Geology Plate Tectonic Theory Questions Questions: 1. Why does Central America have no active volcanoes? 2. Why are there active volcanoes on the ocean floor? 3. Why are there large, deep troughs (or grooves) in the ocean floor? 4. Explain why Japan is a country that experiences large earthquakes. 5. What would be further down in the mantle, continents or the ocean floor? 6. Extension Question: Explain how a tsunami can occur.