Volcanoes can cause widespread destruction and consequent disaster in several ways. The effects include the volcanic eruption itself that may cause harm following the explosion of the volcano or the fall of rock. Second, lava may be produced during the eruption of a volcano. As it leaves the volcano, the lava destroys many buildings, plants and animals it encounters. Third, volcanic ash generally meaning the cooled ash - may form a cloud, and settle thickly in nearby locations. When mixed with water this forms a concrete-like material. In sufficient quantity ash may cause roofs to collapse under its weight but even small quantities will harm humans if inhaled. Since the ash has the consistency of ground glass it causes abrasion damage to moving parts such as engines. The main killer of humans in the immediate surroundings of a volcanic eruption is the pyroclastic flows, which consist of a cloud of hot volcanic ash which builds up in the air above the volcano and rushes down the slopes when the eruption no longer supports the lifting of the gases. It is believed that Pompeii was destroyed by a pyroclastic flow. A lahar is a volcanic mudflow or landslide. The 1953 Tangiwai disaster was caused by a lahar, as was the 1985 Armero tragedy in which the town of Armero was buried and an estimated 23,000 people were killed.
At first, you might not know which approach is best for your topic. In general, if it is difficult to make a clear distinction between cause and effect, the group approach is probably best. On the other hand, if there is a direct relationship between cause and effect, each cause has a clear effect, then the alternating chain approach might be better. In many cases, you might want to combine both types at different times. First you must get your ideas down on paper and then you will see which approach seems best for you.
"The US economy, because it's so energy wasteful, is much less efficient than either the European or Japanese economies. It takes us twice as much energy to produce a unit of GDP as it does in Europe and Japan. So, we're fundamentally less efficient and therefore less competitive, and the sooner we being to tighten up, the better it will be for our economy and society."
"There are thousands of different chemicals in the environment that may cause adverse human health effects. Little is known about the toxicological properties of most of these chemicals..."
At this point, students should have enough ideas, words, and sentences listed on their worksheet and in their notes to begin writing well organized paragraphs. The teacher should remind them to include examples to support each of their cause and effect relationships. Once the first draft is completed, the teacher may opt to do peer editing in the next class before students rewrite their second drafts.
Look at the lists above. Think about the relationship of the items in your lists and arrange them in a reasonable order. Do some causes or effects happen before others? Put each cause and each effect in some kind of order by replacing numbers in your list.