Most of the Earth's land has been scorched by fire at some time in the past. Although causing many a tragedy, fire is considered part of a natural ecosystem cycle . The year 2000 fire season in the continental United States has been one of the most active on record, burning an area similar in size to New Jersey . Large forest fires on Earth are usually caused by lightning and can be visible from orbit . Above , stunned Elk avoid a fire sweeping through Montana 's Bitterroot Valley by standing in a river.
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