view of Earth at WikiMapia USGS Geomagnetism Program NASA Earth Observatory Earth Profile by NASA's Solar System Exploration The size of Earth compared
known as "rare earth elements", a deprecated term. Regarding group membership of these elements, see here. Alkali metals, alkaline earth metals, transition
University Press - Bartleby. "Continent". McGraw-Hill Concise Encyclopedia of Earth Science (extracted from online McGraw-Hill Encyclopedia of Science and Technology)