Curated OER
Volcanoes
A thorough description of volcanoes appears in this Earth science worksheet. Students read facts about volcanoes and answer 20 multiple choice comprehension questions. The answers appear at the end of the worksheet.
Encyclopedia of Earth
Encyclopedia of Earth: Physics & Chemistry: Carbon Dioxide
Explains what carbon dioxide is, where it is found, sources of it, and describes human activities that contribute to carbon depletion and increased levels of carbon dioxide in the atmosphere. (Updated: February 22, 2013)