### Hotspot Volcanism
Hotspot volcanism refers to volcanic activity that occurs away from tectonic plate boundaries, such as the Hawaiian Islands. Two scientists discuss the mechanism responsible for this phenomenon.
Scientist 1
Hotspot volcanism is driven by deep mantle plumes—narrow columns of hot, solid mantle rock that rise from the core-mantle boundary (approximately deep). Because these plumes originate from deep within the Earth, their locations remain stationary relative to the moving lithospheric plates above. As a tectonic plate slides over a stationary plume, a linear chain of volcanoes is formed, with volcano age increasing progressively with distance from the active hotspot. The high temperature of the plume causes localized melting of the lithosphere.
Scientist 2
Hotspot volcanism is a passive process caused by cracks and tension in the tectonic plates themselves. Stress within a plate causes the lithosphere to stretch and fracture. This fracturing allows magma from the shallow upper mantle (less than deep) to escape to the surface. These hotspots are not stationary; rather, their locations migrate along with the stress patterns of the plates. The linear chains of volcanoes result from the propagation of lithospheric cracks over time, meaning the age progression is determined by crack propagation velocity, not plate velocity.
Based on the passage, match each point of disagreement between Scientist 1 and Scientist 2 to the correct pair of contrasting viewpoints.
- The depth of origin for hotspot magmaDeep core-mantle boundary () vs. shallow upper mantle (less than )
- The mobility of the hotspot sourceStationary vs. migrating with plate stress patterns
- The factor determining the rate of age progression in a volcanic chainTectonic plate velocity vs. lithospheric crack propagation velocity