Keywords

Precipitation with a higher concentration of acids than the typical value of natural rain water (5.4).  The high acidity is due to the dissolution of naturally-occurring and human-generated oxides of sulfur and nitrogen in the atmosphere.

Geological keywords, such as “granite”, “lake”.  The definitions are generally taken from the AGI Glossary of Geology.  Keywords with a geographic context (e.g. Cape Smith Fold Belt, Selwyn Basin, Grenville Province) are assigned to a separate category.