Plate tectonics Science / Africa, continental drift, Earth, Geological, Geology, Ocean, Plate tectonics, Research, Science, South America, Theory
Magnesium Chemical Element / Atomic Number, Carbohydrates, Chemical Compounds, Chemical Element, Chlorophyll, DNA, Element, Gray, Green, Magnesium, Metabolism, Metal, Pigment, Plants, RNA, Shiny
Pittsburgh City / City, Energy, Healthcare, Pennsylvania, Pittsburgh, River, Science, Sea, Software, State, Technology, United States, War, Waterway