What do carbon isotopes tell us about atmospheric O2 levels?
What will be an ideal response?
Carbon isotope values in carbonates indicate the rate of organic carbon burial or, more precisely, the fraction of outgassed carbon that is buried as organic carbon (as opposed to carbonates). Since organic carbon burial leads to net O2 production on time scales of less than millions of years, the carbon isotope data can be used to determine relative rates of net O2 production. Isotopically heavy C indicates fast rates of organic carbon burial and high levels of O2 production. But, curiously, there is little or no secular change in carbon isotope values throughout geologic time. This is usually taken to mean that the rise of O2 was caused by changes in the sinks for O2, not by changes in the source. Frankly, however, there is little agreement on what exactly caused O2 to rise when it did.
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Groundwater mining
A. lowers the water table. B. creates perched water tables. C. reduces the zone of aeration. D. digs out the water instead of pumping it.
What instrument used during the early part of the twentieth century improved the accuracy of ocean depth
measurements compared to the rope and weight? a. Remotely operated underwater vehicle b. Acoustic Doppler current profiler c. Satellite d. Autonomous underwater vehicle e. Echo sounder
The collision efficiency:
A) is approximately one regardless of drop size. B) is affected by the compression of air just below the collector drop. C) is governed primarily by the temperature of the air. D) is highest for droplets of equal or nearly equal size.
________ is a metal with a wide range of uses; it has received considerable attention in recent years because of its growing importance in batteries used in cell phones, laptop computers, and hybrid and electric-powered vehicles
A) Lithium B) Electrolyte C) Copper D) Platinum E) Rarearthium