WR 327
Technical Report
Spring \'99


In this report I plan to discuss the geological event of volcanic eruptions and the disasters they cause. To me, this is a fascinating topic and timely seeing how the 19th anniversary of the eruption of Mt. St. Helens is upon us. I hope to inform people of the mass destruction that is caused by the eruption of a volcano. The scope of my report will be limited to: 1) describing what comes out of a volcano, 2) explaining the seven different types of volcanoes, 3) explaining the five types of volcanic eruptions, and 4) explaining the disasters they can cause people. The procedure for completing this report first started by watching educational television programs that featured volcanoes and the upcoming anniversary of the eruption of Mt. St. Helens. From there, I decided that the topic of volcanoes would be a good subject for my analytical report. Then I began my research, first looking online for websites that contained information and pictures of volcanoes. After this, I looked for publications about volcanoes in the library, finding many books that pertained to my topic. Having an abundance of data, I began to sort through all of it and found what I thought to be the most informative. I then prepared an outline of the subjects I wanted to write about and arranged the data and visuals to fit my outline. And of course from there, I began to write this report using the technical writing methods taught during lecture and described in the book.

Collected Data

If we look through volcanoes we can view the interior of the earth. More than just lava flows are spewed out of volcanoes when they erupt. The three main components that erupt out of a volcano are: lava, ash, and bombs. When all three of these components lump together, the solid fragments are called pyroclastics. Pyroclastic rocks can be erupted in two different ways: they can be airfall deposits or pyroclastic flows.
There are seven different types of volcanoes: Submarine volcanoes; Ridges and vents; Shield volcanoes; Lava plateaus and Flood basalts; Lave domes; Composite volcanoes; Cinder and Scoria cones; and Calderas. Each of these volcanoes is found in different geographical locations and have different eruptions. Along with different types of volcanoes, there are also different types of eruptions. The five eruption types are: Pelean, Vulcanian, Strombolian, Hawaiian, and Icelandic. These volcanoes have different levels of explosiveness, and their eruptions occur due to their geographic location.
A volcanic hazard is destructive natural process that has a probability of reoccurring. Losses from volcanoes include: people\'s lives, property, livestock, and the productive capacity of the area. The factors of predicting volcanic activity are: the longer a volcano is inactive, the greater the chances are for it to become active; eruptive behavior may change with time; and some hazards are indirectly related to an eruption, making it difficult to forecast. Being informed of volcanoes in your area and knowing cautionary steps can save your life.
What Comes out of Volcanoes?

Volcanoes are dark windows to the interior of the Earth (Decker 104). Volcanic products are our only direct samples of the Earth\'s composition from deeper levels. Most people think that lava flows are the only products spewed from volcanoes, but actually volcanic ash and larger solid fragments, called cinders and blocks, form the major products of observed volcanic eruptions (Decker 104). The three components that erupt from a volcano are: lava ash, and bombs. The volcanic debris that lumps together all the sizes of solid fragments is called pyroclastics (See Figure 1). Pyroclastics come from three sources: magma that is cooled and broken into fragments by expanding gases at the moment of eruption; fragments of old crater walls which are ripped loose in explosive eruptions; and clots of liquid lava thrown into the air which cool during their flight. Pyroclastic rocks are set apart by the general size of fragments. Volcanic dust is fine; volcanic ash is gritty, with particles up to the size of rice; cinders include pieces as big as Ping-Pong balls; and blocks cover all other fragments up to the size of a house. Volcanic bombs are block-sized clots of liquid lava thrown from erupting vents. Pyroclastic rocks can be erupted in two different ways: they can be airfall deposits