Three types of boundaries and their consequences
Convergent boundaries (plates colliding) create mountains and deep trenches, and drive earthquakes and volcanism. Divergent boundaries (plates pulling apart) are where new crust forms and mid-ocean ridges occur. Transform boundaries (plates sliding sideways) produce earthquakes without volcanism. The Pacific Ring of Fire is mostly convergent, making it the most seismically active zone on Earth. The Mid-Atlantic Ridge is divergent, actively spreading and creating new seafloor.
Plate tectonics and human risk
Major cities sit near plate boundaries: Tokyo, San Francisco, Manila, Christchurch, and Istanbul are all at high seismic risk. The 2011 Tohoku earthquake and tsunami was caused by a subduction zone (convergent boundary). Understanding global plate boundaries is crucial for earthquake prediction, building codes, and hazard planning. The boundaries also concentrate mineral resources and geothermal energy, shaping both natural hazards and economic opportunity.