Carbon dating lesson plans
Two different trends can be seen in the tree ring series.
These marine reservoir effects vary over time as well as geographically; for example, there is evidence that during the Younger Dryas, a period of cold climatic conditions about 12,000 years ago, the apparent difference between the age of surface water and the contemporary atmosphere increased from between 400 and 600 years to about 900 years until the climate warmed again. For example, rivers that pass over limestone, which is mostly composed of calcium carbonate, will acquire carbonate ions.
During either a geomagnetic reversal or a global polarity excursion, production increases during the period when the geomagnetic field is weak.
It is fairly certain, though, that in the last 50,000 years there have been no geomagnetic reversals or global polarity excursions.
Photosynthesis is the primary process by which carbon moves from the atmosphere into living things.
Two different photosynthetic processes exist: the C3 pathway and the C4 pathway.
The effect is not necessarily confined to freshwater species—at a river mouth, the outflow may affect marine organisms.