Question

Using one to two sentences, explain how the movement of tectonic plates helps turn sedimentary rocks into metamorphic rocks.

Which processes must happen for sand to eventually become metamorphic rock? Name and briefly describe the process in one to two sentences.

Answer 1

When tectonic plates converge, subduct, or build mountains they bury and squeeze sedimentary rocks, exposing them to high heat, pressure, and deformation that cause minerals to recrystallize and form metamorphic rocks.

Processes for sand → metamorphic rock:
- Weathering and erosion: Existing rock is broken down into sand-sized grains by wind, water, and ice, which are then picked up and moved.
- Transport and deposition: The sand grains are carried to a basin or shoreline and settle out as a layer of sediment.
- Compaction and cementation (lithification): Buried under more sediment, the sand is compacted and minerals precipitate to cement the grains into sandstone.
- Burial, heating and pressure (metamorphism): Tectonic burial or collision increases temperature and pressure, causing recrystallization and reorientation of minerals (and sometimes new mineral growth), transforming sandstone into a metamorphic rock such as quartzite.