natural boundary
31public boundary — A natural boundary; a natural object or landmark used as a boundary or as a beginning point for a boundary line …
32river boundary — A natural boundary of lands in private ownership, the exact location of which must depend upon whether the title to the bed of the river is in the state or the riparian owners and the view taken in the particular jurisdiction concerning the… …
33artificial boundary — A boundary erected by man, as distinguished from a natural boundary, such as a stream …
34Cross-boundary subsidy — Alaskan boreal forest in Yukon National Wildlife Refuge Cross boundary subsidies are caused by organisms or materials that cross or traverse habitat patch boundaries, subsidizing the resident populations. The transferred organisms and materials… …
35Cross-boundary subsidies — are caused by organisms or materials that cross or traverse habitat patch boundaries, subsidizing the resident populations. The transferred organisms and materials may provide additional predators, prey, or nutrients to resident species, which… …
36Consolidated Natural Resources Act of 2008 — Full title A bill to authorize certain programs and activities in the Department of the Interior, the Forest Service, and the Department of Energy, to implement further the Act approving the Covenant to Establish a Commonwealth of the Northern… …
37Elliptic boundary value problem — In mathematics, an elliptic boundary value problem is a special kind of boundary value problem which can be thought of as the stable state of an evolution problem. For example, the Dirichlet problem for the Laplacian gives the eventual… …
38Planetary boundary layer — Depiction of where the planetary boundary layer lies on a sunny day The planetary boundary layer (PBL), also known as the atmospheric boundary layer (ABL), is the lowest part of the atmosphere and its behavior is directly influenced by its… …
39Maritime boundary — Graphic representation of maritime zones …
40K–T boundary — The K T boundary is a geological signature, usually a thin band, dated to 65.5 ± 0.3 (mya). [ [http://www.stratigraphy.org/cheu.pdf International commission for Stratigraphy] ] K is the traditional abbreviation for the Cretaceous Period, and T is …
