Question

purgatory chasm is a rock formation in massachusetts. it is made of gneiss, which formed through the heating and squeezing of rock. scientists are not sure how the chasm formed. some scientists think it was formed by erosion due to ice. others think it was formed as a result of a large earthquake. what type of rock is purgatory chasm made of? igneous metamorphic sedimentary

Explanation:

文中提到Purgatory Chasm由片麻岩（gneiss）构成，片麻岩是通过岩石的加热和挤压形成的，这是变质岩（metamorphic rock）的形成方式。

Answer:

metamorphic