"Volcano" PPT

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Hunan Education Edition Sixth Grade Science Volume 1, Volcano PPT

Part I: The harm and value of volcanic eruptions

The dangers and value of volcanic eruptions

1. Harm

(1) Environmental hazards: A large amount of volcanic ash ejected by a volcanic eruption and heavy rain combine to form mudslides. Mudslides can destroy roads and bridges, flood nearby villages and cities, and leave countless people homeless. Mud formed from mud and rock debris can flood entire cities.

(2) Debris pollution: Pyroclastic debris is the condensed debris of magma emitted by volcanoes, as well as the volcanic debris ejected into the air from the volcanic channels and the four walls of the rock debris. The heavy ones fall near the volcano crater, and the light and small ones fall into the air. Either they are blown by the wind and settle hundreds of kilometers away, or they rise to the stratosphere and circulate with the atmosphere. Volcanic eruptions are hot volcanic ash flows mixed with water (heavy rain in volcanic areas, nearby rivers and lakes, etc.) to form dense lahars. Ash flows and mudflows are both disastrous.

2. Value

(1) Increase resources: Generally speaking, volcanic resources are mainly reflected in its tourism value, geothermal utilization and volcanic rock materials. Volcanoes and geothermal energy are twin brothers. Where there are volcanoes, there are generally geothermal resources. Geothermal energy is a cheap new energy source that is pollution-free and has been widely used. Nowadays, the application of geothermal energy can be seen in medical treatment, tourism, agricultural greenhouses, aquaculture, civil heating, industrial processing, and power generation.

Volcanic activity can also form a variety of minerals, the most common of which is the formation of sulfur ores. Basalt erupted on land often crystallizes into natural copper and calcite, and basalt erupted by submarine volcanoes often forms large-scale iron ore and copper deposits.

In addition, the formation of masonry as we know it is also related to volcanoes. Basalt is the most widely distributed volcanic rock, and it is also a good building material. The smelted basalt becomes "cast stone", which can be made into various plates, utensils, etc.

The biggest characteristics of cast stone are that it is hard and wear-resistant, acid-resistant, alkali-resistant, non-conductive and can be used as insulation material.

(2) Rebirth: Volcanic eruptions have a profound impact on the natural landscape. Land is the world's most precious resource because it breeds all kinds of plants to support all things. If a volcanic eruption can cover farmland with volcanic ash less than 20 centimeters thick, it will be a great blessing for farmers, because the volcanic ash is rich in nutrients and can make the land more fertile.

(3) Create wonders: Geysers are a natural phenomenon in the later stages of volcanic eruptions. When the high temperature in the ground heats the groundwater to a certain pressure, water and steam will rush out from the spout. When the pressure decreases, it will stop spraying and enter the next process. The geysers in Yellowstone Park in the United States are very famous. Some of them can shoot to a height of more than 100 meters, and their roars like roaring waves are thrilling.

There is an "underground forest" in Heilongjiang Province, my country, which evolved from seven extinct volcanic craters. Due to the fertile soil formed by the weathering of volcanic eruptions, some plants settled in this large pit. This kind of underground forest is rare.

Volcano PPT, Part 2: Introduction to famous volcanoes

Introduction to famous volcanoes

Mauna Loa: Located in the center of the Hawaiian Islands, with an altitude of 4,170 meters and a height of more than 9,300 meters from the sea floor. It is an active volcano and has erupted approximately 35 times in the past 200 years. There are still several pot-shaped craters and large calderas up to 2,700 meters wide on the top of the mountain. There are often white clouds lingering on the top of the mountain, appearing and disappearing. Mauna Kea in the north of the island is 4,205 meters above sea level and is the highest peak in Hawaii. The world's highest observatory is located on the top of this mountain.

Mount Fuji, Japan: Located at the junction of southeastern Nishi Prefecture and Shizuoka Prefecture, Japan, with an altitude of 3,776 meters, it is the highest peak in Japan. The top of the mountain towers into the clouds and is covered with snow.

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Update Time: 2024-11-24

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