Impact craterAn impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Lunar impact craters range from microscopic craters on lunar rocks returned by the Apollo program and small, simple, bowl-shaped depressions in the lunar regolith to large, complex, multi-ringed impact basins.
Ecosystem healthEcosystem health is a metaphor used to describe the condition of an ecosystem. Ecosystem condition can vary as a result of fire, flooding, drought, extinctions, invasive species, climate change, mining, fishing, farming or logging, chemical spills, and a host of other reasons. There is no universally accepted benchmark for a healthy ecosystem, rather the apparent health status of an ecosystem can vary depending upon which health metrics are employed in judging it and which societal aspirations are driving the assessment.
Lake ConstanceLake Constance (Bodensee, ˈboːdn̩ˌzeː) refers to three bodies of water on the Rhine at the northern foot of the Alps: Upper Lake Constance (Obersee), Lower Lake Constance (Untersee), and a connecting stretch of the Rhine, called the Lake Rhine (Seerhein). These waterbodies lie within the Lake Constance Basin (Bodenseebecken) in the Alpine Foreland through which the Rhine flows. The lake is situated where Germany, Switzerland, and Austria meet. Its shorelines lie in the German states of Baden-Württemberg and Bavaria, the Swiss cantons of St.
