What conclusion would you draw if a seismogram from a particular seismic station showed only P waves? Why is it better to use data from three or more seismic stations to find the epicenter of an earthquake? How does the time between the arrival of S and P waves relate to the distance of the station to the epicenter?

Ageologist is working in an area with exposed sedimentary rocks and finds a well exposed sequence of stratified rocks. as he works through a thick sequence of limestone, he sees abundant large clam fossils that produce an interlocking texture suggesting a reef, but within the limestone section these clams disappear and the overlying limestone is made up primarily of fragments of corals. he now moves 50 km away and finds limestones interbedded with shales, and the limestones contain the same clam fossils he had seen previously 50 km away. as he continues through this section, the rocks become entirely limestone, and the clams disappear again with coral fossils above forming a reef structure. he concludes