Science.gov, a comprehensive listing of authoritative U.S. government information in the sciences, offers this well-organized, annotated listing of earth science and oceanography websites and electronic documents. In addition to their list of general information, the following narrower topics are easy to find from the main page:

• Climate, Weather, and Meteorology
• Earthquakes, Floods And Other Natural Disasters
• Geology And Land Forms
• Mapping and Cartography
• Oceans and Oceanography
• Snow, Ice, and Permafrost
• Soil
• Water and Hydrology

In addition to browsing by narrower subject and by title, USA.gov's sophisticated search engine is available, with lots of helpful limiting and filtering options.