Seismologists Kaiqing Yuan and Barbara Romanowicz have proposed that the magma fueling Iceland’s more than 30 active volcano systems emerges from deep within Earth. The great depths involved—nearly 3,000 km—mark Iceland’s volcanoes as extreme outliers; _______many of Earth’s volcanoes are fed by shallow pockets of magma found less than 15 km below the surface.
Which choice completes the text with the most logical transition?
Explanation
Context: Seismologists report that the magma feeding Iceland's volcanoes rises from nearly 3,000 km down, marking them as extreme outliers. The blank precedes the depth typical of other volcanoes.
Answer: A) indeed,
Why? The claim is that Iceland's volcanoes are outliers, and the fact that most volcanoes draw on magma less than 15 km below the surface shows just how far from the norm 3,000 km is. The transition must present that figure as confirming evidence.
Traps:
- B) "nevertheless" would set the typical depth against the outlier claim, but the comparison supports that claim.
- C) "in addition" treats the shallow-magma fact as a separate point, when it exists only to measure Iceland against the norm.
- D) "consequently" makes other volcanoes' shallow magma a result of Iceland's depth, and no such causal relationship exists.