Toss Up - Earth Science - Multiple Choice

A group of small volcanoes, called the petit spot volcanoes, was recently found. What makes this find so unusual is they are believed to be formed:
W) from asthenosphere material squeezing through cracks caused by bending in Earth’s crust
X) from plumes rising rapidly from the boundary between Earth’s core and mantle
Y) at a convergent plate boundary
Z) at a mid-ocean ridge