"If all the trees fall down" PPT

Hunan Education Edition sixth grade science volume 1, if the big trees fall down PPT courseware

If all the big trees fall down PPT, part one: serious consequences of forest destruction

Serious consequences of forest destruction

Sandstorm is a general term for both sandstorms and dust storms. It refers to a serious sandstorm weather phenomenon in which strong winds blow up a large amount of sand and dust material from the ground and roll it into the air, making the air particularly turbid and with horizontal visibility less than one thousand meters. Sandstorms refer to sandstorms caused by strong winds blowing large amounts of sand into the ground; dust storms are storms caused by strong winds carrying large amounts of dust and other fine particles into high altitudes. Due to its unique geographical environment, northwest China is also an area where sandstorms frequently occur. The main source areas are the Gurbantunggut Desert, Taklimakan Desert, Badain Jaran Desert, Tengger Desert, Ulan Buh Desert and Mu Us Desert. .

If all the big trees fall down PPT, Part 2: Serious consequences of sandstorms

Serious consequences of sandstorms

1. Deterioration of the ecological environment. When sandstorms occur, the sand, stones and floating dust wrapped in strong winds spread everywhere. The air in the passing areas becomes turbid, causing choking noses and eyes, and an increase in the number of respiratory and other diseases.

2. The impact on production and life can easily make people feel depressed and reduce work and study efficiency. In mild cases, a large number of livestock can be infected with respiratory and gastrointestinal diseases. In severe cases, it can lead to the death of a large number of "spring fatigue" livestock and scrape away fertile farmland, seeds and seedlings. Sandstorms will also intensify wind erosion and desertification of surface soil, covering plant leaves with thick dust, affecting normal photosynthesis and causing crop yield reductions. The sandstorm also caused the temperature to drop sharply. The sky was like a parasol, and the ground became dark and cold under the shadow.

3. Loss of life and property

4. Impact on traffic safety Sandstorm weather often affects traffic safety, causing planes to be unable to take off or land normally, and causing glass breakage, suspension or derailment of cars and train carriages.

5. Harmful to human health When people are exposed to sand and dust weather, dust containing various toxic chemicals, germs, etc. can penetrate through layers of protection and enter the mouth, nose, eyes, and ears. If the dust containing a large amount of harmful substances is not cleaned up in time, it will cause damage to these organs or the bacteria will use these organs as entry points to cause various diseases.

If all the big trees fall down PPT, the third part: Disaster

acid rain

Acid rain belongs to air pollution and refers to rain, snow or other forms of precipitation with a pH value less than 5.6. Rainwater is contaminated by acidic gases present in the atmosphere. Acid rain is mainly caused by man-made emissions of large amounts of acidic substances into the atmosphere.

harm:

1. The severity of urban air pollution has changed the laws of seasonal changes and diurnal changes, and can be roughly divided into two categories: coal type and petroleum type.

2. As a result of the increase in urban cloud cover, the sunshine hours and solar radiation in urban areas have decreased.

3. Acid rain can cause soil acidification.

4. Acid rain can dissolve the hardened cement on the surface of non-metal building materials (concrete, mortar and lime sand bricks), causing voids and cracks, resulting in reduced strength and damage to the building.

flood

Floods are disasters caused by surges in water levels in rivers, lakes, and reservoirs, overflowing or bursting of dams, and the inflow of water.

Hazards: my country has a vast territory, and about 3/4 of the land area is subject to flood disasters of different types and degrees. The eastern plain areas that are the focus of urban flood control in flood control, such as the middle and lower reaches of the Liaohe River, the northern plain of the Haihe River, the middle reaches of the Yangtze River (Jianghan Plain, Dongting Lake area, Poyang Lake area and the area along the river), the Pearl River Delta, etc. They all have a common geographical feature. That is, it is located in the low-lying areas around lakes and on both sides of rivers and estuaries. In addition, the junction between some mountainous areas on the southeastern coast and the coastal plain is also an area with greater flood risk. Most of them are in flood plains which are most affected by flooding. Our country has nearly 1 million square kilometers of flood plains. More than 60% of the country's industrial and agricultural output, 40% of the population, 35% of arable land, more than 600 cities, major railways, highways, oil fields, and many industrial and mining enterprises are threatened by floods. .

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"If all the trees fall down" PPT download:

Hunan Education Edition Sixth Grade Science Volume 1, If ​​the Big Trees Fall Down PPT Download, Part One: Poetry Appreciation In a dense forest, a group of cute little trees are having a conversation: There is only one earth, lose it, where will we go? To find a home? us..

"If all the trees fall down" PPT:

Hunan Education Edition Sixth Grade Science Volume 1, If ​​the Big Trees Fall Down PPT, Part One: Game Method Game Method: 1. Each student plays a creature. 2. Connect each two creatures with a line that has a food connection. 3. If a creature withdraws, all with...