Name _______________________________________________ period _________________ Earthquake/Volcano Study Guide For each of the diagrams describe the type of stress affecting them, the type of fault associated with them, and the type of plate boundary associated with them. Stress _Shear Fault _Strike Slip Boundary _Transform Stress _Tension Fault _Normal Fault Boundary _Divergent Stress _Compression Fault _Reverse Fault Boundary _Convergent Stress _Compression Fault _Reverse Fault Boundary _Convergent Stress _Tension Fault _Normal Fault Boundary _Divergent Name _______________________________________________ period _________________ Stress _Shear Fault _Strike Slip Fault Boundary _Transform What is an Earthquakes epicenter? It is the location on the surface of the Earth directly above the first movement of a fault. It is where the shaking from an Earthquake is normally the worst. What are the 2 types of Earthquake waves needed to calculate the distance to an Earthquake’s epicenter? Primary (P) waves, and Secondary (S) waves What are the differences between those 2 waves? Primary waves are the fastest, and arrive at earthquake monitoring stations first. P waves are compression waves and vibrate parallel to the direction of the wave. S waves are slower, and vibrate perpendicular to the direction of the wave. Describe why 3 Earthquake monitoring stations are needed to find the epicenter of an Earthquake? By measuring the time difference between the arrival of the “P” & “S” waves the distance to the earthquake’s epicenter can be calculated, but the direction can not. Using the distance from 3 stations the location can be determined by drawing 3 circles around the stations using the distance as the radius. Name _______________________________________________ period _________________ What Earthquake scale is the best, and why is it the best? _Moment Magnitude Why? The Moment magnitude scale calculates the total energy released from an earthquake, the others use only damage to structures or just earthquake waves. Where are most earthquakes located? _Plate Boundaries Why do they happen there? That is where plates interact the most. They grind against each other, get stuck, and slip. Label the diagram: 8) _Pipe 9) _Crater 10) _Vent 11) _Lava Flow 12) _Magma Chamber Why does magma rise through the crust? It is less dense than the solid rock above it. How do Volcanoes form along convergent boundaries? Volcanoes at convergent boundaries form from the subduction of oceanic crust. As the crust sinks into the mantle it brings water and other materials down into the mantle with it. As it melts it works its way back up through the crust forming a volcano on the continent, or an island arc in the ocean. Because the magma is cooler, has more gas and silca, these volcanoes can be very violent. Why do geologists monitor earthquake activity near volcanoes? Increasing earthquake activity and the intensity of the earthquake waves tell scientists when a volcanic eruption will happen. Describe how volcanoes form at a hot spot under oceanic crust: A hot spot is a place in the mantle that is much hotter than the rest of the mantle. It is hot enough to melt through the thin oceanic crust and erupt onto the ocean floor. Over many years the eruptions build up an island in the ocean. Eventually Name _______________________________________________ period _________________ the crust moves due to plate tectonics off of the hot spot and the volcano becomes extinct. Which means it will not erupt again. Describe a Shield volcano, how it forms, and the type of magma it normally has: A shield volcano normally forms from a hot spot in the mantle. The magma comes mainly from the mantle, and is low in silica and trapped gases- but is very hot. This makes for low viscosity magma, and gentle eruptions of fast moving lava that forms a flattened shape of a shield. Describe a Cinder Cone volcano, how it forms, and the types of magma it normally has: A cinder cone volcano forms mainly from eruptions of ash, and not much lava. They are usually the result of subduction of an oceanic plate, but can also form on the flanks of bigger volcanoes. The magma is typically cooler, has a lot of trapped gases, and is high in silica content. That combination often results in violent eruptions and a very steep cone shaped volcano. Describe a Composite volcano, how it forms, and the types of magma it normally has: A composite volcano normally forms from subduction of an oceanic plate. The oceanic plate subduction produces cooler magma that is high in silica and trapped gases. The magma works its way to the surface where it erupts. It can have quiet eruptions of lava, and more violent eruptions of ash. It has the classic volcano shape.