4. Tectonic plates are part of the * upper mantle continental and oceanic crust lower mantle continental crust only

Tectonic plates are primarily comprised of the lithosphere, which includes both the continental and oceanic crust along with the uppermost portion of the mantle. These plates float atop the semi-fluid asthenosphere, allowing them to move and interact, leading to fascinating geological phenomena such as earthquakes, volcanic activity, and mountain formation! In real-world terms, understanding tectonic plates is crucial for disaster preparedness. Regions along plate boundaries are often prone to seismic activity. For instance, cities like San Francisco and Tokyo have developed stringent building codes and early warning systems in response to their high risk of earthquakes — showcasing how geology and urban planning collide for safety!