In the context of plate tectonic theory, the Earth's lithosphere is broken into large, rigid plates that move relative to each other, interacting at their boundaries. There are three major types of plate boundaries: 1. Divergent Plate Boundaries: These occur where two tectonic plates move away from each other. As the plates separate, magma from the mantle rises to fill the gap, creating new crustal material. This process is called seafloor spreading. Geological Features: Characterized by mid-ocean ridges (like the Mid-Atlantic Ridge), rift valleys (like the East African Rift Valley), and frequent but generally shallow earthquakes and volcanic activity*. 2. Convergent Plate Boundaries: These occur where two tectonic plates move towards each other and collide. The outcome depends on the type of crust involved (oceanic or continental). Oceanic-Oceanic Convergence: One oceanic plate subducts (slides beneath) the other, forming an oceanic trench and a chain of volcanic islands* (island arc). Oceanic-Continental Convergence: The denser oceanic plate subducts beneath the lighter continental plate, creating an oceanic trench and a chain of volcanoes on the continent (continental arc) and mountain ranges*. Continental-Continental Convergence: Neither plate subducts significantly due to similar densities, resulting in intense folding and faulting that forms very large mountain ranges* (like the Himalayas). Geological Features: Marked by trenches, volcanoes, mountain ranges, and powerful earthquakes*. 3. Transform Plate Boundaries: These occur where two tectonic plates slide horizontally past each other without creating or destroying crust. The plates grind against each other, building up stress. Geological Features: Characterized by transform faults (like the San Andreas Fault in California) and frequent, often strong, but generally shallow earthquakes*. There is typically no significant volcanic activity or mountain building directly associated with these boundaries.