Fire & Characteristics of Wildfire

Transcription

1 Fire & Characteristics of Wildfire Curriculum Links: Grade 7 Physical Science--Heat and Temperature (HT) Objectives In this lesson students will develop an operational definition of wildfires. They will list the three components necessary for fire. They will understand the concepts of ignition. Materials Picture of a forest fire or fire prevention poster Drawing of the fire triangle or model of one Fire Triangle Worksheet one per student Poster(s) of fires given different Fire Weather Index or Rank to show different intensities. Explore If possible show students a picture of a forest fire or fire prevention poster. Ask the students if they can tell you what the meaning of a wildfire is. Give them a hint if necessary asking what is the difference between a house fire and a wild fire. Definition: A wildfire is an uncontrollable fire spreading through vegetative fuels, exposing and possibly consuming structures. They often begin unnoticed and spread quickly and are usually signaled by dense smoke that fills the area for miles around. Explain that wildfire is a natural part of forests and grasslands in Saskatchewan. Fire has been used for years to clear land, improve habitat, create dwellings free of vegetation and for other constructive purposes. The benefits of fire have been known to wildfire managers for the last few decades but the risk and liability involved with setting fires drastically reduced the number of prescribed burns that were set and the number of fires that were allowed to burn freely. Therefore, a large accumulation of old growth forest with a vast amount of litter and down material created the opportunity for an extreme fire situation. In the last 30 years or so, wildfire managers have gotten much more efficient at controlling wildfires and have also integrated an observation zone. This means that fires that are burning in areas that have nothing of value, not including areas such as commercial timber and communities, are allowed to burn until it goes out on its own or encroaches on a value and must be extinguished. An aggressive fire suppression program has been relatively successful in preventing and controlling fires, especially near communities resulting in Forestland, Parkland and Grassland. Benefits: - A wildfire is the earth s way of rejuvenating it s self. Though the initial burn of a fire looks to be destructive there are many benefits that arise from the burning of an area. - A burn can rid an area of disease and insect infection. - Create habitat for new animals such as raptors, moose, elk, grasshoppers, woodpeckers, etc. - Increase nutrients and other chemicals in the soil for vegetation regrowth and success. (This will depend on the depth of burn and amount of biomass in the area.) - Allows species such as Pine to reproduce. (This is done by releasing the cone from a resinous layer. It is melted off during a fire and the seeds are then released.) These cones are known as serotinous. - Remove some of the earth s old growth forest.

2 Fires actually renew the forest setting the stage for new growth. Most plants and animals in the forest are well adapted to fires; they have evolved strategies to live with fire. A fire in the forest will burn away surface material and sometimes expose mineral soil for seeds to take root. It also releases nutrients needed for plants to grow. Downfalls of a wildfire: - Loss of habitat (short term), - Destruction of property, - Loss of life (both human and animal), - Loss of plant life, - Animals lose their homes (be displaced), - Over population of another area, - Destruction of trees, Loss of commercially valuable timber - Aesthetics to the area Some effects due to a wildfire are: - Landslides, - Erosion, - Flash floods, - Ash flows and, - A decrease in water quality. ** The above effects are not so much of an issue in Saskatchewan as it is in the mountainous regions and will be reliant on soil type. In Saskatchewan there is some soil erosion but not a lot. ** Yet fires, although they may be good to renew the forest, also must be controlled. Wildfires must always be suppressed when they threaten human life, commercial areas and property. (A commercial area refers to mining, forestry operations, high value timber and other natural resource extraction areas.) This task is appointed to Wildfire Management Branch of Saskatchewan Ministry of Environment. They will use a values at risk approach to decision-making relating to prioritizing fire suppression activities ensuring that human life and safety receive and maintain the highest priority. This approach will be used on lands where Wildfire Management has legislative responsibility (everywhere in the province of Saskatchewan except for the national park) for fire suppression and also to prioritize requests for assistance from other ministries, governments, municipalities, industry and organizations. (Policy #311 for Wildfire Management) Everything on earth has a temperature at which it will burst into flames. This temperature is called a materials flash point. Wood s flash point is 300 C. When wood is heated to this temperature, it releases hydrocarbon gases that mix with oxygen in the air, combust and create fire. There are three components needed for ignition and combustion to occur. A fire requires what three things? (Fuel to burn, air to supply oxygen, and a heat source to bring the fuel up to ignition temperature) Tell the students we often represent these three things in what is referred to as the fire triangle. (Teacher can draw an example of this on the board or have a poster or model of this to show to the students.) To put a fire out you must remove one of these three elements. Ask the students what they think would be the easiest thing to remove. Firefighters using water are both trying to suffocate the fire and reduce the heat element. Airplanes dropping fire retardant in an effort

3 to cover fuel sources so they no longer burn. Back burns are a way of getting rid of fuel that will keep a fire going. The trick is to know what will be the most efficient and safest method of putting out an unwanted fire. Fuel: - Fuels, as defined by wildfire, is any combustible material found on the landscape. This includes live trees, dead trees, dry grass, branches, needles, leaves and moss. - Fuel is one of the biggest factors when dealing with fire. The fuels will tell us how the fire will burn, the rate of consumption and the areas of high risk. - There are several components of fuel that must be taken into consideration. - Fuel Moisture - Chemical Content - Fuel Temperature - Size and Shape - Fuel Load - Compactness - Horizontal Continuity - Vertical Continuity - The characteristics of the fuel are critical. If the fuel itself reacts with heat then the likelihood of the fuel burning is higher. - On the other hand, if a fuel is very moist and has little reactions to heat, it will be harder to burn. - This is why in a burnt area you will see patches of unburned materials. - FIRE WILL TAKE THE PATH OF LEAST RESISTANCE! Oxygen: - Fire needs oxygen to grow. That s why smothering a fire is an effective means of suppressing a fire. - Basically, fire can not breathe or go on without the presence of oxygen. - A big concerns when dealing with fires is the wind changing directions. This is due to the overall shift of the fire and the location of the suppression crews that are out fighting the fire. With all of the weather systems that are used to predict what the weather will be like, it is not often that this happens with negative consequences. Heat: - Heat is a key component of the triangle. Without heat the fire would not be able to dry out the materials in front of it to continue to burn. - Also, heat can be looked at as the ignition source. A lighter, match, lightning, etc. - A fire s intensity (a high or extreme degree, as of cold or heat) will determine the amount the fire will consume. - If a fire is extremely intense then the fire will burn even the most resistant materials. At this point you can visually show student that the removal of oxygen will put a fire out. Have a candle in a jar. Light the candle and place the lid on the jar. As soon as the flame uses up the available oxygen in the jar it will go out. You can get the students to guess how many seconds it will take for the fire to use up the oxygen. Next you can relight the candle and let it burn with the lid off to emphasis the difference. Wildfire firefighters train in fire fighting operations, especially emphasizing safety and survival. They also learn fire fighting techniques, fire behavior, weather, environmental protection and the use and care of firefighting equipment. Keep in mind that a Wildland firefighter is only trained to extinguish

4 Wildland fires and urban firefighters are trained to extinguish structural fires. It might not seem that there would be that much to learn about putting out fires. Wildfire fighters must learn about the different types of wildfires. These consist of: 1. Surface fire this type of fire burns along the forest floor consumes litter and humus, moving slowly, kills herbaceous plants and shrubs, and scorches the bases and crowns of trees. This is the most common type. Surface fires can move very quickly, especially in fine fuels such as grass and when there are high winds. 2. Ground fire this type of fire burns below the forest floor in the humus (organic material) layer down to the mineral soil. It is usually started by lightning strikes but when a fire is already burning in the area, it can find it s way to the organic layer and smolder. Ground fires kill most plants at their roots in the organic layer, burn slowly and can generate high temperatures. Ground fires are persistent and take a lot of effort to ensure that they are out, if they are not fully extinguished it may re-ignition and create surface fires. 3. Crown fires these fires spread rapidly by wind. A crown fire is started by surface fires that are fueled by accumulations of organic matter and whipped by wind. This will often scorch and ignite tree crowns. Also, the fire could reach the top of the trees by igniting ladder fuels (fuels such as branches and party fallen trees) to reach the top. Conifers are most susceptible to these fires because of their flammable foliage and their relatively even age stands. Sparks and burning debris may start new surface fires far away from the site of the crown fire. Ask the students if they know what would be the leading cause of wildfires in Saskatchewan? Explain to them that 50% of fires are started by people and 50% are lightning caused fires. Negligent human behavior, such as smoking in forested areas, improperly extinguishing campfires, ATV s, brush burning, stubble burning, etc. cause many of these fires. Lightning also causes forest fires but with today s global information systems personnel can detect lightning strikes quickly and pinpoint risk areas for fire. Below you will find the Fire Triangle Worksheet have the students complete it to reinforce what they learned. Conclusion In this class we explored what wildfires are. We learned what is necessary for fires to burn and with that knowledge we learned that eliminating one of the necessary components we can extinguish unwanted fires. Next time you hear about wildfires in the province pay close attention to what the reporters are saying about the strategies the firefighters are using to try and extinguish the blaze. For more information visit the Wildfire Management website at: Worksheet below..

5 Fire Triangle Worksheet Name: 1. Fires need three components in order to burn. This is known as the fire triangle. Draw a triangle below and label each of the three sides with the words for each of the three parts. 2. Initially, the heat is provided by an ignition source, which can be natural or human. Name one natural caused source of heat for fire ignition and three human caused sources. natural 3. Fires need fuel to burn. Name three potential fuels you might expect to find in a forest. 5. If you cut off any off any one of the three elements-heat, fuel, and oxygen-a fire will not burn. What are some ways that firefighters might cut off each of the three parts of the fire triangle?