Note: if one letter is incorrect in a term, that part of the puzzle will be graded as a missed answer. - Across 2) This is the ceasing of the existence of any particular species. 6) This is a geologic event that occurs when a large area of ground flows downward. It may be induced by erosion, earthquakes or volcanic eruptions. 7) This is a sudden, natural or man-made situation where change and destruction may occur without prior knowledge or preparation. A sudden, violent event. 8) This is a violent rotating column of air extending from a thunderstorm to the ground. 9) This is the movement of individuals out of a population. 10) The number of individuals of a species per unit area. - Down 1) The number of individual organisms of a particular species in a group. 3) All the individuals of a species that live together in one place at the same time 4) This is tropical storm system that circulates around an area of low pressure. 5) This is a landform that is formed by the eruption of magma through a vent