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From Outer Space
Clues to the Past
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America ancient objects animals anthropologists archaeological archaeologists archaeomagnetic atoms carbon dioxide carbon-14 dating carbon-14 testing centuries charcoal chronology civilization climates clue culture dating method dating objects dating the past Djoser earth earth's magnetic electrons elements eruption excavated Fertile Crescent fourth Ice Age Friedman and Smith geographic north Geological geologists glaciers grain Gregorian calendar half-life human hydration layers Ice Age investigators Jarmo Kenya known dates land lava Lewisville Libby lived lotus seeds magnetic field Mayan measure method for dating microns2 Mount Mazama neutrons Newberry Crater obsidian obsidian artifacts ocean floor piece plants prehistoric primitive protons radioactive radiocarbon dating radiocarbon laboratories relics remnant magnetism Russell Cave sample scholars scientific dating scientific methods scientists sediments snow south poles specimen storage tube surface technique temperature thermoluminescent Tikal timetable tion true magnetic north U.S. Geological Survey University volcano wood