Download Study Questions on Planetary Science - Midterm Exam | EART 160 and more Exams Geology in PDF only on Docsity! EART160 MIDTERM Mon 9 th Feb 2009 Answer QUESTION 1 and ONE out of questions 2-4. If you attempt more than one, you’ll get credit for the best answer. Show all your working for maximum credit. You have until 12:10pm to complete the test. No calculators. 1. a) Name two different observations that allow us to infer the composition of the original solar nebula (2) b) How long does it take a lava flow 10 km long and 10 m thick to cool? (2) c) Sketch how pressure and gravity vary with radial distance inside a uniform-density planet (2) d) Name four solar system bodies that might be expected to have aeolian deposits (2) e) The heat flow at the Earth’s surface is 30 mWm -2 and the thermal conductivity of crustal material is 3 Wm -1 K -1 . What is the temperature gradient in the crust (in K/km)? (2) f) Explain the physics behind the greenhouse effect which keeps Earth and Venus warm (2) g) If a planet cools by 20 K and has a thermal expansivity of 3x10 -5 K -1 , what is the magnitude of the compressional stresses? Assume Young’s modulus=100 GPa (2) h) Give two reasons why bodies in the outer solar system grow more slowly than in the inner solar system during accretion (2) i) The Moon has a smaller gravity than Mars, but a similar elastic thickness. Explain whether mountains are more likely to be isostatically compensated on the Moon or Mars. (2) j) Give two reasons why a planet might show a lack of small impact craters (2) (20 total) 2. Here we’re going to consider impact craters. a) Consider a hemispherical crater of radius R. If the density of excavated material is e, write down an expression for the mass of material excavated (1). b) In making the crater, this material is raised vertically by a distance R and the acceleration due to gravity is g. Write down an expression for the gravitational potential energy required to lift the material. (1)
