Volcanic origin, surrounded by coral reefs; relatively flat coralline limestone plateau (source of most fresh water), with steep coastal cliffs and narrow coastal plains in north, low hills in center, mountains in south
Tropical marine; generally warm and humid, moderated by northeast trade winds; dry season (January to June), rainy season (July to December); little seasonal temperature variation
Nationality: Guamanian(s) (US Citizens)
Population: 161,001 (July 2014 est.)
Languages: English 43.6%, Filipino 21.2%, Chamorro 17.8%, other Pacific island languages 10%, Asian languages 6.3%, other 1.1% (2010 est.)
Roman Catholic 85%, other 15% (1999 est.)
The economy depends largely on US national defense spending, tourism, other services. Total US grants, wages and salaries, and procurement outlays amounted to approximately $1.6 billion in 2010. Over the past 30 years, tourism has grown to become the largest income source following national defense.