1. Test question 8.1 • During earth quakes, p waves travel at 6 km/s which is faster than s waves at 4 km/s. At a distance of 24 km from the epicenter, • vPwaves arrive before s waves by 2 sec • xPwaves arrive before s waves by 4 sec • xThereis no time delay between p and s waves • xSwaves arrive 4 sec before P waves

2. Test question 8.2 • The cores of terrestrial planets are composed mostly of iron and their mantle mostly silicates because: • xIronwas accreted first and silicates fall later • vIronsunk to the bottom and silicates to the top after they become molten • xSilicatescondensed out of the air which was released from the iron • xSilicatesare harder to destroy and form a protective shield around the iron core

3. Test question 8.3 • The core of the moon is cold whereas that of that of the Earth is molten because • vThemoon has a smaller volume and loses heat per unit gram faster than the Earth • xThemoon has much less radioactive isotopes • xThemoon is not heated by the Sun because it is only around during the day • xThe moon is further away from the Sun than the Earth

4. Test question 8.4 • The moon has many more craters than the earth because • xItwas bombarded more frequently than the Earth, • xThe moon’s surface has always been solid, • xThemoon is older than the Earth • vThereis much less erosion on the moon.