Final answer:
Hotspots can be expressed through flood basalts, explosive calderas, and linear island chains.
Step-by-step explanation:
The expression of a hot spot in the context of volcanic activity can be seen in flood basalts, explosive calderas, and linear island chains. Flood basalts occur when hotspots are located under oceanic crust, resulting in the production of extensive layers of basaltic lava. Explosive calderas are formed when hotspots are located under continental crust, leading to both basaltic and rhyolitic volcanic eruptions. Linear island chains are formed when tectonic plates move over hotspots, resulting in a trail of volcanic islands.