a property possessed by some elements (e.g., uranium) in which streams of charged nuclear particles are emitted due to the…
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Radiocarbon dating
a process for determining the age of organic (carbon-containing) materials using the rate of radioactive decay of Carbon-14, also known…
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Radiometric dating
establishing an age based on changes in atomic structure (A1)
Reference course
an ideal course based on average wind and current conditions, charted before beginning a voyage in a traditional Hawaiian canoe…
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Relative humidity
the ratio between the amount of water vapor in the air currently and the highest amount of water vapor possible…
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Relative time scale
as in the geologic time scale, one that expresses age or length in relationship to other periods of time or…
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Revetment
a sloping type of shoreline armoring often constructed from large, interlocking boulders (C1)
Rhizome
a rootlike plant stem that grows underground or along the ground surface, is often thickened by deposits of reserve food…
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Runoff
water that flows across the land surface and into stream channels promptly after rainfall (R1)
Salinity
salt content of water (C3, M3)