1. FALSE; The plate tectonics move due to convection currents of the mantle; the cooler upper mantle descends while the hotter lower mantles ascend. The heat that drives these convection currents emanated from the core of the earth (not the sun).
2. TRUE; The liquid core of the earth is unable to transmit the shear waves of the S- waves of an earthquake due to its elasticity. In addition, due to its different density from that of the solid inner core, the P waves are refracted hence are bent away from the earth surface directly above the earthquake zone. This, therefore, creates a shadow zone in the angular distances of 104 to 140 degrees from the epicenter of an earthquake.
3. FALSE; Tectonic plates are rigid and their collision is inelastic. The most damage is caused at convergence boundaries where two tectonic plates moving in opposite direction collide causing one to submerge under the other. These regions are prone to earthquakes of high magnitudes on the Richter scale (an example is the Ring of Fire).
4. FALSE; Earthquakes can also be caused by other volcanic events such as volcanic eruptions. As the magma squeezes in the magma chambers and the pressure suddenly releases, an earthquake will result. Manmade activities such as nuclear detonation can also cause an earthquake.
5. TRUE; Earthquakes occur from the sudden release of built-up pressure. An example is when two tectonic plates, that are stuck together when moving against one another, suddenly release. When the pressure in a magma chamber suddenly releases during a volcanic eruption.
6. TRUE; Contour lines are lines used in a topographical map to indicate land that is on the same altitude above sea level. Contour lines can be used to indicate the steepness of a hill or the mountain. The closer the contour lines (that usually have a standard difference of 500 - 1000m) the steeper the sides of the mountain or hill.
7. TRUE; the lithosphere is majorly composed of the crust of the earth while the asthenosphere is majorly the upper portion of the mantle that lies beneath the crust. The lithosphere is rigid while the asthenosphere is fluid. The currents at the asthenosphere drive tectonic plate movements and is the source of magma that reached the earth’s surface.
8. TRUE; The ring of fire is as a result of a subduction zone as the Nazca, Cocos, North American, Carribean, and South American plate continuously collide in the region as they move in opposite directions. This region contributes to approximately 80% of all earthquakes on the planet.
9. FALSE; The Oceanic plate is denser than continental plate because it is heavily percolated with water from the oceans (hence is considered ‘wet’) for millions of years. Nonetheless, the oceanic plate is younger than continental plate due to the phenomenon of seafloor spreading that renews the crust at the divergent boundary as the plate is consumed at convergent boundaries.
10. FALSE; The answer is three (3). The readings on three seismographs located at different locations relative to the earthquake will enable triangulation of the epicenter. The difference in time between the S-waves and P-waves on each seismograph will help deduce the distance of the epicenter from the respective seismograph. By drawing three (3) circles for each seismograph (using this distance as radius), the point the circles overlap is the epicenter.
