What are stromatolites, and why are they important in Earth history? What will be an ideal response?
Stromatolites are blue-green algae that trap sediment. They are common in some Proterozoic rocks,
but the oldest are in 3.3 to 3.5 billion-year-old rocks. Stromatolites are important because the
atmosphere of the Paleoarchean had no free oxygen, but stromatolites release oxygen as a by-product
of photosynthesis. In the Archean and more so in the Proterozoic, they increased oxygen in Earth's
atmosphere.
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Which of the following statements about chain reactions is true?
A. The key requirement for a chain reaction is that more neutrons are produced than that are absorbed. B. Three or more neutrons must be released to sustain a chain reaction. C. Only uranium isotopes are capable of supporting a chain reaction. D. A chain reaction will only take place when a critical mass of material has been assembled. E. It is not possible to stop or control a chain reaction once it has been started.
Storm surges are most intense
A) on the left side of the hurricane. B) on the right side of the hurricane. C) in the middle of the hurricane. D) just after the trailing edge of the hurricane has passed.
It required 88.2 calories to heat 14.3 g of an unknown substance from 24°C to 175°C. What is the specific heat of the unknown?
A) 0.245 cal /g·°C B) 0.317 cal /g·°C C) 0.408 cal /g·°C D) none of these
Real tides in ocean basins feel the effect of the ________.
A. continents B. Coriolis effect C. ocean basin's standing wave D. water depth E. All of these are correct.