

A caldera is a large, ciruclar depression that forms when the magma chamber below a volcano partially empties and causes the ground above to sink.

Identify four signals of an eminent volcano eruption

1. Changes in earthquake activity.

2. Temperature changes within the rock

3. Surface bulges

4. Changes in the amount and composition of gases