题型：阅读理解 题类：常考题 难易度：普通
广东省梅州市丰顺县2021届高三上学期英语第一次质检试卷
Wildfires can burn acres of land—and consume everything in their way—in mere minutes. On average, more than 100,000 wildfires clear 4 million to 5 million acres of land in the U.S. every year.
In recent year wildfires have burned up to 9 million acres of land. A wildfire moves at speeds of up to miles an hour, consuming everything—trees brush, home, even humans—in its path.
There are three conditions that need to be present in order for wildfire to burn, which firefighters refer to as the fire triangle: fuel, oxygen, and a heat source. Fuel is any flammable material surrounding a fire, including trees, grasses, brush and even homes. Air supplies the oxygen a fire needs to burn. Heat sources help spark the wildfire and bring fuel to temperatures hot enough to catch fire. Lightning, burning campfires or cigarettes, hot winds, and even the sun can all provide much heat to spark a wildfire.
Although four out of five wildfires are started by people, nature is usually more than happy to help fan the flames. Dry weather and drought change green vegetation into dry, flammable fuel; strong winds spread fire quickly over land; and warm temperatures encourage combustion. When these factors come together all that's needed is spark—in the form of lightning, a downed power line, or a burning campfire or cigarette—to start a fire that could last for weeks and consume tens of thousands of acres.
These violent wildfires occur around the world, but they are most common in the US West where heat, drought, and frequent thunderstorms create perfect wildfire conditions.
Although often harmful and destructive to humans, wild fires play an important role in nature. They also remove disease—ridden plants and harmful insects from a forest ecosystem.
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