Clams, sponges, and crabs are all examples of ________ organisms
Fill in the blank(s) with correct word
benthos
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Consider the escape speed for a rocket on the Moon returning to Earth. Escape speed from Moon to Earth is
A. less than from Earth. B. about the same as from Earth. C. more than from Earth. D. none of the above
Hydropower
A. provides about 90% of the electricity in Europe. B. is most important in rivers and streams. C. uses the potential energy of large standing water bodies to produce electricity. D. can emit methane from the decomposition of submerged vegetation in reservoirs. E. is expected to grow in large-scale plants in the future.
The original reactor built in 1942 was just "barely" critical because the natural uranium that was used contained less than 1% of the fissionable isotope U-235 (half-life 713 million years). What if, in 1942, the Earth had been 9 billion years old instead of 4.5 billion years old? Would this reactor have reached critical stage with natural uranium? Why?
A. No. The increased age of the Earth would mean that there would be a much smaller percentage of U-235, thus not enough for the reactor to reach critical stage. B. No. The age of the Earth has nothing to do with the reactor reaching critical stage with U-235. C. No. 1% of the fissionable isotope U-235 is insufficient for the reactor to reach critical stage no matter what the age of the Earth. D. Yes. If the Earth had been twice as old there would have then been twice as much fissionable U-235 present and the reactor would have reached critical stage.
Based on the principle of Baked Contacts, which of the following statements are right?
a. If an igneous intrusion "bakes" surrounding rocks, then the rock that has been baked must be younger than the intrusion b. The intrusion geologic feature is younger than the original rock c. Baked contacts do not provide directly the relative age, because of the later erosion d. When pluton (one igneous rock) was found to bake the adjacent rock, then this pluton is relatively younger e. Both b and d