Bore 



A tidal wave with an abrupt front often three or more 

 feet high, advancing upstream in a narrow river estuary. 



Boreal Forest 



The forest consisting chiefly of conifers extending across 

 northern North America from Newfoundland to Alaska. 



Boreal Life Zone 



One of Merriam's life zones including northern North 

 America, Boreal forest and Tundra vegetation, bounded at 

 its southern limit by growth-season accumulated temperature 

 above 43 F. of 1 0,000 F. and a mean daily temperature of 

 64.4 F. for the six hottest weeks. Subdivided into the Arctic, 

 Hudsonian, and Canadian life zones. 



Boreal Period 



The climatic period from about 7500 to 5500 B. C., 

 characterized by warm, dry conditions; preceded by the 

 Preboreal period (8000-7500 B. C.) with variable climate, and 

 the Subarctic period (9000-8000 B. C.) with cold, dry climate, 

 cf. Sub-boreal period. 



Bottom Deposits 



Organic and inorganic materials deposited beneath water 

 and upon the original basin or channel floor. 



Bottom Fauna 



Animal components of the Benthos (q. v.). 



Bottomland 



See Flood plain. 



Boulder-clay 



Unstratified clay intermixed with many stones, deposited 

 by glaciers, cf. Till, Drift. 



Brachypterous 



Refers to organisms with short wings. 



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