Locate an Epicenter From Three Stations

Start with the mantle convection diagram for the big picture. Use the Hawaii and subduction sheets as graphing labs, and save the epicenter sheet for a compass activity.

Read S minus P lag times for three stations and draw circles to locate an earthquake epicenter. The lag is the time between the P waves and the slower S waves reaching a station. The farther the station is from the epicenter, the longer the lag. The directions on the page read: Read each station's distance from the graph and write it in the table. Use a compass and the scale bar to draw a circle of that distance around each station, and mark the epicenter with an X where the circles cross. Then answer questions 1 to 4. An answer key is included.

Yes, both. We made it for 8th grade Earth science, and it works the same at home or at school. At home, a student can work through it alone and then go over it with you, which shows quickly what is solid and what needs another look. In class it works as independent practice, homework or a warm-up, and you can print one copy or a full set.

A column of hot rock rises from the mantle and stays in about the same place while the plate above moves. Each volcano forms over the hot spot and is carried away. In Hawaii, the volcanoes get older toward the northwest.

At a subduction zone, the denser ocean plate sinks under the other plate at an angle. Quakes happen along the sinking plate, so they are deeper the farther they are from the trench. The subduction sheet plots depth against distance.

Heat from the core drives slow convection currents in the mantle. Rising rock at a mid-ocean ridge pushes plates apart, and a cold sinking slab at a trench pulls its plate along. Label Mantle Convection and Plate Motion labels both.