Gum disease generally develops because of improper brushing and flossing habits, although underlying medical conditions may have a correlation to greater incidence. The bacteria that are found in the mouth as a result of these poor habits begin to affect the surrounding bone and tissues below the gumline.
Most earthquakes occur at the boundaries where the plates meet. In fact, the locations of earthquakes and the kinds of ruptures they produce help scientists define the plate boundaries. There are three types of plate boundaries: spreading zones, transform faults, and subduction zones.
Tsunamis occur after an earthquake. The earthquake can occur under a city (ex. The New Madrid Missouri fault line; or the Los Angeles area's fault lines), but many occur on the ocean or sea floor.n average, two tsunamis occur per year. Approximately every 15  years a destructive, ocean-wide tsunami occurs. Tsunami's occur  when an earthquake causes a significant ver â¦ tical deformation of the  seafloor.